[IA64-SGI] SGI Altix cross partition functionality [2/3]

This patch contains the communication module (XPC) for cross partition
communication on a partitioned SGI Altix.
Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/sn/kernel/Makefile

@@ -13,3 +13,5 @@ obj-$(CONFIG_IA64_GENERIC)      += machvec.o
 obj-$(CONFIG_SGI_TIOCX)		+= tiocx.o
 obj-$(CONFIG_IA64_SGI_SN_XP)	+= xp.o
 xp-y				:= xp_main.o xp_nofault.o
+obj-$(CONFIG_IA64_SGI_SN_XP)	+= xpc.o
+xpc-y				:= xpc_main.o xpc_channel.o xpc_partition.o

arch/ia64/sn/kernel/xpc.h

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2004-2005 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+
+
+/*
+ * Cross Partition Communication (XPC) structures and macros.
+ */
+
+#ifndef _IA64_SN_KERNEL_XPC_H
+#define _IA64_SN_KERNEL_XPC_H
+
+
+#include <linux/config.h>
+#include <linux/interrupt.h>
+#include <linux/sysctl.h>
+#include <linux/device.h>
+#include <asm/pgtable.h>
+#include <asm/processor.h>
+#include <asm/sn/bte.h>
+#include <asm/sn/clksupport.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/mspec.h>
+#include <asm/sn/shub_mmr.h>
+#include <asm/sn/xp.h>
+
+
+/*
+ * XPC Version numbers consist of a major and minor number. XPC can always
+ * talk to versions with same major #, and never talk to versions with a
+ * different major #.
+ */
+#define _XPC_VERSION(_maj, _min)	(((_maj) << 4) | ((_min) & 0xf))
+#define XPC_VERSION_MAJOR(_v)		((_v) >> 4)
+#define XPC_VERSION_MINOR(_v)		((_v) & 0xf)
+
+
+/*
+ * The next macros define word or bit representations for given
+ * C-brick nasid in either the SAL provided bit array representing
+ * nasids in the partition/machine or the AMO_t array used for
+ * inter-partition initiation communications.
+ *
+ * For SN2 machines, C-Bricks are alway even numbered NASIDs.  As
+ * such, some space will be saved by insisting that nasid information
+ * passed from SAL always be packed for C-Bricks and the
+ * cross-partition interrupts use the same packing scheme.
+ */
+#define XPC_NASID_W_INDEX(_n)	(((_n) / 64) / 2)
+#define XPC_NASID_B_INDEX(_n)	(((_n) / 2) & (64 - 1))
+#define XPC_NASID_IN_ARRAY(_n, _p) ((_p)[XPC_NASID_W_INDEX(_n)] & \
+				    (1UL << XPC_NASID_B_INDEX(_n)))
+#define XPC_NASID_FROM_W_B(_w, _b) (((_w) * 64 + (_b)) * 2)
+
+#define XPC_HB_DEFAULT_INTERVAL		5	/* incr HB every x secs */
+#define XPC_HB_CHECK_DEFAULT_TIMEOUT	20	/* check HB every x secs */
+
+/* define the process name of HB checker and the CPU it is pinned to */
+#define XPC_HB_CHECK_THREAD_NAME	"xpc_hb"
+#define XPC_HB_CHECK_CPU		0
+
+/* define the process name of the discovery thread */
+#define XPC_DISCOVERY_THREAD_NAME	"xpc_discovery"
+
+
+#define XPC_HB_ALLOWED(_p, _v)	((_v)->heartbeating_to_mask & (1UL << (_p)))
+#define XPC_ALLOW_HB(_p, _v)	(_v)->heartbeating_to_mask |= (1UL << (_p))
+#define XPC_DISALLOW_HB(_p, _v)	(_v)->heartbeating_to_mask &= (~(1UL << (_p)))
+
+
+/*
+ * Reserved Page provided by SAL.
+ *
+ * SAL provides one page per partition of reserved memory.  When SAL
+ * initialization is complete, SAL_signature, SAL_version, partid,
+ * part_nasids, and mach_nasids are set.
+ *
+ * Note: Until vars_pa is set, the partition XPC code has not been initialized.
+ */
+struct xpc_rsvd_page {
+	u64 SAL_signature;	/* SAL unique signature */
+	u64 SAL_version;	/* SAL specified version */
+	u8 partid;		/* partition ID from SAL */
+	u8 version;
+	u8 pad[6];		/* pad to u64 align */
+	u64 vars_pa;
+	u64 part_nasids[XP_NASID_MASK_WORDS] ____cacheline_aligned;
+	u64 mach_nasids[XP_NASID_MASK_WORDS] ____cacheline_aligned;
+};
+#define XPC_RP_VERSION _XPC_VERSION(1,0) /* version 1.0 of the reserved page */
+
+#define XPC_RSVD_PAGE_ALIGNED_SIZE \
+			(L1_CACHE_ALIGN(sizeof(struct xpc_rsvd_page)))
+
+
+/*
+ * Define the structures by which XPC variables can be exported to other
+ * partitions. (There are two: struct xpc_vars and struct xpc_vars_part)
+ */
+
+/*
+ * The following structure describes the partition generic variables
+ * needed by other partitions in order to properly initialize.
+ *
+ * struct xpc_vars version number also applies to struct xpc_vars_part.
+ * Changes to either structure and/or related functionality should be
+ * reflected by incrementing either the major or minor version numbers
+ * of struct xpc_vars.
+ */
+struct xpc_vars {
+	u8 version;
+	u64 heartbeat;
+	u64 heartbeating_to_mask;
+	u64 kdb_status;		/* 0 = machine running */
+	int act_nasid;
+	int act_phys_cpuid;
+	u64 vars_part_pa;
+	u64 amos_page_pa;	/* paddr of page of AMOs from MSPEC driver */
+	AMO_t *amos_page;	/* vaddr of page of AMOs from MSPEC driver */
+	AMO_t *act_amos;	/* pointer to the first activation AMO */
+};
+#define XPC_V_VERSION _XPC_VERSION(3,0) /* version 3.0 of the cross vars */
+
+#define XPC_VARS_ALIGNED_SIZE  (L1_CACHE_ALIGN(sizeof(struct xpc_vars)))
+
+/*
+ * The following structure describes the per partition specific variables.
+ *
+ * An array of these structures, one per partition, will be defined. As a
+ * partition becomes active XPC will copy the array entry corresponding to
+ * itself from that partition. It is desirable that the size of this
+ * structure evenly divide into a cacheline, such that none of the entries
+ * in this array crosses a cacheline boundary. As it is now, each entry
+ * occupies half a cacheline.
+ */
+struct xpc_vars_part {
+	u64 magic;
+
+	u64 openclose_args_pa;	/* physical address of open and close args */
+	u64 GPs_pa;		/* physical address of Get/Put values */
+
+	u64 IPI_amo_pa;		/* physical address of IPI AMO_t structure */
+	int IPI_nasid;		/* nasid of where to send IPIs */
+	int IPI_phys_cpuid;	/* physical CPU ID of where to send IPIs */
+
+	u8 nchannels;		/* #of defined channels supported */
+
+	u8 reserved[23];	/* pad to a full 64 bytes */
+};
+
+/*
+ * The vars_part MAGIC numbers play a part in the first contact protocol.
+ *
+ * MAGIC1 indicates that the per partition specific variables for a remote
+ * partition have been initialized by this partition.
+ *
+ * MAGIC2 indicates that this partition has pulled the remote partititions
+ * per partition variables that pertain to this partition.
+ */
+#define XPC_VP_MAGIC1	0x0053524156435058L  /* 'XPCVARS\0'L (little endian) */
+#define XPC_VP_MAGIC2	0x0073726176435058L  /* 'XPCvars\0'L (little endian) */
+
+
+
+/*
+ * Functions registered by add_timer() or called by kernel_thread() only
+ * allow for a single 64-bit argument. The following macros can be used to
+ * pack and unpack two (32-bit, 16-bit or 8-bit) arguments into or out from
+ * the passed argument.
+ */
+#define XPC_PACK_ARGS(_arg1, _arg2) \
+			((((u64) _arg1) & 0xffffffff) | \
+			((((u64) _arg2) & 0xffffffff) << 32))
+
+#define XPC_UNPACK_ARG1(_args)	(((u64) _args) & 0xffffffff)
+#define XPC_UNPACK_ARG2(_args)	((((u64) _args) >> 32) & 0xffffffff)
+
+
+
+/*
+ * Define a Get/Put value pair (pointers) used with a message queue.
+ */
+struct xpc_gp {
+	s64 get;	/* Get value */
+	s64 put;	/* Put value */
+};
+
+#define XPC_GP_SIZE \
+		L1_CACHE_ALIGN(sizeof(struct xpc_gp) * XPC_NCHANNELS)
+
+
+
+/*
+ * Define a structure that contains arguments associated with opening and
+ * closing a channel.
+ */
+struct xpc_openclose_args {
+	u16 reason;		/* reason why channel is closing */
+	u16 msg_size;		/* sizeof each message entry */
+	u16 remote_nentries;	/* #of message entries in remote msg queue */
+	u16 local_nentries;	/* #of message entries in local msg queue */
+	u64 local_msgqueue_pa;	/* physical address of local message queue */
+};
+
+#define XPC_OPENCLOSE_ARGS_SIZE \
+	      L1_CACHE_ALIGN(sizeof(struct xpc_openclose_args) * XPC_NCHANNELS)
+
+
+
+/* struct xpc_msg flags */
+
+#define	XPC_M_DONE		0x01	/* msg has been received/consumed */
+#define	XPC_M_READY		0x02	/* msg is ready to be sent */
+#define	XPC_M_INTERRUPT		0x04	/* send interrupt when msg consumed */
+
+
+#define XPC_MSG_ADDRESS(_payload) \
+		((struct xpc_msg *)((u8 *)(_payload) - XPC_MSG_PAYLOAD_OFFSET))
+
+
+
+/*
+ * Defines notify entry.
+ *
+ * This is used to notify a message's sender that their message was received
+ * and consumed by the intended recipient.
+ */
+struct xpc_notify {
+	struct semaphore sema;		/* notify semaphore */
+	u8 type;			/* type of notification */
+
+	/* the following two fields are only used if type == XPC_N_CALL */
+	xpc_notify_func func;		/* user's notify function */
+	void *key;			/* pointer to user's key */
+};
+
+/* struct xpc_notify type of notification */
+
+#define	XPC_N_CALL		0x01	/* notify function provided by user */
+
+
+
+/*
+ * Define the structure that manages all the stuff required by a channel. In
+ * particular, they are used to manage the messages sent across the channel.
+ *
+ * This structure is private to a partition, and is NOT shared across the
+ * partition boundary.
+ *
+ * There is an array of these structures for each remote partition. It is
+ * allocated at the time a partition becomes active. The array contains one
+ * of these structures for each potential channel connection to that partition.
+ *
+ * Each of these structures manages two message queues (circular buffers).
+ * They are allocated at the time a channel connection is made. One of
+ * these message queues (local_msgqueue) holds the locally created messages
+ * that are destined for the remote partition. The other of these message
+ * queues (remote_msgqueue) is a locally cached copy of the remote partition's
+ * own local_msgqueue.
+ *
+ * The following is a description of the Get/Put pointers used to manage these
+ * two message queues. Consider the local_msgqueue to be on one partition
+ * and the remote_msgqueue to be its cached copy on another partition. A
+ * description of what each of the lettered areas contains is included.
+ *
+ *
+ *                     local_msgqueue      remote_msgqueue
+ *
+ *                        |/////////|      |/////////|
+ *    w_remote_GP.get --> +---------+      |/////////|
+ *                        |    F    |      |/////////|
+ *     remote_GP.get  --> +---------+      +---------+ <-- local_GP->get
+ *                        |         |      |         |
+ *                        |         |      |    E    |
+ *                        |         |      |         |
+ *                        |         |      +---------+ <-- w_local_GP.get
+ *                        |    B    |      |/////////|
+ *                        |         |      |////D////|
+ *                        |         |      |/////////|
+ *                        |         |      +---------+ <-- w_remote_GP.put
+ *                        |         |      |////C////|
+ *      local_GP->put --> +---------+      +---------+ <-- remote_GP.put
+ *                        |         |      |/////////|
+ *                        |    A    |      |/////////|
+ *                        |         |      |/////////|
+ *     w_local_GP.put --> +---------+      |/////////|
+ *                        |/////////|      |/////////|
+ *
+ *
+ *	    ( remote_GP.[get|put] are cached copies of the remote
+ *	      partition's local_GP->[get|put], and thus their values can
+ *	      lag behind their counterparts on the remote partition. )
+ *
+ *
+ *  A - Messages that have been allocated, but have not yet been sent to the
+ *	remote partition.
+ *
+ *  B - Messages that have been sent, but have not yet been acknowledged by the
+ *      remote partition as having been received.
+ *
+ *  C - Area that needs to be prepared for the copying of sent messages, by
+ *	the clearing of the message flags of any previously received messages.
+ *
+ *  D - Area into which sent messages are to be copied from the remote
+ *	partition's local_msgqueue and then delivered to their intended
+ *	recipients. [ To allow for a multi-message copy, another pointer
+ *	(next_msg_to_pull) has been added to keep track of the next message
+ *	number needing to be copied (pulled). It chases after w_remote_GP.put.
+ *	Any messages lying between w_local_GP.get and next_msg_to_pull have
+ *	been copied and are ready to be delivered. ]
+ *
+ *  E - Messages that have been copied and delivered, but have not yet been
+ *	acknowledged by the recipient as having been received.
+ *
+ *  F - Messages that have been acknowledged, but XPC has not yet notified the
+ *	sender that the message was received by its intended recipient.
+ *	This is also an area that needs to be prepared for the allocating of
+ *	new messages, by the clearing of the message flags of the acknowledged
+ *	messages.
+ */
+struct xpc_channel {
+	partid_t partid;		/* ID of remote partition connected */
+	spinlock_t lock;		/* lock for updating this structure */
+	u32 flags;			/* general flags */
+
+	enum xpc_retval reason;		/* reason why channel is disconnect'g */
+	int reason_line;		/* line# disconnect initiated from */
+
+	u16 number;			/* channel # */
+
+	u16 msg_size;			/* sizeof each msg entry */
+	u16 local_nentries;		/* #of msg entries in local msg queue */
+	u16 remote_nentries;		/* #of msg entries in remote msg queue*/
+
+	void *local_msgqueue_base;	/* base address of kmalloc'd space */
+	struct xpc_msg *local_msgqueue;	/* local message queue */
+	void *remote_msgqueue_base;	/* base address of kmalloc'd space */
+	struct xpc_msg *remote_msgqueue;/* cached copy of remote partition's */
+					/* local message queue */
+	u64 remote_msgqueue_pa;		/* phys addr of remote partition's */
+					/* local message queue */
+
+	atomic_t references;		/* #of external references to queues */
+
+	atomic_t n_on_msg_allocate_wq;   /* #on msg allocation wait queue */
+	wait_queue_head_t msg_allocate_wq; /* msg allocation wait queue */
+
+	/* queue of msg senders who want to be notified when msg received */
+
+	atomic_t n_to_notify;		/* #of msg senders to notify */
+	struct xpc_notify *notify_queue;/* notify queue for messages sent */
+
+	xpc_channel_func func;		/* user's channel function */
+	void *key;			/* pointer to user's key */
+
+	struct semaphore msg_to_pull_sema; /* next msg to pull serialization */
+	struct semaphore teardown_sema;    /* wait for teardown completion */
+
+	struct xpc_openclose_args *local_openclose_args; /* args passed on */
+					/* opening or closing of channel */
+
+	/* various flavors of local and remote Get/Put values */
+
+	struct xpc_gp *local_GP;	/* local Get/Put values */
+	struct xpc_gp remote_GP;	/* remote Get/Put values */
+	struct xpc_gp w_local_GP;	/* working local Get/Put values */
+	struct xpc_gp w_remote_GP;	/* working remote Get/Put values */
+	s64 next_msg_to_pull;		/* Put value of next msg to pull */
+
+	/* kthread management related fields */
+
+// >>> rethink having kthreads_assigned_limit and kthreads_idle_limit; perhaps
+// >>> allow the assigned limit be unbounded and let the idle limit be dynamic
+// >>> dependent on activity over the last interval of time
+	atomic_t kthreads_assigned;	/* #of kthreads assigned to channel */
+	u32 kthreads_assigned_limit; 	/* limit on #of kthreads assigned */
+	atomic_t kthreads_idle;		/* #of kthreads idle waiting for work */
+	u32 kthreads_idle_limit;	/* limit on #of kthreads idle */
+	atomic_t kthreads_active;	/* #of kthreads actively working */
+	// >>> following field is temporary
+	u32 kthreads_created;		/* total #of kthreads created */
+
+	wait_queue_head_t idle_wq;	/* idle kthread wait queue */
+
+} ____cacheline_aligned;
+
+
+/* struct xpc_channel flags */
+
+#define	XPC_C_WASCONNECTED	0x00000001 /* channel was connected */
+
+#define	XPC_C_ROPENREPLY	0x00000002 /* remote open channel reply */
+#define	XPC_C_OPENREPLY		0x00000004 /* local open channel reply */
+#define	XPC_C_ROPENREQUEST	0x00000008 /* remote open channel request */
+#define	XPC_C_OPENREQUEST	0x00000010 /* local open channel request */
+
+#define	XPC_C_SETUP		0x00000020 /* channel's msgqueues are alloc'd */
+#define	XPC_C_CONNECTCALLOUT	0x00000040 /* channel connected callout made */
+#define	XPC_C_CONNECTED		0x00000080 /* local channel is connected */
+#define	XPC_C_CONNECTING	0x00000100 /* channel is being connected */
+
+#define	XPC_C_RCLOSEREPLY	0x00000200 /* remote close channel reply */
+#define	XPC_C_CLOSEREPLY	0x00000400 /* local close channel reply */
+#define	XPC_C_RCLOSEREQUEST	0x00000800 /* remote close channel request */
+#define	XPC_C_CLOSEREQUEST	0x00001000 /* local close channel request */
+
+#define	XPC_C_DISCONNECTED	0x00002000 /* channel is disconnected */
+#define	XPC_C_DISCONNECTING	0x00004000 /* channel is being disconnected */
+
+
+
+/*
+ * Manages channels on a partition basis. There is one of these structures
+ * for each partition (a partition will never utilize the structure that
+ * represents itself).
+ */
+struct xpc_partition {
+
+	/* XPC HB infrastructure */
+
+	u64 remote_rp_pa;		/* phys addr of partition's rsvd pg */
+	u64 remote_vars_pa;		/* phys addr of partition's vars */
+	u64 remote_vars_part_pa;	/* phys addr of partition's vars part */
+	u64 last_heartbeat;		/* HB at last read */
+	u64 remote_amos_page_pa;	/* phys addr of partition's amos page */
+	int remote_act_nasid;		/* active part's act/deact nasid */
+	int remote_act_phys_cpuid;	/* active part's act/deact phys cpuid */
+	u32 act_IRQ_rcvd;		/* IRQs since activation */
+	spinlock_t act_lock;		/* protect updating of act_state */
+	u8 act_state;			/* from XPC HB viewpoint */
+	enum xpc_retval reason;		/* reason partition is deactivating */
+	int reason_line;		/* line# deactivation initiated from */
+	int reactivate_nasid;		/* nasid in partition to reactivate */
+
+
+	/* XPC infrastructure referencing and teardown control */
+
+	u8 setup_state;			/* infrastructure setup state */
+	wait_queue_head_t teardown_wq;	/* kthread waiting to teardown infra */
+	atomic_t references;		/* #of references to infrastructure */
+
+
+	/*
+	 * NONE OF THE PRECEDING FIELDS OF THIS STRUCTURE WILL BE CLEARED WHEN
+	 * XPC SETS UP THE NECESSARY INFRASTRUCTURE TO SUPPORT CROSS PARTITION
+	 * COMMUNICATION. ALL OF THE FOLLOWING FIELDS WILL BE CLEARED. (THE
+	 * 'nchannels' FIELD MUST BE THE FIRST OF THE FIELDS TO BE CLEARED.)
+	 */
+
+
+	u8 nchannels;		   /* #of defined channels supported */
+	atomic_t nchannels_active; /* #of channels that are not DISCONNECTED */
+	struct xpc_channel *channels;/* array of channel structures */
+
+	void *local_GPs_base;	  /* base address of kmalloc'd space */
+	struct xpc_gp *local_GPs; /* local Get/Put values */
+	void *remote_GPs_base;    /* base address of kmalloc'd space */
+	struct xpc_gp *remote_GPs;/* copy of remote partition's local Get/Put */
+				  /* values */
+	u64 remote_GPs_pa;	  /* phys address of remote partition's local */
+				  /* Get/Put values */
+
+
+	/* fields used to pass args when opening or closing a channel */
+
+	void *local_openclose_args_base;  /* base address of kmalloc'd space */
+	struct xpc_openclose_args *local_openclose_args;  /* local's args */
+	void *remote_openclose_args_base; /* base address of kmalloc'd space */
+	struct xpc_openclose_args *remote_openclose_args; /* copy of remote's */
+					  /* args */
+	u64 remote_openclose_args_pa;	  /* phys addr of remote's args */
+
+
+	/* IPI sending, receiving and handling related fields */
+
+	int remote_IPI_nasid;	    /* nasid of where to send IPIs */
+	int remote_IPI_phys_cpuid;  /* phys CPU ID of where to send IPIs */
+	AMO_t *remote_IPI_amo_va;   /* address of remote IPI AMO_t structure */
+
+	AMO_t *local_IPI_amo_va;    /* address of IPI AMO_t structure */
+	u64 local_IPI_amo;	    /* IPI amo flags yet to be handled */
+	char IPI_owner[8];	    /* IPI owner's name */
+	struct timer_list dropped_IPI_timer; /* dropped IPI timer */
+
+	spinlock_t IPI_lock;	    /* IPI handler lock */
+
+
+	/* channel manager related fields */
+
+	atomic_t channel_mgr_requests;	/* #of requests to activate chan mgr */
+	wait_queue_head_t channel_mgr_wq; /* channel mgr's wait queue */
+
+} ____cacheline_aligned;
+
+
+/* struct xpc_partition act_state values (for XPC HB) */
+
+#define	XPC_P_INACTIVE		0x00	/* partition is not active */
+#define XPC_P_ACTIVATION_REQ	0x01	/* created thread to activate */
+#define XPC_P_ACTIVATING	0x02	/* activation thread started */
+#define XPC_P_ACTIVE		0x03	/* xpc_partition_up() was called */
+#define XPC_P_DEACTIVATING	0x04	/* partition deactivation initiated */
+
+
+#define XPC_DEACTIVATE_PARTITION(_p, _reason) \
+			xpc_deactivate_partition(__LINE__, (_p), (_reason))
+
+
+/* struct xpc_partition setup_state values */
+
+#define XPC_P_UNSET		0x00	/* infrastructure was never setup */
+#define XPC_P_SETUP		0x01	/* infrastructure is setup */
+#define XPC_P_WTEARDOWN		0x02	/* waiting to teardown infrastructure */
+#define XPC_P_TORNDOWN		0x03	/* infrastructure is torndown */
+
+
+/*
+ * struct xpc_partition IPI_timer #of seconds to wait before checking for
+ * dropped IPIs. These occur whenever an IPI amo write doesn't complete until
+ * after the IPI was received.
+ */
+#define XPC_P_DROPPED_IPI_WAIT	(0.25 * HZ)
+
+
+#define XPC_PARTID(_p)	((partid_t) ((_p) - &xpc_partitions[0]))
+
+
+
+/* found in xp_main.c */
+extern struct xpc_registration xpc_registrations[];
+
+
+/* >>> found in xpc_main.c only */
+extern struct device *xpc_part;
+extern struct device *xpc_chan;
+extern irqreturn_t xpc_notify_IRQ_handler(int, void *, struct pt_regs *);
+extern void xpc_dropped_IPI_check(struct xpc_partition *);
+extern void xpc_activate_kthreads(struct xpc_channel *, int);
+extern void xpc_create_kthreads(struct xpc_channel *, int);
+extern void xpc_disconnect_wait(int);
+
+
+/* found in xpc_main.c and efi-xpc.c */
+extern void xpc_activate_partition(struct xpc_partition *);
+
+
+/* found in xpc_partition.c */
+extern int xpc_exiting;
+extern int xpc_hb_interval;
+extern int xpc_hb_check_interval;
+extern struct xpc_vars *xpc_vars;
+extern struct xpc_rsvd_page *xpc_rsvd_page;
+extern struct xpc_vars_part *xpc_vars_part;
+extern struct xpc_partition xpc_partitions[XP_MAX_PARTITIONS + 1];
+extern char xpc_remote_copy_buffer[];
+extern struct xpc_rsvd_page *xpc_rsvd_page_init(void);
+extern void xpc_allow_IPI_ops(void);
+extern void xpc_restrict_IPI_ops(void);
+extern int xpc_identify_act_IRQ_sender(void);
+extern enum xpc_retval xpc_mark_partition_active(struct xpc_partition *);
+extern void xpc_mark_partition_inactive(struct xpc_partition *);
+extern void xpc_discovery(void);
+extern void xpc_check_remote_hb(void);
+extern void xpc_deactivate_partition(const int, struct xpc_partition *,
+						enum xpc_retval);
+extern enum xpc_retval xpc_initiate_partid_to_nasids(partid_t, void *);
+
+
+/* found in xpc_channel.c */
+extern void xpc_initiate_connect(int);
+extern void xpc_initiate_disconnect(int);
+extern enum xpc_retval xpc_initiate_allocate(partid_t, int, u32, void **);
+extern enum xpc_retval xpc_initiate_send(partid_t, int, void *);
+extern enum xpc_retval xpc_initiate_send_notify(partid_t, int, void *,
+						xpc_notify_func, void *);
+extern void xpc_initiate_received(partid_t, int, void *);
+extern enum xpc_retval xpc_setup_infrastructure(struct xpc_partition *);
+extern enum xpc_retval xpc_pull_remote_vars_part(struct xpc_partition *);
+extern void xpc_process_channel_activity(struct xpc_partition *);
+extern void xpc_connected_callout(struct xpc_channel *);
+extern void xpc_deliver_msg(struct xpc_channel *);
+extern void xpc_disconnect_channel(const int, struct xpc_channel *,
+					enum xpc_retval, unsigned long *);
+extern void xpc_disconnected_callout(struct xpc_channel *);
+extern void xpc_partition_down(struct xpc_partition *, enum xpc_retval);
+extern void xpc_teardown_infrastructure(struct xpc_partition *);
+
+
+
+static inline void
+xpc_wakeup_channel_mgr(struct xpc_partition *part)
+{
+	if (atomic_inc_return(&part->channel_mgr_requests) == 1) {
+		wake_up(&part->channel_mgr_wq);
+	}
+}
+
+
+
+/*
+ * These next two inlines are used to keep us from tearing down a channel's
+ * msg queues while a thread may be referencing them.
+ */
+static inline void
+xpc_msgqueue_ref(struct xpc_channel *ch)
+{
+	atomic_inc(&ch->references);
+}
+
+static inline void
+xpc_msgqueue_deref(struct xpc_channel *ch)
+{
+	s32 refs = atomic_dec_return(&ch->references);
+
+	DBUG_ON(refs < 0);
+	if (refs == 0) {
+		xpc_wakeup_channel_mgr(&xpc_partitions[ch->partid]);
+	}
+}
+
+
+
+#define XPC_DISCONNECT_CHANNEL(_ch, _reason, _irqflgs) \
+		xpc_disconnect_channel(__LINE__, _ch, _reason, _irqflgs)
+
+
+/*
+ * These two inlines are used to keep us from tearing down a partition's
+ * setup infrastructure while a thread may be referencing it.
+ */
+static inline void
+xpc_part_deref(struct xpc_partition *part)
+{
+	s32 refs = atomic_dec_return(&part->references);
+
+
+	DBUG_ON(refs < 0);
+	if (refs == 0 && part->setup_state == XPC_P_WTEARDOWN) {
+		wake_up(&part->teardown_wq);
+	}
+}
+
+static inline int
+xpc_part_ref(struct xpc_partition *part)
+{
+	int setup;
+
+
+	atomic_inc(&part->references);
+	setup = (part->setup_state == XPC_P_SETUP);
+	if (!setup) {
+		xpc_part_deref(part);
+	}
+	return setup;
+}
+
+
+
+/*
+ * The following macro is to be used for the setting of the reason and
+ * reason_line fields in both the struct xpc_channel and struct xpc_partition
+ * structures.
+ */
+#define XPC_SET_REASON(_p, _reason, _line) \
+	{ \
+		(_p)->reason = _reason; \
+		(_p)->reason_line = _line; \
+	}
+
+
+
+/*
+ * The following set of macros and inlines are used for the sending and
+ * receiving of IPIs (also known as IRQs). There are two flavors of IPIs,
+ * one that is associated with partition activity (SGI_XPC_ACTIVATE) and
+ * the other that is associated with channel activity (SGI_XPC_NOTIFY).
+ */
+
+static inline u64
+xpc_IPI_receive(AMO_t *amo)
+{
+	return FETCHOP_LOAD_OP(TO_AMO((u64) &amo->variable), FETCHOP_CLEAR);
+}
+
+
+static inline enum xpc_retval
+xpc_IPI_send(AMO_t *amo, u64 flag, int nasid, int phys_cpuid, int vector)
+{
+	int ret = 0;
+	unsigned long irq_flags;
+
+
+	local_irq_save(irq_flags);
+
+	FETCHOP_STORE_OP(TO_AMO((u64) &amo->variable), FETCHOP_OR, flag);
+	sn_send_IPI_phys(nasid, phys_cpuid, vector, 0);
+
+	/*
+	 * We must always use the nofault function regardless of whether we
+	 * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
+	 * didn't, we'd never know that the other partition is down and would
+	 * keep sending IPIs and AMOs to it until the heartbeat times out.
+	 */
+	ret = xp_nofault_PIOR((u64 *) GLOBAL_MMR_ADDR(NASID_GET(&amo->variable),
+				xp_nofault_PIOR_target));
+
+	local_irq_restore(irq_flags);
+
+	return ((ret == 0) ? xpcSuccess : xpcPioReadError);
+}
+
+
+/*
+ * IPIs associated with SGI_XPC_ACTIVATE IRQ.
+ */
+
+/*
+ * Flag the appropriate AMO variable and send an IPI to the specified node.
+ */
+static inline void
+xpc_activate_IRQ_send(u64 amos_page, int from_nasid, int to_nasid,
+			int to_phys_cpuid)
+{
+	int w_index = XPC_NASID_W_INDEX(from_nasid);
+	int b_index = XPC_NASID_B_INDEX(from_nasid);
+	AMO_t *amos = (AMO_t *) __va(amos_page +
+					(XP_MAX_PARTITIONS * sizeof(AMO_t)));
+
+
+	(void) xpc_IPI_send(&amos[w_index], (1UL << b_index), to_nasid,
+				to_phys_cpuid, SGI_XPC_ACTIVATE);
+}
+
+static inline void
+xpc_IPI_send_activate(struct xpc_vars *vars)
+{
+	xpc_activate_IRQ_send(vars->amos_page_pa, cnodeid_to_nasid(0),
+				vars->act_nasid, vars->act_phys_cpuid);
+}
+
+static inline void
+xpc_IPI_send_activated(struct xpc_partition *part)
+{
+	xpc_activate_IRQ_send(part->remote_amos_page_pa, cnodeid_to_nasid(0),
+			part->remote_act_nasid, part->remote_act_phys_cpuid);
+}
+
+static inline void
+xpc_IPI_send_reactivate(struct xpc_partition *part)
+{
+	xpc_activate_IRQ_send(xpc_vars->amos_page_pa, part->reactivate_nasid,
+				xpc_vars->act_nasid, xpc_vars->act_phys_cpuid);
+}
+
+
+/*
+ * IPIs associated with SGI_XPC_NOTIFY IRQ.
+ */
+
+/*
+ * Send an IPI to the remote partition that is associated with the
+ * specified channel.
+ */
+#define XPC_NOTIFY_IRQ_SEND(_ch, _ipi_f, _irq_f) \
+		xpc_notify_IRQ_send(_ch, _ipi_f, #_ipi_f, _irq_f)
+
+static inline void
+xpc_notify_IRQ_send(struct xpc_channel *ch, u8 ipi_flag, char *ipi_flag_string,
+			unsigned long *irq_flags)
+{
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
+	enum xpc_retval ret;
+
+
+	if (likely(part->act_state != XPC_P_DEACTIVATING)) {
+		ret = xpc_IPI_send(part->remote_IPI_amo_va,
+					(u64) ipi_flag << (ch->number * 8),
+					part->remote_IPI_nasid,
+					part->remote_IPI_phys_cpuid,
+					SGI_XPC_NOTIFY);
+		dev_dbg(xpc_chan, "%s sent to partid=%d, channel=%d, ret=%d\n",
+			ipi_flag_string, ch->partid, ch->number, ret);
+		if (unlikely(ret != xpcSuccess)) {
+			if (irq_flags != NULL) {
+				spin_unlock_irqrestore(&ch->lock, *irq_flags);
+			}
+			XPC_DEACTIVATE_PARTITION(part, ret);
+			if (irq_flags != NULL) {
+				spin_lock_irqsave(&ch->lock, *irq_flags);
+			}
+		}
+	}
+}
+
+
+/*
+ * Make it look like the remote partition, which is associated with the
+ * specified channel, sent us an IPI. This faked IPI will be handled
+ * by xpc_dropped_IPI_check().
+ */
+#define XPC_NOTIFY_IRQ_SEND_LOCAL(_ch, _ipi_f) \
+		xpc_notify_IRQ_send_local(_ch, _ipi_f, #_ipi_f)
+
+static inline void
+xpc_notify_IRQ_send_local(struct xpc_channel *ch, u8 ipi_flag,
+				char *ipi_flag_string)
+{
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
+
+
+	FETCHOP_STORE_OP(TO_AMO((u64) &part->local_IPI_amo_va->variable),
+			FETCHOP_OR, ((u64) ipi_flag << (ch->number * 8)));
+	dev_dbg(xpc_chan, "%s sent local from partid=%d, channel=%d\n",
+		ipi_flag_string, ch->partid, ch->number);
+}
+
+
+/*
+ * The sending and receiving of IPIs includes the setting of an AMO variable
+ * to indicate the reason the IPI was sent. The 64-bit variable is divided
+ * up into eight bytes, ordered from right to left. Byte zero pertains to
+ * channel 0, byte one to channel 1, and so on. Each byte is described by
+ * the following IPI flags.
+ */
+
+#define	XPC_IPI_CLOSEREQUEST	0x01
+#define	XPC_IPI_CLOSEREPLY	0x02
+#define	XPC_IPI_OPENREQUEST	0x04
+#define	XPC_IPI_OPENREPLY	0x08
+#define	XPC_IPI_MSGREQUEST	0x10
+
+
+/* given an AMO variable and a channel#, get its associated IPI flags */
+#define XPC_GET_IPI_FLAGS(_amo, _c)	((u8) (((_amo) >> ((_c) * 8)) & 0xff))
+
+#define	XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(_amo) ((_amo) & 0x0f0f0f0f0f0f0f0f)
+#define XPC_ANY_MSG_IPI_FLAGS_SET(_amo)       ((_amo) & 0x1010101010101010)
+
+
+static inline void
+xpc_IPI_send_closerequest(struct xpc_channel *ch, unsigned long *irq_flags)
+{
+	struct xpc_openclose_args *args = ch->local_openclose_args;
+
+
+	args->reason = ch->reason;
+
+	XPC_NOTIFY_IRQ_SEND(ch, XPC_IPI_CLOSEREQUEST, irq_flags);
+}
+
+static inline void
+xpc_IPI_send_closereply(struct xpc_channel *ch, unsigned long *irq_flags)
+{
+	XPC_NOTIFY_IRQ_SEND(ch, XPC_IPI_CLOSEREPLY, irq_flags);
+}
+
+static inline void
+xpc_IPI_send_openrequest(struct xpc_channel *ch, unsigned long *irq_flags)
+{
+	struct xpc_openclose_args *args = ch->local_openclose_args;
+
+
+	args->msg_size = ch->msg_size;
+	args->local_nentries = ch->local_nentries;
+
+	XPC_NOTIFY_IRQ_SEND(ch, XPC_IPI_OPENREQUEST, irq_flags);
+}
+
+static inline void
+xpc_IPI_send_openreply(struct xpc_channel *ch, unsigned long *irq_flags)
+{
+	struct xpc_openclose_args *args = ch->local_openclose_args;
+
+
+	args->remote_nentries = ch->remote_nentries;
+	args->local_nentries = ch->local_nentries;
+	args->local_msgqueue_pa = __pa(ch->local_msgqueue);
+
+	XPC_NOTIFY_IRQ_SEND(ch, XPC_IPI_OPENREPLY, irq_flags);
+}
+
+static inline void
+xpc_IPI_send_msgrequest(struct xpc_channel *ch)
+{
+	XPC_NOTIFY_IRQ_SEND(ch, XPC_IPI_MSGREQUEST, NULL);
+}
+
+static inline void
+xpc_IPI_send_local_msgrequest(struct xpc_channel *ch)
+{
+	XPC_NOTIFY_IRQ_SEND_LOCAL(ch, XPC_IPI_MSGREQUEST);
+}
+
+
+/*
+ * Memory for XPC's AMO variables is allocated by the MSPEC driver. These
+ * pages are located in the lowest granule. The lowest granule uses 4k pages
+ * for cached references and an alternate TLB handler to never provide a
+ * cacheable mapping for the entire region. This will prevent speculative
+ * reading of cached copies of our lines from being issued which will cause
+ * a PI FSB Protocol error to be generated by the SHUB. For XPC, we need 64
+ * (XP_MAX_PARTITIONS) AMO variables for message notification (xpc_main.c)
+ * and an additional 16 AMO variables for partition activation (xpc_hb.c).
+ */
+static inline AMO_t *
+xpc_IPI_init(partid_t partid)
+{
+	AMO_t *part_amo = xpc_vars->amos_page + partid;
+
+
+	xpc_IPI_receive(part_amo);
+	return part_amo;
+}
+
+
+
+static inline enum xpc_retval
+xpc_map_bte_errors(bte_result_t error)
+{
+	switch (error) {
+	case BTE_SUCCESS:	return xpcSuccess;
+	case BTEFAIL_DIR:	return xpcBteDirectoryError;
+	case BTEFAIL_POISON:	return xpcBtePoisonError;
+	case BTEFAIL_WERR:	return xpcBteWriteError;
+	case BTEFAIL_ACCESS:	return xpcBteAccessError;
+	case BTEFAIL_PWERR:	return xpcBtePWriteError;
+	case BTEFAIL_PRERR:	return xpcBtePReadError;
+	case BTEFAIL_TOUT:	return xpcBteTimeOutError;
+	case BTEFAIL_XTERR:	return xpcBteXtalkError;
+	case BTEFAIL_NOTAVAIL:	return xpcBteNotAvailable;
+	default:		return xpcBteUnmappedError;
+	}
+}
+
+
+
+static inline void *
+xpc_kmalloc_cacheline_aligned(size_t size, int flags, void **base)
+{
+	/* see if kmalloc will give us cachline aligned memory by default */
+	*base = kmalloc(size, flags);
+	if (*base == NULL) {
+		return NULL;
+	}
+	if ((u64) *base == L1_CACHE_ALIGN((u64) *base)) {
+		return *base;
+	}
+	kfree(*base);
+
+	/* nope, we'll have to do it ourselves */
+	*base = kmalloc(size + L1_CACHE_BYTES, flags);
+	if (*base == NULL) {
+		return NULL;
+	}
+	return (void *) L1_CACHE_ALIGN((u64) *base);
+}
+
+
+/*
+ * Check to see if there is any channel activity to/from the specified
+ * partition.
+ */
+static inline void
+xpc_check_for_channel_activity(struct xpc_partition *part)
+{
+	u64 IPI_amo;
+	unsigned long irq_flags;
+
+
+	IPI_amo = xpc_IPI_receive(part->local_IPI_amo_va);
+	if (IPI_amo == 0) {
+		return;
+	}
+
+	spin_lock_irqsave(&part->IPI_lock, irq_flags);
+	part->local_IPI_amo |= IPI_amo;
+	spin_unlock_irqrestore(&part->IPI_lock, irq_flags);
+
+	dev_dbg(xpc_chan, "received IPI from partid=%d, IPI_amo=0x%lx\n",
+		XPC_PARTID(part), IPI_amo);
+
+	xpc_wakeup_channel_mgr(part);
+}
+
+
+#endif /* _IA64_SN_KERNEL_XPC_H */
+

arch/ia64/sn/kernel/xpc_channel.c

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2004-2005 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+
+
+/*
+ * Cross Partition Communication (XPC) channel support.
+ *
+ *	This is the part of XPC that manages the channels and
+ *	sends/receives messages across them to/from other partitions.
+ *
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/cache.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <asm/sn/bte.h>
+#include <asm/sn/sn_sal.h>
+#include "xpc.h"
+
+
+/*
+ * Set up the initial values for the XPartition Communication channels.
+ */
+static void
+xpc_initialize_channels(struct xpc_partition *part, partid_t partid)
+{
+	int ch_number;
+	struct xpc_channel *ch;
+
+
+	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
+		ch = &part->channels[ch_number];
+
+		ch->partid = partid;
+		ch->number = ch_number;
+		ch->flags = XPC_C_DISCONNECTED;
+
+		ch->local_GP = &part->local_GPs[ch_number];
+		ch->local_openclose_args =
+					&part->local_openclose_args[ch_number];
+
+		atomic_set(&ch->kthreads_assigned, 0);
+		atomic_set(&ch->kthreads_idle, 0);
+		atomic_set(&ch->kthreads_active, 0);
+
+		atomic_set(&ch->references, 0);
+		atomic_set(&ch->n_to_notify, 0);
+
+		spin_lock_init(&ch->lock);
+		sema_init(&ch->msg_to_pull_sema, 1);	/* mutex */
+
+		atomic_set(&ch->n_on_msg_allocate_wq, 0);
+		init_waitqueue_head(&ch->msg_allocate_wq);
+		init_waitqueue_head(&ch->idle_wq);
+	}
+}
+
+
+/*
+ * Setup the infrastructure necessary to support XPartition Communication
+ * between the specified remote partition and the local one.
+ */
+enum xpc_retval
+xpc_setup_infrastructure(struct xpc_partition *part)
+{
+	int ret;
+	struct timer_list *timer;
+	partid_t partid = XPC_PARTID(part);
+
+
+	/*
+	 * Zero out MOST of the entry for this partition. Only the fields
+	 * starting with `nchannels' will be zeroed. The preceding fields must
+	 * remain `viable' across partition ups and downs, since they may be
+	 * referenced during this memset() operation.
+	 */
+	memset(&part->nchannels, 0, sizeof(struct xpc_partition) -
+				offsetof(struct xpc_partition, nchannels));
+
+	/*
+	 * Allocate all of the channel structures as a contiguous chunk of
+	 * memory.
+	 */
+	part->channels = kmalloc(sizeof(struct xpc_channel) * XPC_NCHANNELS,
+								GFP_KERNEL);
+	if (part->channels == NULL) {
+		dev_err(xpc_chan, "can't get memory for channels\n");
+		return xpcNoMemory;
+	}
+	memset(part->channels, 0, sizeof(struct xpc_channel) * XPC_NCHANNELS);
+
+	part->nchannels = XPC_NCHANNELS;
+
+
+	/* allocate all the required GET/PUT values */
+
+	part->local_GPs = xpc_kmalloc_cacheline_aligned(XPC_GP_SIZE,
+					GFP_KERNEL, &part->local_GPs_base);
+	if (part->local_GPs == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		dev_err(xpc_chan, "can't get memory for local get/put "
+			"values\n");
+		return xpcNoMemory;
+	}
+	memset(part->local_GPs, 0, XPC_GP_SIZE);
+
+	part->remote_GPs = xpc_kmalloc_cacheline_aligned(XPC_GP_SIZE,
+					GFP_KERNEL, &part->remote_GPs_base);
+	if (part->remote_GPs == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		dev_err(xpc_chan, "can't get memory for remote get/put "
+			"values\n");
+		return xpcNoMemory;
+	}
+	memset(part->remote_GPs, 0, XPC_GP_SIZE);
+
+
+	/* allocate all the required open and close args */
+
+	part->local_openclose_args = xpc_kmalloc_cacheline_aligned(
+					XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
+					&part->local_openclose_args_base);
+	if (part->local_openclose_args == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		kfree(part->remote_GPs_base);
+		part->remote_GPs = NULL;
+		dev_err(xpc_chan, "can't get memory for local connect args\n");
+		return xpcNoMemory;
+	}
+	memset(part->local_openclose_args, 0, XPC_OPENCLOSE_ARGS_SIZE);
+
+	part->remote_openclose_args = xpc_kmalloc_cacheline_aligned(
+					XPC_OPENCLOSE_ARGS_SIZE, GFP_KERNEL,
+					&part->remote_openclose_args_base);
+	if (part->remote_openclose_args == NULL) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		kfree(part->remote_GPs_base);
+		part->remote_GPs = NULL;
+		kfree(part->local_openclose_args_base);
+		part->local_openclose_args = NULL;
+		dev_err(xpc_chan, "can't get memory for remote connect args\n");
+		return xpcNoMemory;
+	}
+	memset(part->remote_openclose_args, 0, XPC_OPENCLOSE_ARGS_SIZE);
+
+
+	xpc_initialize_channels(part, partid);
+
+	atomic_set(&part->nchannels_active, 0);
+
+
+	/* local_IPI_amo were set to 0 by an earlier memset() */
+
+	/* Initialize this partitions AMO_t structure */
+	part->local_IPI_amo_va = xpc_IPI_init(partid);
+
+	spin_lock_init(&part->IPI_lock);
+
+	atomic_set(&part->channel_mgr_requests, 1);
+	init_waitqueue_head(&part->channel_mgr_wq);
+
+	sprintf(part->IPI_owner, "xpc%02d", partid);
+	ret = request_irq(SGI_XPC_NOTIFY, xpc_notify_IRQ_handler, SA_SHIRQ,
+				part->IPI_owner, (void *) (u64) partid);
+	if (ret != 0) {
+		kfree(part->channels);
+		part->channels = NULL;
+		kfree(part->local_GPs_base);
+		part->local_GPs = NULL;
+		kfree(part->remote_GPs_base);
+		part->remote_GPs = NULL;
+		kfree(part->local_openclose_args_base);
+		part->local_openclose_args = NULL;
+		kfree(part->remote_openclose_args_base);
+		part->remote_openclose_args = NULL;
+		dev_err(xpc_chan, "can't register NOTIFY IRQ handler, "
+			"errno=%d\n", -ret);
+		return xpcLackOfResources;
+	}
+
+	/* Setup a timer to check for dropped IPIs */
+	timer = &part->dropped_IPI_timer;
+	init_timer(timer);
+	timer->function = (void (*)(unsigned long)) xpc_dropped_IPI_check;
+	timer->data = (unsigned long) part;
+	timer->expires = jiffies + XPC_P_DROPPED_IPI_WAIT;
+	add_timer(timer);
+
+	/*
+	 * With the setting of the partition setup_state to XPC_P_SETUP, we're
+	 * declaring that this partition is ready to go.
+	 */
+	(volatile u8) part->setup_state = XPC_P_SETUP;
+
+
+	/*
+	 * Setup the per partition specific variables required by the
+	 * remote partition to establish channel connections with us.
+	 *
+	 * The setting of the magic # indicates that these per partition
+	 * specific variables are ready to be used.
+	 */
+	xpc_vars_part[partid].GPs_pa = __pa(part->local_GPs);
+	xpc_vars_part[partid].openclose_args_pa =
+					__pa(part->local_openclose_args);
+	xpc_vars_part[partid].IPI_amo_pa = __pa(part->local_IPI_amo_va);
+	xpc_vars_part[partid].IPI_nasid = cpuid_to_nasid(smp_processor_id());
+	xpc_vars_part[partid].IPI_phys_cpuid =
+					cpu_physical_id(smp_processor_id());
+	xpc_vars_part[partid].nchannels = part->nchannels;
+	(volatile u64) xpc_vars_part[partid].magic = XPC_VP_MAGIC1;
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Create a wrapper that hides the underlying mechanism for pulling a cacheline
+ * (or multiple cachelines) from a remote partition.
+ *
+ * src must be a cacheline aligned physical address on the remote partition.
+ * dst must be a cacheline aligned virtual address on this partition.
+ * cnt must be an cacheline sized
+ */
+static enum xpc_retval
+xpc_pull_remote_cachelines(struct xpc_partition *part, void *dst,
+				const void *src, size_t cnt)
+{
+	bte_result_t bte_ret;
+
+
+	DBUG_ON((u64) src != L1_CACHE_ALIGN((u64) src));
+	DBUG_ON((u64) dst != L1_CACHE_ALIGN((u64) dst));
+	DBUG_ON(cnt != L1_CACHE_ALIGN(cnt));
+
+	if (part->act_state == XPC_P_DEACTIVATING) {
+		return part->reason;
+	}
+
+	bte_ret = xp_bte_copy((u64) src, (u64) ia64_tpa((u64) dst),
+				(u64) cnt, (BTE_NORMAL | BTE_WACQUIRE), NULL);
+	if (bte_ret == BTE_SUCCESS) {
+		return xpcSuccess;
+	}
+
+	dev_dbg(xpc_chan, "xp_bte_copy() from partition %d failed, ret=%d\n",
+		XPC_PARTID(part), bte_ret);
+
+	return xpc_map_bte_errors(bte_ret);
+}
+
+
+/*
+ * Pull the remote per partititon specific variables from the specified
+ * partition.
+ */
+enum xpc_retval
+xpc_pull_remote_vars_part(struct xpc_partition *part)
+{
+	u8 buffer[L1_CACHE_BYTES * 2];
+	struct xpc_vars_part *pulled_entry_cacheline =
+			(struct xpc_vars_part *) L1_CACHE_ALIGN((u64) buffer);
+	struct xpc_vars_part *pulled_entry;
+	u64 remote_entry_cacheline_pa, remote_entry_pa;
+	partid_t partid = XPC_PARTID(part);
+	enum xpc_retval ret;
+
+
+	/* pull the cacheline that contains the variables we're interested in */
+
+	DBUG_ON(part->remote_vars_part_pa !=
+				L1_CACHE_ALIGN(part->remote_vars_part_pa));
+	DBUG_ON(sizeof(struct xpc_vars_part) != L1_CACHE_BYTES / 2);
+
+	remote_entry_pa = part->remote_vars_part_pa +
+			sn_partition_id * sizeof(struct xpc_vars_part);
+
+	remote_entry_cacheline_pa = (remote_entry_pa & ~(L1_CACHE_BYTES - 1));
+
+	pulled_entry = (struct xpc_vars_part *) ((u64) pulled_entry_cacheline +
+				(remote_entry_pa & (L1_CACHE_BYTES - 1)));
+
+	ret = xpc_pull_remote_cachelines(part, pulled_entry_cacheline,
+					(void *) remote_entry_cacheline_pa,
+					L1_CACHE_BYTES);
+	if (ret != xpcSuccess) {
+		dev_dbg(xpc_chan, "failed to pull XPC vars_part from "
+			"partition %d, ret=%d\n", partid, ret);
+		return ret;
+	}
+
+
+	/* see if they've been set up yet */
+
+	if (pulled_entry->magic != XPC_VP_MAGIC1 &&
+				pulled_entry->magic != XPC_VP_MAGIC2) {
+
+		if (pulled_entry->magic != 0) {
+			dev_dbg(xpc_chan, "partition %d's XPC vars_part for "
+				"partition %d has bad magic value (=0x%lx)\n",
+				partid, sn_partition_id, pulled_entry->magic);
+			return xpcBadMagic;
+		}
+
+		/* they've not been initialized yet */
+		return xpcRetry;
+	}
+
+	if (xpc_vars_part[partid].magic == XPC_VP_MAGIC1) {
+
+		/* validate the variables */
+
+		if (pulled_entry->GPs_pa == 0 ||
+				pulled_entry->openclose_args_pa == 0 ||
+					pulled_entry->IPI_amo_pa == 0) {
+
+			dev_err(xpc_chan, "partition %d's XPC vars_part for "
+				"partition %d are not valid\n", partid,
+				sn_partition_id);
+			return xpcInvalidAddress;
+		}
+
+		/* the variables we imported look to be valid */
+
+		part->remote_GPs_pa = pulled_entry->GPs_pa;
+		part->remote_openclose_args_pa =
+					pulled_entry->openclose_args_pa;
+		part->remote_IPI_amo_va =
+				      (AMO_t *) __va(pulled_entry->IPI_amo_pa);
+		part->remote_IPI_nasid = pulled_entry->IPI_nasid;
+		part->remote_IPI_phys_cpuid = pulled_entry->IPI_phys_cpuid;
+
+		if (part->nchannels > pulled_entry->nchannels) {
+			part->nchannels = pulled_entry->nchannels;
+		}
+
+		/* let the other side know that we've pulled their variables */
+
+		(volatile u64) xpc_vars_part[partid].magic = XPC_VP_MAGIC2;
+	}
+
+	if (pulled_entry->magic == XPC_VP_MAGIC1) {
+		return xpcRetry;
+	}
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Get the IPI flags and pull the openclose args and/or remote GPs as needed.
+ */
+static u64
+xpc_get_IPI_flags(struct xpc_partition *part)
+{
+	unsigned long irq_flags;
+	u64 IPI_amo;
+	enum xpc_retval ret;
+
+
+	/*
+	 * See if there are any IPI flags to be handled.
+	 */
+
+	spin_lock_irqsave(&part->IPI_lock, irq_flags);
+	if ((IPI_amo = part->local_IPI_amo) != 0) {
+		part->local_IPI_amo = 0;
+	}
+	spin_unlock_irqrestore(&part->IPI_lock, irq_flags);
+
+
+	if (XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(IPI_amo)) {
+		ret = xpc_pull_remote_cachelines(part,
+					part->remote_openclose_args,
+					(void *) part->remote_openclose_args_pa,
+					XPC_OPENCLOSE_ARGS_SIZE);
+		if (ret != xpcSuccess) {
+			XPC_DEACTIVATE_PARTITION(part, ret);
+
+			dev_dbg(xpc_chan, "failed to pull openclose args from "
+				"partition %d, ret=%d\n", XPC_PARTID(part),
+				ret);
+
+			/* don't bother processing IPIs anymore */
+			IPI_amo = 0;
+		}
+	}
+
+	if (XPC_ANY_MSG_IPI_FLAGS_SET(IPI_amo)) {
+		ret = xpc_pull_remote_cachelines(part, part->remote_GPs,
+						(void *) part->remote_GPs_pa,
+						XPC_GP_SIZE);
+		if (ret != xpcSuccess) {
+			XPC_DEACTIVATE_PARTITION(part, ret);
+
+			dev_dbg(xpc_chan, "failed to pull GPs from partition "
+				"%d, ret=%d\n", XPC_PARTID(part), ret);
+
+			/* don't bother processing IPIs anymore */
+			IPI_amo = 0;
+		}
+	}
+
+	return IPI_amo;
+}
+
+
+/*
+ * Allocate the local message queue and the notify queue.
+ */
+static enum xpc_retval
+xpc_allocate_local_msgqueue(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	int nentries;
+	size_t nbytes;
+
+
+	// >>> may want to check for ch->flags & XPC_C_DISCONNECTING between
+	// >>> iterations of the for-loop, bail if set?
+
+	// >>> should we impose a minumum #of entries? like 4 or 8?
+	for (nentries = ch->local_nentries; nentries > 0; nentries--) {
+
+		nbytes = nentries * ch->msg_size;
+		ch->local_msgqueue = xpc_kmalloc_cacheline_aligned(nbytes,
+						(GFP_KERNEL | GFP_DMA),
+						&ch->local_msgqueue_base);
+		if (ch->local_msgqueue == NULL) {
+			continue;
+		}
+		memset(ch->local_msgqueue, 0, nbytes);
+
+		nbytes = nentries * sizeof(struct xpc_notify);
+		ch->notify_queue = kmalloc(nbytes, (GFP_KERNEL | GFP_DMA));
+		if (ch->notify_queue == NULL) {
+			kfree(ch->local_msgqueue_base);
+			ch->local_msgqueue = NULL;
+			continue;
+		}
+		memset(ch->notify_queue, 0, nbytes);
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		if (nentries < ch->local_nentries) {
+			dev_dbg(xpc_chan, "nentries=%d local_nentries=%d, "
+				"partid=%d, channel=%d\n", nentries,
+				ch->local_nentries, ch->partid, ch->number);
+
+			ch->local_nentries = nentries;
+		}
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		return xpcSuccess;
+	}
+
+	dev_dbg(xpc_chan, "can't get memory for local message queue and notify "
+		"queue, partid=%d, channel=%d\n", ch->partid, ch->number);
+	return xpcNoMemory;
+}
+
+
+/*
+ * Allocate the cached remote message queue.
+ */
+static enum xpc_retval
+xpc_allocate_remote_msgqueue(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	int nentries;
+	size_t nbytes;
+
+
+	DBUG_ON(ch->remote_nentries <= 0);
+
+	// >>> may want to check for ch->flags & XPC_C_DISCONNECTING between
+	// >>> iterations of the for-loop, bail if set?
+
+	// >>> should we impose a minumum #of entries? like 4 or 8?
+	for (nentries = ch->remote_nentries; nentries > 0; nentries--) {
+
+		nbytes = nentries * ch->msg_size;
+		ch->remote_msgqueue = xpc_kmalloc_cacheline_aligned(nbytes,
+						(GFP_KERNEL | GFP_DMA),
+						&ch->remote_msgqueue_base);
+		if (ch->remote_msgqueue == NULL) {
+			continue;
+		}
+		memset(ch->remote_msgqueue, 0, nbytes);
+
+		spin_lock_irqsave(&ch->lock, irq_flags);
+		if (nentries < ch->remote_nentries) {
+			dev_dbg(xpc_chan, "nentries=%d remote_nentries=%d, "
+				"partid=%d, channel=%d\n", nentries,
+				ch->remote_nentries, ch->partid, ch->number);
+
+			ch->remote_nentries = nentries;
+		}
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		return xpcSuccess;
+	}
+
+	dev_dbg(xpc_chan, "can't get memory for cached remote message queue, "
+		"partid=%d, channel=%d\n", ch->partid, ch->number);
+	return xpcNoMemory;
+}
+
+
+/*
+ * Allocate message queues and other stuff associated with a channel.
+ *
+ * Note: Assumes all of the channel sizes are filled in.
+ */
+static enum xpc_retval
+xpc_allocate_msgqueues(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	int i;
+	enum xpc_retval ret;
+
+
+	DBUG_ON(ch->flags & XPC_C_SETUP);
+
+	if ((ret = xpc_allocate_local_msgqueue(ch)) != xpcSuccess) {
+		return ret;
+	}
+
+	if ((ret = xpc_allocate_remote_msgqueue(ch)) != xpcSuccess) {
+		kfree(ch->local_msgqueue_base);
+		ch->local_msgqueue = NULL;
+		kfree(ch->notify_queue);
+		ch->notify_queue = NULL;
+		return ret;
+	}
+
+	for (i = 0; i < ch->local_nentries; i++) {
+		/* use a semaphore as an event wait queue */
+		sema_init(&ch->notify_queue[i].sema, 0);
+	}
+
+	sema_init(&ch->teardown_sema, 0);	/* event wait */
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+	ch->flags |= XPC_C_SETUP;
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Process a connect message from a remote partition.
+ *
+ * Note: xpc_process_connect() is expecting to be called with the
+ * spin_lock_irqsave held and will leave it locked upon return.
+ */
+static void
+xpc_process_connect(struct xpc_channel *ch, unsigned long *irq_flags)
+{
+	enum xpc_retval ret;
+
+
+	DBUG_ON(!spin_is_locked(&ch->lock));
+
+	if (!(ch->flags & XPC_C_OPENREQUEST) ||
+				!(ch->flags & XPC_C_ROPENREQUEST)) {
+		/* nothing more to do for now */
+		return;
+	}
+	DBUG_ON(!(ch->flags & XPC_C_CONNECTING));
+
+	if (!(ch->flags & XPC_C_SETUP)) {
+		spin_unlock_irqrestore(&ch->lock, *irq_flags);
+		ret = xpc_allocate_msgqueues(ch);
+		spin_lock_irqsave(&ch->lock, *irq_flags);
+
+		if (ret != xpcSuccess) {
+			XPC_DISCONNECT_CHANNEL(ch, ret, irq_flags);
+		}
+		if (ch->flags & (XPC_C_CONNECTED | XPC_C_DISCONNECTING)) {
+			return;
+		}
+
+		DBUG_ON(!(ch->flags & XPC_C_SETUP));
+		DBUG_ON(ch->local_msgqueue == NULL);
+		DBUG_ON(ch->remote_msgqueue == NULL);
+	}
+
+	if (!(ch->flags & XPC_C_OPENREPLY)) {
+		ch->flags |= XPC_C_OPENREPLY;
+		xpc_IPI_send_openreply(ch, irq_flags);
+	}
+
+	if (!(ch->flags & XPC_C_ROPENREPLY)) {
+		return;
+	}
+
+	DBUG_ON(ch->remote_msgqueue_pa == 0);
+
+	ch->flags = (XPC_C_CONNECTED | XPC_C_SETUP);	/* clear all else */
+
+	dev_info(xpc_chan, "channel %d to partition %d connected\n",
+		ch->number, ch->partid);
+
+	spin_unlock_irqrestore(&ch->lock, *irq_flags);
+	xpc_create_kthreads(ch, 1);
+	spin_lock_irqsave(&ch->lock, *irq_flags);
+}
+
+
+/*
+ * Free up message queues and other stuff that were allocated for the specified
+ * channel.
+ *
+ * Note: ch->reason and ch->reason_line are left set for debugging purposes,
+ * they're cleared when XPC_C_DISCONNECTED is cleared.
+ */
+static void
+xpc_free_msgqueues(struct xpc_channel *ch)
+{
+	DBUG_ON(!spin_is_locked(&ch->lock));
+	DBUG_ON(atomic_read(&ch->n_to_notify) != 0);
+
+	ch->remote_msgqueue_pa = 0;
+	ch->func = NULL;
+	ch->key = NULL;
+	ch->msg_size = 0;
+	ch->local_nentries = 0;
+	ch->remote_nentries = 0;
+	ch->kthreads_assigned_limit = 0;
+	ch->kthreads_idle_limit = 0;
+
+	ch->local_GP->get = 0;
+	ch->local_GP->put = 0;
+	ch->remote_GP.get = 0;
+	ch->remote_GP.put = 0;
+	ch->w_local_GP.get = 0;
+	ch->w_local_GP.put = 0;
+	ch->w_remote_GP.get = 0;
+	ch->w_remote_GP.put = 0;
+	ch->next_msg_to_pull = 0;
+
+	if (ch->flags & XPC_C_SETUP) {
+		ch->flags &= ~XPC_C_SETUP;
+
+		dev_dbg(xpc_chan, "ch->flags=0x%x, partid=%d, channel=%d\n",
+			ch->flags, ch->partid, ch->number);
+
+		kfree(ch->local_msgqueue_base);
+		ch->local_msgqueue = NULL;
+		kfree(ch->remote_msgqueue_base);
+		ch->remote_msgqueue = NULL;
+		kfree(ch->notify_queue);
+		ch->notify_queue = NULL;
+
+		/* in case someone is waiting for the teardown to complete */
+		up(&ch->teardown_sema);
+	}
+}
+
+
+/*
+ * spin_lock_irqsave() is expected to be held on entry.
+ */
+static void
+xpc_process_disconnect(struct xpc_channel *ch, unsigned long *irq_flags)
+{
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
+	u32 ch_flags = ch->flags;
+
+
+	DBUG_ON(!spin_is_locked(&ch->lock));
+
+	if (!(ch->flags & XPC_C_DISCONNECTING)) {
+		return;
+	}
+
+	DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));
+
+	/* make sure all activity has settled down first */
+
+	if (atomic_read(&ch->references) > 0) {
+		return;
+	}
+	DBUG_ON(atomic_read(&ch->kthreads_assigned) != 0);
+
+	/* it's now safe to free the channel's message queues */
+
+	xpc_free_msgqueues(ch);
+	DBUG_ON(ch->flags & XPC_C_SETUP);
+
+	if (part->act_state != XPC_P_DEACTIVATING) {
+
+		/* as long as the other side is up do the full protocol */
+
+		if (!(ch->flags & XPC_C_RCLOSEREQUEST)) {
+			return;
+		}
+
+		if (!(ch->flags & XPC_C_CLOSEREPLY)) {
+			ch->flags |= XPC_C_CLOSEREPLY;
+			xpc_IPI_send_closereply(ch, irq_flags);
+		}
+
+		if (!(ch->flags & XPC_C_RCLOSEREPLY)) {
+			return;
+		}
+	}
+
+	/* both sides are disconnected now */
+
+	ch->flags = XPC_C_DISCONNECTED;	/* clear all flags, but this one */
+
+	atomic_dec(&part->nchannels_active);
+
+	if (ch_flags & XPC_C_WASCONNECTED) {
+		dev_info(xpc_chan, "channel %d to partition %d disconnected, "
+			"reason=%d\n", ch->number, ch->partid, ch->reason);
+	}
+}
+
+
+/*
+ * Process a change in the channel's remote connection state.
+ */
+static void
+xpc_process_openclose_IPI(struct xpc_partition *part, int ch_number,
+				u8 IPI_flags)
+{
+	unsigned long irq_flags;
+	struct xpc_openclose_args *args =
+				&part->remote_openclose_args[ch_number];
+	struct xpc_channel *ch = &part->channels[ch_number];
+	enum xpc_retval reason;
+
+
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+
+
+	if (IPI_flags & XPC_IPI_CLOSEREQUEST) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_CLOSEREQUEST (reason=%d) received "
+			"from partid=%d, channel=%d\n", args->reason,
+			ch->partid, ch->number);
+
+		/*
+		 * If RCLOSEREQUEST is set, we're probably waiting for
+		 * RCLOSEREPLY. We should find it and a ROPENREQUEST packed
+		 * with this RCLOSEQREUQEST in the IPI_flags.
+		 */
+
+		if (ch->flags & XPC_C_RCLOSEREQUEST) {
+			DBUG_ON(!(ch->flags & XPC_C_DISCONNECTING));
+			DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));
+			DBUG_ON(!(ch->flags & XPC_C_CLOSEREPLY));
+			DBUG_ON(ch->flags & XPC_C_RCLOSEREPLY);
+
+			DBUG_ON(!(IPI_flags & XPC_IPI_CLOSEREPLY));
+			IPI_flags &= ~XPC_IPI_CLOSEREPLY;
+			ch->flags |= XPC_C_RCLOSEREPLY;
+
+			/* both sides have finished disconnecting */
+			xpc_process_disconnect(ch, &irq_flags);
+		}
+
+		if (ch->flags & XPC_C_DISCONNECTED) {
+			// >>> explain this section
+
+			if (!(IPI_flags & XPC_IPI_OPENREQUEST)) {
+				DBUG_ON(part->act_state !=
+							XPC_P_DEACTIVATING);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+				return;
+			}
+
+			XPC_SET_REASON(ch, 0, 0);
+			ch->flags &= ~XPC_C_DISCONNECTED;
+
+			atomic_inc(&part->nchannels_active);
+			ch->flags |= (XPC_C_CONNECTING | XPC_C_ROPENREQUEST);
+		}
+
+		IPI_flags &= ~(XPC_IPI_OPENREQUEST | XPC_IPI_OPENREPLY);
+
+		/*
+		 * The meaningful CLOSEREQUEST connection state fields are:
+		 *      reason = reason connection is to be closed
+		 */
+
+		ch->flags |= XPC_C_RCLOSEREQUEST;
+
+		if (!(ch->flags & XPC_C_DISCONNECTING)) {
+			reason = args->reason;
+			if (reason <= xpcSuccess || reason > xpcUnknownReason) {
+				reason = xpcUnknownReason;
+			} else if (reason == xpcUnregistering) {
+				reason = xpcOtherUnregistering;
+			}
+
+			XPC_DISCONNECT_CHANNEL(ch, reason, &irq_flags);
+		} else {
+			xpc_process_disconnect(ch, &irq_flags);
+		}
+	}
+
+
+	if (IPI_flags & XPC_IPI_CLOSEREPLY) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_CLOSEREPLY received from partid=%d,"
+			" channel=%d\n", ch->partid, ch->number);
+
+		if (ch->flags & XPC_C_DISCONNECTED) {
+			DBUG_ON(part->act_state != XPC_P_DEACTIVATING);
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return;
+		}
+
+		DBUG_ON(!(ch->flags & XPC_C_CLOSEREQUEST));
+		DBUG_ON(!(ch->flags & XPC_C_RCLOSEREQUEST));
+
+		ch->flags |= XPC_C_RCLOSEREPLY;
+
+		if (ch->flags & XPC_C_CLOSEREPLY) {
+			/* both sides have finished disconnecting */
+			xpc_process_disconnect(ch, &irq_flags);
+		}
+	}
+
+
+	if (IPI_flags & XPC_IPI_OPENREQUEST) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_OPENREQUEST (msg_size=%d, "
+			"local_nentries=%d) received from partid=%d, "
+			"channel=%d\n", args->msg_size, args->local_nentries,
+			ch->partid, ch->number);
+
+		if ((ch->flags & XPC_C_DISCONNECTING) ||
+					part->act_state == XPC_P_DEACTIVATING) {
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return;
+		}
+		DBUG_ON(!(ch->flags & (XPC_C_DISCONNECTED |
+							XPC_C_OPENREQUEST)));
+		DBUG_ON(ch->flags & (XPC_C_ROPENREQUEST | XPC_C_ROPENREPLY |
+					XPC_C_OPENREPLY | XPC_C_CONNECTED));
+
+		/*
+		 * The meaningful OPENREQUEST connection state fields are:
+		 *      msg_size = size of channel's messages in bytes
+		 *      local_nentries = remote partition's local_nentries
+		 */
+		DBUG_ON(args->msg_size == 0);
+		DBUG_ON(args->local_nentries == 0);
+
+		ch->flags |= (XPC_C_ROPENREQUEST | XPC_C_CONNECTING);
+		ch->remote_nentries = args->local_nentries;
+
+
+		if (ch->flags & XPC_C_OPENREQUEST) {
+			if (args->msg_size != ch->msg_size) {
+				XPC_DISCONNECT_CHANNEL(ch, xpcUnequalMsgSizes,
+								&irq_flags);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+				return;
+			}
+		} else {
+			ch->msg_size = args->msg_size;
+
+			XPC_SET_REASON(ch, 0, 0);
+			ch->flags &= ~XPC_C_DISCONNECTED;
+
+			atomic_inc(&part->nchannels_active);
+		}
+
+		xpc_process_connect(ch, &irq_flags);
+	}
+
+
+	if (IPI_flags & XPC_IPI_OPENREPLY) {
+
+		dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY (local_msgqueue_pa=0x%lx, "
+			"local_nentries=%d, remote_nentries=%d) received from "
+			"partid=%d, channel=%d\n", args->local_msgqueue_pa,
+			args->local_nentries, args->remote_nentries,
+			ch->partid, ch->number);
+
+		if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_DISCONNECTED)) {
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return;
+		}
+		DBUG_ON(!(ch->flags & XPC_C_OPENREQUEST));
+		DBUG_ON(!(ch->flags & XPC_C_ROPENREQUEST));
+		DBUG_ON(ch->flags & XPC_C_CONNECTED);
+
+		/*
+		 * The meaningful OPENREPLY connection state fields are:
+		 *      local_msgqueue_pa = physical address of remote
+		 *			    partition's local_msgqueue
+		 *      local_nentries = remote partition's local_nentries
+		 *      remote_nentries = remote partition's remote_nentries
+		 */
+		DBUG_ON(args->local_msgqueue_pa == 0);
+		DBUG_ON(args->local_nentries == 0);
+		DBUG_ON(args->remote_nentries == 0);
+
+		ch->flags |= XPC_C_ROPENREPLY;
+		ch->remote_msgqueue_pa = args->local_msgqueue_pa;
+
+		if (args->local_nentries < ch->remote_nentries) {
+			dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY: new "
+				"remote_nentries=%d, old remote_nentries=%d, "
+				"partid=%d, channel=%d\n",
+				args->local_nentries, ch->remote_nentries,
+				ch->partid, ch->number);
+
+			ch->remote_nentries = args->local_nentries;
+		}
+		if (args->remote_nentries < ch->local_nentries) {
+			dev_dbg(xpc_chan, "XPC_IPI_OPENREPLY: new "
+				"local_nentries=%d, old local_nentries=%d, "
+				"partid=%d, channel=%d\n",
+				args->remote_nentries, ch->local_nentries,
+				ch->partid, ch->number);
+
+			ch->local_nentries = args->remote_nentries;
+		}
+
+		xpc_process_connect(ch, &irq_flags);
+	}
+
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+}
+
+
+/*
+ * Attempt to establish a channel connection to a remote partition.
+ */
+static enum xpc_retval
+xpc_connect_channel(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+	struct xpc_registration *registration = &xpc_registrations[ch->number];
+
+
+	if (down_interruptible(&registration->sema) != 0) {
+		return xpcInterrupted;
+	}
+
+	if (!XPC_CHANNEL_REGISTERED(ch->number)) {
+		up(&registration->sema);
+		return xpcUnregistered;
+	}
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+
+	DBUG_ON(ch->flags & XPC_C_CONNECTED);
+	DBUG_ON(ch->flags & XPC_C_OPENREQUEST);
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		up(&registration->sema);
+		return ch->reason;
+	}
+
+
+	/* add info from the channel connect registration to the channel */
+
+	ch->kthreads_assigned_limit = registration->assigned_limit;
+	ch->kthreads_idle_limit = registration->idle_limit;
+	DBUG_ON(atomic_read(&ch->kthreads_assigned) != 0);
+	DBUG_ON(atomic_read(&ch->kthreads_idle) != 0);
+	DBUG_ON(atomic_read(&ch->kthreads_active) != 0);
+
+	ch->func = registration->func;
+	DBUG_ON(registration->func == NULL);
+	ch->key = registration->key;
+
+	ch->local_nentries = registration->nentries;
+
+	if (ch->flags & XPC_C_ROPENREQUEST) {
+		if (registration->msg_size != ch->msg_size) {
+			/* the local and remote sides aren't the same */
+
+			/*
+			 * Because XPC_DISCONNECT_CHANNEL() can block we're
+			 * forced to up the registration sema before we unlock
+			 * the channel lock. But that's okay here because we're
+			 * done with the part that required the registration
+			 * sema. XPC_DISCONNECT_CHANNEL() requires that the
+			 * channel lock be locked and will unlock and relock
+			 * the channel lock as needed.
+			 */
+			up(&registration->sema);
+			XPC_DISCONNECT_CHANNEL(ch, xpcUnequalMsgSizes,
+								&irq_flags);
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			return xpcUnequalMsgSizes;
+		}
+	} else {
+		ch->msg_size = registration->msg_size;
+
+		XPC_SET_REASON(ch, 0, 0);
+		ch->flags &= ~XPC_C_DISCONNECTED;
+
+		atomic_inc(&xpc_partitions[ch->partid].nchannels_active);
+	}
+
+	up(&registration->sema);
+
+
+	/* initiate the connection */
+
+	ch->flags |= (XPC_C_OPENREQUEST | XPC_C_CONNECTING);
+	xpc_IPI_send_openrequest(ch, &irq_flags);
+
+	xpc_process_connect(ch, &irq_flags);
+
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Notify those who wanted to be notified upon delivery of their message.
+ */
+static void
+xpc_notify_senders(struct xpc_channel *ch, enum xpc_retval reason, s64 put)
+{
+	struct xpc_notify *notify;
+	u8 notify_type;
+	s64 get = ch->w_remote_GP.get - 1;
+
+
+	while (++get < put && atomic_read(&ch->n_to_notify) > 0) {
+
+		notify = &ch->notify_queue[get % ch->local_nentries];
+
+		/*
+		 * See if the notify entry indicates it was associated with
+		 * a message who's sender wants to be notified. It is possible
+		 * that it is, but someone else is doing or has done the
+		 * notification.
+		 */
+		notify_type = notify->type;
+		if (notify_type == 0 ||
+				cmpxchg(&notify->type, notify_type, 0) !=
+								notify_type) {
+			continue;
+		}
+
+		DBUG_ON(notify_type != XPC_N_CALL);
+
+		atomic_dec(&ch->n_to_notify);
+
+		if (notify->func != NULL) {
+			dev_dbg(xpc_chan, "notify->func() called, notify=0x%p, "
+				"msg_number=%ld, partid=%d, channel=%d\n",
+				(void *) notify, get, ch->partid, ch->number);
+
+			notify->func(reason, ch->partid, ch->number,
+								notify->key);
+
+			dev_dbg(xpc_chan, "notify->func() returned, "
+				"notify=0x%p, msg_number=%ld, partid=%d, "
+				"channel=%d\n", (void *) notify, get,
+				ch->partid, ch->number);
+		}
+	}
+}
+
+
+/*
+ * Clear some of the msg flags in the local message queue.
+ */
+static inline void
+xpc_clear_local_msgqueue_flags(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg;
+	s64 get;
+
+
+	get = ch->w_remote_GP.get;
+	do {
+		msg = (struct xpc_msg *) ((u64) ch->local_msgqueue +
+				(get % ch->local_nentries) * ch->msg_size);
+		msg->flags = 0;
+	} while (++get < (volatile s64) ch->remote_GP.get);
+}
+
+
+/*
+ * Clear some of the msg flags in the remote message queue.
+ */
+static inline void
+xpc_clear_remote_msgqueue_flags(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg;
+	s64 put;
+
+
+	put = ch->w_remote_GP.put;
+	do {
+		msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue +
+				(put % ch->remote_nentries) * ch->msg_size);
+		msg->flags = 0;
+	} while (++put < (volatile s64) ch->remote_GP.put);
+}
+
+
+static void
+xpc_process_msg_IPI(struct xpc_partition *part, int ch_number)
+{
+	struct xpc_channel *ch = &part->channels[ch_number];
+	int nmsgs_sent;
+
+
+	ch->remote_GP = part->remote_GPs[ch_number];
+
+
+	/* See what, if anything, has changed for each connected channel */
+
+	xpc_msgqueue_ref(ch);
+
+	if (ch->w_remote_GP.get == ch->remote_GP.get &&
+				ch->w_remote_GP.put == ch->remote_GP.put) {
+		/* nothing changed since GPs were last pulled */
+		xpc_msgqueue_deref(ch);
+		return;
+	}
+
+	if (!(ch->flags & XPC_C_CONNECTED)){
+		xpc_msgqueue_deref(ch);
+		return;
+	}
+
+
+	/*
+	 * First check to see if messages recently sent by us have been
+	 * received by the other side. (The remote GET value will have
+	 * changed since we last looked at it.)
+	 */
+
+	if (ch->w_remote_GP.get != ch->remote_GP.get) {
+
+		/*
+		 * We need to notify any senders that want to be notified
+		 * that their sent messages have been received by their
+		 * intended recipients. We need to do this before updating
+		 * w_remote_GP.get so that we don't allocate the same message
+		 * queue entries prematurely (see xpc_allocate_msg()).
+		 */
+		if (atomic_read(&ch->n_to_notify) > 0) {
+			/*
+			 * Notify senders that messages sent have been
+			 * received and delivered by the other side.
+			 */
+			xpc_notify_senders(ch, xpcMsgDelivered,
+							ch->remote_GP.get);
+		}
+
+		/*
+		 * Clear msg->flags in previously sent messages, so that
+		 * they're ready for xpc_allocate_msg().
+		 */
+		xpc_clear_local_msgqueue_flags(ch);
+
+		(volatile s64) ch->w_remote_GP.get = ch->remote_GP.get;
+
+		dev_dbg(xpc_chan, "w_remote_GP.get changed to %ld, partid=%d, "
+			"channel=%d\n", ch->w_remote_GP.get, ch->partid,
+			ch->number);
+
+		/*
+		 * If anyone was waiting for message queue entries to become
+		 * available, wake them up.
+		 */
+		if (atomic_read(&ch->n_on_msg_allocate_wq) > 0) {
+			wake_up(&ch->msg_allocate_wq);
+		}
+	}
+
+
+	/*
+	 * Now check for newly sent messages by the other side. (The remote
+	 * PUT value will have changed since we last looked at it.)
+	 */
+
+	if (ch->w_remote_GP.put != ch->remote_GP.put) {
+		/*
+		 * Clear msg->flags in previously received messages, so that
+		 * they're ready for xpc_get_deliverable_msg().
+		 */
+		xpc_clear_remote_msgqueue_flags(ch);
+
+		(volatile s64) ch->w_remote_GP.put = ch->remote_GP.put;
+
+		dev_dbg(xpc_chan, "w_remote_GP.put changed to %ld, partid=%d, "
+			"channel=%d\n", ch->w_remote_GP.put, ch->partid,
+			ch->number);
+
+		nmsgs_sent = ch->w_remote_GP.put - ch->w_local_GP.get;
+		if (nmsgs_sent > 0) {
+			dev_dbg(xpc_chan, "msgs waiting to be copied and "
+				"delivered=%d, partid=%d, channel=%d\n",
+				nmsgs_sent, ch->partid, ch->number);
+
+			if (ch->flags & XPC_C_CONNECTCALLOUT) {
+				xpc_activate_kthreads(ch, nmsgs_sent);
+			}
+		}
+	}
+
+	xpc_msgqueue_deref(ch);
+}
+
+
+void
+xpc_process_channel_activity(struct xpc_partition *part)
+{
+	unsigned long irq_flags;
+	u64 IPI_amo, IPI_flags;
+	struct xpc_channel *ch;
+	int ch_number;
+
+
+	IPI_amo = xpc_get_IPI_flags(part);
+
+	/*
+	 * Initiate channel connections for registered channels.
+	 *
+	 * For each connected channel that has pending messages activate idle
+	 * kthreads and/or create new kthreads as needed.
+	 */
+
+	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
+		ch = &part->channels[ch_number];
+
+
+		/*
+		 * Process any open or close related IPI flags, and then deal
+		 * with connecting or disconnecting the channel as required.
+		 */
+
+		IPI_flags = XPC_GET_IPI_FLAGS(IPI_amo, ch_number);
+
+		if (XPC_ANY_OPENCLOSE_IPI_FLAGS_SET(IPI_flags)) {
+			xpc_process_openclose_IPI(part, ch_number, IPI_flags);
+		}
+
+
+		if (ch->flags & XPC_C_DISCONNECTING) {
+			spin_lock_irqsave(&ch->lock, irq_flags);
+			xpc_process_disconnect(ch, &irq_flags);
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+			continue;
+		}
+
+		if (part->act_state == XPC_P_DEACTIVATING) {
+			continue;
+		}
+
+		if (!(ch->flags & XPC_C_CONNECTED)) {
+			if (!(ch->flags & XPC_C_OPENREQUEST)) {
+				DBUG_ON(ch->flags & XPC_C_SETUP);
+				(void) xpc_connect_channel(ch);
+			} else {
+				spin_lock_irqsave(&ch->lock, irq_flags);
+				xpc_process_connect(ch, &irq_flags);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+			}
+			continue;
+		}
+
+
+		/*
+		 * Process any message related IPI flags, this may involve the
+		 * activation of kthreads to deliver any pending messages sent
+		 * from the other partition.
+		 */
+
+		if (XPC_ANY_MSG_IPI_FLAGS_SET(IPI_flags)) {
+			xpc_process_msg_IPI(part, ch_number);
+		}
+	}
+}
+
+
+/*
+ * XPC's heartbeat code calls this function to inform XPC that a partition has
+ * gone down.  XPC responds by tearing down the XPartition Communication
+ * infrastructure used for the just downed partition.
+ *
+ * XPC's heartbeat code will never call this function and xpc_partition_up()
+ * at the same time. Nor will it ever make multiple calls to either function
+ * at the same time.
+ */
+void
+xpc_partition_down(struct xpc_partition *part, enum xpc_retval reason)
+{
+	unsigned long irq_flags;
+	int ch_number;
+	struct xpc_channel *ch;
+
+
+	dev_dbg(xpc_chan, "deactivating partition %d, reason=%d\n",
+		XPC_PARTID(part), reason);
+
+	if (!xpc_part_ref(part)) {
+		/* infrastructure for this partition isn't currently set up */
+		return;
+	}
+
+
+	/* disconnect all channels associated with the downed partition */
+
+	for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
+		ch = &part->channels[ch_number];
+
+
+		xpc_msgqueue_ref(ch);
+		spin_lock_irqsave(&ch->lock, irq_flags);
+
+		XPC_DISCONNECT_CHANNEL(ch, reason, &irq_flags);
+
+		spin_unlock_irqrestore(&ch->lock, irq_flags);
+		xpc_msgqueue_deref(ch);
+	}
+
+	xpc_wakeup_channel_mgr(part);
+
+	xpc_part_deref(part);
+}
+
+
+/*
+ * Teardown the infrastructure necessary to support XPartition Communication
+ * between the specified remote partition and the local one.
+ */
+void
+xpc_teardown_infrastructure(struct xpc_partition *part)
+{
+	partid_t partid = XPC_PARTID(part);
+
+
+	/*
+	 * We start off by making this partition inaccessible to local
+	 * processes by marking it as no longer setup. Then we make it
+	 * inaccessible to remote processes by clearing the XPC per partition
+	 * specific variable's magic # (which indicates that these variables
+	 * are no longer valid) and by ignoring all XPC notify IPIs sent to
+	 * this partition.
+	 */
+
+	DBUG_ON(atomic_read(&part->nchannels_active) != 0);
+	DBUG_ON(part->setup_state != XPC_P_SETUP);
+	part->setup_state = XPC_P_WTEARDOWN;
+
+	xpc_vars_part[partid].magic = 0;
+
+
+	free_irq(SGI_XPC_NOTIFY, (void *) (u64) partid);
+
+
+	/*
+	 * Before proceding with the teardown we have to wait until all
+	 * existing references cease.
+	 */
+	wait_event(part->teardown_wq, (atomic_read(&part->references) == 0));
+
+
+	/* now we can begin tearing down the infrastructure */
+
+	part->setup_state = XPC_P_TORNDOWN;
+
+	/* in case we've still got outstanding timers registered... */
+	del_timer_sync(&part->dropped_IPI_timer);
+
+	kfree(part->remote_openclose_args_base);
+	part->remote_openclose_args = NULL;
+	kfree(part->local_openclose_args_base);
+	part->local_openclose_args = NULL;
+	kfree(part->remote_GPs_base);
+	part->remote_GPs = NULL;
+	kfree(part->local_GPs_base);
+	part->local_GPs = NULL;
+	kfree(part->channels);
+	part->channels = NULL;
+	part->local_IPI_amo_va = NULL;
+}
+
+
+/*
+ * Called by XP at the time of channel connection registration to cause
+ * XPC to establish connections to all currently active partitions.
+ */
+void
+xpc_initiate_connect(int ch_number)
+{
+	partid_t partid;
+	struct xpc_partition *part;
+	struct xpc_channel *ch;
+
+
+	DBUG_ON(ch_number < 0 || ch_number >= XPC_NCHANNELS);
+
+	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+		part = &xpc_partitions[partid];
+
+		if (xpc_part_ref(part)) {
+			ch = &part->channels[ch_number];
+
+			if (!(ch->flags & XPC_C_DISCONNECTING)) {
+				DBUG_ON(ch->flags & XPC_C_OPENREQUEST);
+				DBUG_ON(ch->flags & XPC_C_CONNECTED);
+				DBUG_ON(ch->flags & XPC_C_SETUP);
+
+				/*
+				 * Initiate the establishment of a connection
+				 * on the newly registered channel to the
+				 * remote partition.
+				 */
+				xpc_wakeup_channel_mgr(part);
+			}
+
+			xpc_part_deref(part);
+		}
+	}
+}
+
+
+void
+xpc_connected_callout(struct xpc_channel *ch)
+{
+	unsigned long irq_flags;
+
+
+	/* let the registerer know that a connection has been established */
+
+	if (ch->func != NULL) {
+		dev_dbg(xpc_chan, "ch->func() called, reason=xpcConnected, "
+			"partid=%d, channel=%d\n", ch->partid, ch->number);
+
+		ch->func(xpcConnected, ch->partid, ch->number,
+				(void *) (u64) ch->local_nentries, ch->key);
+
+		dev_dbg(xpc_chan, "ch->func() returned, reason=xpcConnected, "
+			"partid=%d, channel=%d\n", ch->partid, ch->number);
+	}
+
+	spin_lock_irqsave(&ch->lock, irq_flags);
+	ch->flags |= XPC_C_CONNECTCALLOUT;
+	spin_unlock_irqrestore(&ch->lock, irq_flags);
+}
+
+
+/*
+ * Called by XP at the time of channel connection unregistration to cause
+ * XPC to teardown all current connections for the specified channel.
+ *
+ * Before returning xpc_initiate_disconnect() will wait until all connections
+ * on the specified channel have been closed/torndown. So the caller can be
+ * assured that they will not be receiving any more callouts from XPC to the
+ * function they registered via xpc_connect().
+ *
+ * Arguments:
+ *
+ *	ch_number - channel # to unregister.
+ */
+void
+xpc_initiate_disconnect(int ch_number)
+{
+	unsigned long irq_flags;
+	partid_t partid;
+	struct xpc_partition *part;
+	struct xpc_channel *ch;
+
+
+	DBUG_ON(ch_number < 0 || ch_number >= XPC_NCHANNELS);
+
+	/* initiate the channel disconnect for every active partition */
+	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+		part = &xpc_partitions[partid];
+
+		if (xpc_part_ref(part)) {
+			ch = &part->channels[ch_number];
+			xpc_msgqueue_ref(ch);
+
+			spin_lock_irqsave(&ch->lock, irq_flags);
+
+			XPC_DISCONNECT_CHANNEL(ch, xpcUnregistering,
+								&irq_flags);
+
+			spin_unlock_irqrestore(&ch->lock, irq_flags);
+
+			xpc_msgqueue_deref(ch);
+			xpc_part_deref(part);
+		}
+	}
+
+	xpc_disconnect_wait(ch_number);
+}
+
+
+/*
+ * To disconnect a channel, and reflect it back to all who may be waiting.
+ *
+ * >>> An OPEN is not allowed until XPC_C_DISCONNECTING is cleared by
+ * >>> xpc_free_msgqueues().
+ *
+ * THE CHANNEL IS TO BE LOCKED BY THE CALLER AND WILL REMAIN LOCKED UPON RETURN.
+ */
+void
+xpc_disconnect_channel(const int line, struct xpc_channel *ch,
+			enum xpc_retval reason, unsigned long *irq_flags)
+{
+	u32 flags;
+
+
+	DBUG_ON(!spin_is_locked(&ch->lock));
+
+	if (ch->flags & (XPC_C_DISCONNECTING | XPC_C_DISCONNECTED)) {
+		return;
+	}
+	DBUG_ON(!(ch->flags & (XPC_C_CONNECTING | XPC_C_CONNECTED)));
+
+	dev_dbg(xpc_chan, "reason=%d, line=%d, partid=%d, channel=%d\n",
+		reason, line, ch->partid, ch->number);
+
+	XPC_SET_REASON(ch, reason, line);
+
+	flags = ch->flags;
+	/* some of these may not have been set */
+	ch->flags &= ~(XPC_C_OPENREQUEST | XPC_C_OPENREPLY |
+			XPC_C_ROPENREQUEST | XPC_C_ROPENREPLY |
+			XPC_C_CONNECTING | XPC_C_CONNECTED);
+
+	ch->flags |= (XPC_C_CLOSEREQUEST | XPC_C_DISCONNECTING);
+	xpc_IPI_send_closerequest(ch, irq_flags);
+
+	if (flags & XPC_C_CONNECTED) {
+		ch->flags |= XPC_C_WASCONNECTED;
+	}
+
+	if (atomic_read(&ch->kthreads_idle) > 0) {
+		/* wake all idle kthreads so they can exit */
+		wake_up_all(&ch->idle_wq);
+	}
+
+	spin_unlock_irqrestore(&ch->lock, *irq_flags);
+
+
+	/* wake those waiting to allocate an entry from the local msg queue */
+
+	if (atomic_read(&ch->n_on_msg_allocate_wq) > 0) {
+		wake_up(&ch->msg_allocate_wq);
+	}
+
+	/* wake those waiting for notify completion */
+
+	if (atomic_read(&ch->n_to_notify) > 0) {
+		xpc_notify_senders(ch, reason, ch->w_local_GP.put);
+	}
+
+	spin_lock_irqsave(&ch->lock, *irq_flags);
+}
+
+
+void
+xpc_disconnected_callout(struct xpc_channel *ch)
+{
+	/*
+	 * Let the channel's registerer know that the channel is now
+	 * disconnected. We don't want to do this if the registerer was never
+	 * informed of a connection being made, unless the disconnect was for
+	 * abnormal reasons.
+	 */
+
+	if (ch->func != NULL) {
+		dev_dbg(xpc_chan, "ch->func() called, reason=%d, partid=%d, "
+			"channel=%d\n", ch->reason, ch->partid, ch->number);
+
+		ch->func(ch->reason, ch->partid, ch->number, NULL, ch->key);
+
+		dev_dbg(xpc_chan, "ch->func() returned, reason=%d, partid=%d, "
+			"channel=%d\n", ch->reason, ch->partid, ch->number);
+	}
+}
+
+
+/*
+ * Wait for a message entry to become available for the specified channel,
+ * but don't wait any longer than 1 jiffy.
+ */
+static enum xpc_retval
+xpc_allocate_msg_wait(struct xpc_channel *ch)
+{
+	enum xpc_retval ret;
+
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		DBUG_ON(ch->reason == xpcInterrupted);  // >>> Is this true?
+		return ch->reason;
+	}
+
+	atomic_inc(&ch->n_on_msg_allocate_wq);
+	ret = interruptible_sleep_on_timeout(&ch->msg_allocate_wq, 1);
+	atomic_dec(&ch->n_on_msg_allocate_wq);
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		ret = ch->reason;
+		DBUG_ON(ch->reason == xpcInterrupted);  // >>> Is this true?
+	} else if (ret == 0) {
+		ret = xpcTimeout;
+	} else {
+		ret = xpcInterrupted;
+	}
+
+	return ret;
+}
+
+
+/*
+ * Allocate an entry for a message from the message queue associated with the
+ * specified channel.
+ */
+static enum xpc_retval
+xpc_allocate_msg(struct xpc_channel *ch, u32 flags,
+			struct xpc_msg **address_of_msg)
+{
+	struct xpc_msg *msg;
+	enum xpc_retval ret;
+	s64 put;
+
+
+	/* this reference will be dropped in xpc_send_msg() */
+	xpc_msgqueue_ref(ch);
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		xpc_msgqueue_deref(ch);
+		return ch->reason;
+	}
+	if (!(ch->flags & XPC_C_CONNECTED)) {
+		xpc_msgqueue_deref(ch);
+		return xpcNotConnected;
+	}
+
+
+	/*
+	 * Get the next available message entry from the local message queue.
+	 * If none are available, we'll make sure that we grab the latest
+	 * GP values.
+	 */
+	ret = xpcTimeout;
+
+	while (1) {
+
+		put = (volatile s64) ch->w_local_GP.put;
+		if (put - (volatile s64) ch->w_remote_GP.get <
+							ch->local_nentries) {
+
+			/* There are available message entries. We need to try
+			 * to secure one for ourselves. We'll do this by trying
+			 * to increment w_local_GP.put as long as someone else
+			 * doesn't beat us to it. If they do, we'll have to
+			 * try again.
+		 	 */
+			if (cmpxchg(&ch->w_local_GP.put, put, put + 1) ==
+									put) {
+				/* we got the entry referenced by put */
+				break;
+			}
+			continue;	/* try again */
+		}
+
+
+		/*
+		 * There aren't any available msg entries at this time.
+		 *
+		 * In waiting for a message entry to become available,
+		 * we set a timeout in case the other side is not
+		 * sending completion IPIs. This lets us fake an IPI
+		 * that will cause the IPI handler to fetch the latest
+		 * GP values as if an IPI was sent by the other side.
+		 */
+		if (ret == xpcTimeout) {
+			xpc_IPI_send_local_msgrequest(ch);
+		}
+
+		if (flags & XPC_NOWAIT) {
+			xpc_msgqueue_deref(ch);
+			return xpcNoWait;
+		}
+
+		ret = xpc_allocate_msg_wait(ch);
+		if (ret != xpcInterrupted && ret != xpcTimeout) {
+			xpc_msgqueue_deref(ch);
+			return ret;
+		}
+	}
+
+
+	/* get the message's address and initialize it */
+	msg = (struct xpc_msg *) ((u64) ch->local_msgqueue +
+				(put % ch->local_nentries) * ch->msg_size);
+
+
+	DBUG_ON(msg->flags != 0);
+	msg->number = put;
+
+	dev_dbg(xpc_chan, "w_local_GP.put changed to %ld; msg=0x%p, "
+		"msg_number=%ld, partid=%d, channel=%d\n", put + 1,
+		(void *) msg, msg->number, ch->partid, ch->number);
+
+	*address_of_msg = msg;
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Allocate an entry for a message from the message queue associated with the
+ * specified channel. NOTE that this routine can sleep waiting for a message
+ * entry to become available. To not sleep, pass in the XPC_NOWAIT flag.
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel #.
+ *	flags - see xpc.h for valid flags.
+ *	payload - address of the allocated payload area pointer (filled in on
+ * 	          return) in which the user-defined message is constructed.
+ */
+enum xpc_retval
+xpc_initiate_allocate(partid_t partid, int ch_number, u32 flags, void **payload)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	enum xpc_retval ret = xpcUnknownReason;
+	struct xpc_msg *msg;
+
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+
+	*payload = NULL;
+
+	if (xpc_part_ref(part)) {
+		ret = xpc_allocate_msg(&part->channels[ch_number], flags, &msg);
+		xpc_part_deref(part);
+
+		if (msg != NULL) {
+			*payload = &msg->payload;
+		}
+	}
+
+	return ret;
+}
+
+
+/*
+ * Now we actually send the messages that are ready to be sent by advancing
+ * the local message queue's Put value and then send an IPI to the recipient
+ * partition.
+ */
+static void
+xpc_send_msgs(struct xpc_channel *ch, s64 initial_put)
+{
+	struct xpc_msg *msg;
+	s64 put = initial_put + 1;
+	int send_IPI = 0;
+
+
+	while (1) {
+
+		while (1) {
+			if (put == (volatile s64) ch->w_local_GP.put) {
+				break;
+			}
+
+			msg = (struct xpc_msg *) ((u64) ch->local_msgqueue +
+			       (put % ch->local_nentries) * ch->msg_size);
+
+			if (!(msg->flags & XPC_M_READY)) {
+				break;
+			}
+
+			put++;
+		}
+
+		if (put == initial_put) {
+			/* nothing's changed */
+			break;
+		}
+
+		if (cmpxchg_rel(&ch->local_GP->put, initial_put, put) !=
+								initial_put) {
+			/* someone else beat us to it */
+			DBUG_ON((volatile s64) ch->local_GP->put < initial_put);
+			break;
+		}
+
+		/* we just set the new value of local_GP->put */
+
+		dev_dbg(xpc_chan, "local_GP->put changed to %ld, partid=%d, "
+			"channel=%d\n", put, ch->partid, ch->number);
+
+		send_IPI = 1;
+
+		/*
+		 * We need to ensure that the message referenced by
+		 * local_GP->put is not XPC_M_READY or that local_GP->put
+		 * equals w_local_GP.put, so we'll go have a look.
+		 */
+		initial_put = put;
+	}
+
+	if (send_IPI) {
+		xpc_IPI_send_msgrequest(ch);
+	}
+}
+
+
+/*
+ * Common code that does the actual sending of the message by advancing the
+ * local message queue's Put value and sends an IPI to the partition the
+ * message is being sent to.
+ */
+static enum xpc_retval
+xpc_send_msg(struct xpc_channel *ch, struct xpc_msg *msg, u8 notify_type,
+			xpc_notify_func func, void *key)
+{
+	enum xpc_retval ret = xpcSuccess;
+	struct xpc_notify *notify = NULL;   // >>> to keep the compiler happy!!
+	s64 put, msg_number = msg->number;
+
+
+	DBUG_ON(notify_type == XPC_N_CALL && func == NULL);
+	DBUG_ON((((u64) msg - (u64) ch->local_msgqueue) / ch->msg_size) !=
+					msg_number % ch->local_nentries);
+	DBUG_ON(msg->flags & XPC_M_READY);
+
+	if (ch->flags & XPC_C_DISCONNECTING) {
+		/* drop the reference grabbed in xpc_allocate_msg() */
+		xpc_msgqueue_deref(ch);
+		return ch->reason;
+	}
+
+	if (notify_type != 0) {
+		/*
+		 * Tell the remote side to send an ACK interrupt when the
+		 * message has been delivered.
+		 */
+		msg->flags |= XPC_M_INTERRUPT;
+
+		atomic_inc(&ch->n_to_notify);
+
+		notify = &ch->notify_queue[msg_number % ch->local_nentries];
+		notify->func = func;
+		notify->key = key;
+		(volatile u8) notify->type = notify_type;
+
+		// >>> is a mb() needed here?
+
+		if (ch->flags & XPC_C_DISCONNECTING) {
+			/*
+			 * An error occurred between our last error check and
+			 * this one. We will try to clear the type field from
+			 * the notify entry. If we succeed then
+			 * xpc_disconnect_channel() didn't already process
+			 * the notify entry.
+			 */
+			if (cmpxchg(&notify->type, notify_type, 0) ==
+								notify_type) {
+				atomic_dec(&ch->n_to_notify);
+				ret = ch->reason;
+			}
+
+			/* drop the reference grabbed in xpc_allocate_msg() */
+			xpc_msgqueue_deref(ch);
+			return ret;
+		}
+	}
+
+	msg->flags |= XPC_M_READY;
+
+	/*
+	 * The preceding store of msg->flags must occur before the following
+	 * load of ch->local_GP->put.
+	 */
+	mb();
+
+	/* see if the message is next in line to be sent, if so send it */
+
+	put = ch->local_GP->put;
+	if (put == msg_number) {
+		xpc_send_msgs(ch, put);
+	}
+
+	/* drop the reference grabbed in xpc_allocate_msg() */
+	xpc_msgqueue_deref(ch);
+	return ret;
+}
+
+
+/*
+ * Send a message previously allocated using xpc_initiate_allocate() on the
+ * specified channel connected to the specified partition.
+ *
+ * This routine will not wait for the message to be received, nor will
+ * notification be given when it does happen. Once this routine has returned
+ * the message entry allocated via xpc_initiate_allocate() is no longer
+ * accessable to the caller.
+ *
+ * This routine, although called by users, does not call xpc_part_ref() to
+ * ensure that the partition infrastructure is in place. It relies on the
+ * fact that we called xpc_msgqueue_ref() in xpc_allocate_msg().
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel # to send message on.
+ *	payload - pointer to the payload area allocated via
+ *			xpc_initiate_allocate().
+ */
+enum xpc_retval
+xpc_initiate_send(partid_t partid, int ch_number, void *payload)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);
+	enum xpc_retval ret;
+
+
+	dev_dbg(xpc_chan, "msg=0x%p, partid=%d, channel=%d\n", (void *) msg,
+		partid, ch_number);
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+	DBUG_ON(msg == NULL);
+
+	ret = xpc_send_msg(&part->channels[ch_number], msg, 0, NULL, NULL);
+
+	return ret;
+}
+
+
+/*
+ * Send a message previously allocated using xpc_initiate_allocate on the
+ * specified channel connected to the specified partition.
+ *
+ * This routine will not wait for the message to be sent. Once this routine
+ * has returned the message entry allocated via xpc_initiate_allocate() is no
+ * longer accessable to the caller.
+ *
+ * Once the remote end of the channel has received the message, the function
+ * passed as an argument to xpc_initiate_send_notify() will be called. This
+ * allows the sender to free up or re-use any buffers referenced by the
+ * message, but does NOT mean the message has been processed at the remote
+ * end by a receiver.
+ *
+ * If this routine returns an error, the caller's function will NOT be called.
+ *
+ * This routine, although called by users, does not call xpc_part_ref() to
+ * ensure that the partition infrastructure is in place. It relies on the
+ * fact that we called xpc_msgqueue_ref() in xpc_allocate_msg().
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel # to send message on.
+ *	payload - pointer to the payload area allocated via
+ *			xpc_initiate_allocate().
+ *	func - function to call with asynchronous notification of message
+ *		  receipt. THIS FUNCTION MUST BE NON-BLOCKING.
+ *	key - user-defined key to be passed to the function when it's called.
+ */
+enum xpc_retval
+xpc_initiate_send_notify(partid_t partid, int ch_number, void *payload,
+				xpc_notify_func func, void *key)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);
+	enum xpc_retval ret;
+
+
+	dev_dbg(xpc_chan, "msg=0x%p, partid=%d, channel=%d\n", (void *) msg,
+		partid, ch_number);
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+	DBUG_ON(msg == NULL);
+	DBUG_ON(func == NULL);
+
+	ret = xpc_send_msg(&part->channels[ch_number], msg, XPC_N_CALL,
+								func, key);
+	return ret;
+}
+
+
+static struct xpc_msg *
+xpc_pull_remote_msg(struct xpc_channel *ch, s64 get)
+{
+	struct xpc_partition *part = &xpc_partitions[ch->partid];
+	struct xpc_msg *remote_msg, *msg;
+	u32 msg_index, nmsgs;
+	u64 msg_offset;
+	enum xpc_retval ret;
+
+
+	if (down_interruptible(&ch->msg_to_pull_sema) != 0) {
+		/* we were interrupted by a signal */
+		return NULL;
+	}
+
+	while (get >= ch->next_msg_to_pull) {
+
+		/* pull as many messages as are ready and able to be pulled */
+
+		msg_index = ch->next_msg_to_pull % ch->remote_nentries;
+
+		DBUG_ON(ch->next_msg_to_pull >=
+					(volatile s64) ch->w_remote_GP.put);
+		nmsgs =  (volatile s64) ch->w_remote_GP.put -
+						ch->next_msg_to_pull;
+		if (msg_index + nmsgs > ch->remote_nentries) {
+			/* ignore the ones that wrap the msg queue for now */
+			nmsgs = ch->remote_nentries - msg_index;
+		}
+
+		msg_offset = msg_index * ch->msg_size;
+		msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue +
+								msg_offset);
+		remote_msg = (struct xpc_msg *) (ch->remote_msgqueue_pa +
+								msg_offset);
+
+		if ((ret = xpc_pull_remote_cachelines(part, msg, remote_msg,
+				nmsgs * ch->msg_size)) != xpcSuccess) {
+
+			dev_dbg(xpc_chan, "failed to pull %d msgs starting with"
+				" msg %ld from partition %d, channel=%d, "
+				"ret=%d\n", nmsgs, ch->next_msg_to_pull,
+				ch->partid, ch->number, ret);
+
+			XPC_DEACTIVATE_PARTITION(part, ret);
+
+			up(&ch->msg_to_pull_sema);
+			return NULL;
+		}
+
+		mb();	/* >>> this may not be needed, we're not sure */
+
+		ch->next_msg_to_pull += nmsgs;
+	}
+
+	up(&ch->msg_to_pull_sema);
+
+	/* return the message we were looking for */
+	msg_offset = (get % ch->remote_nentries) * ch->msg_size;
+	msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue + msg_offset);
+
+	return msg;
+}
+
+
+/*
+ * Get a message to be delivered.
+ */
+static struct xpc_msg *
+xpc_get_deliverable_msg(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg = NULL;
+	s64 get;
+
+
+	do {
+		if ((volatile u32) ch->flags & XPC_C_DISCONNECTING) {
+			break;
+		}
+
+		get = (volatile s64) ch->w_local_GP.get;
+		if (get == (volatile s64) ch->w_remote_GP.put) {
+			break;
+		}
+
+		/* There are messages waiting to be pulled and delivered.
+		 * We need to try to secure one for ourselves. We'll do this
+		 * by trying to increment w_local_GP.get and hope that no one
+		 * else beats us to it. If they do, we'll we'll simply have
+		 * to try again for the next one.
+	 	 */
+
+		if (cmpxchg(&ch->w_local_GP.get, get, get + 1) == get) {
+			/* we got the entry referenced by get */
+
+			dev_dbg(xpc_chan, "w_local_GP.get changed to %ld, "
+				"partid=%d, channel=%d\n", get + 1,
+				ch->partid, ch->number);
+
+			/* pull the message from the remote partition */
+
+			msg = xpc_pull_remote_msg(ch, get);
+
+			DBUG_ON(msg != NULL && msg->number != get);
+			DBUG_ON(msg != NULL && (msg->flags & XPC_M_DONE));
+			DBUG_ON(msg != NULL && !(msg->flags & XPC_M_READY));
+
+			break;
+		}
+
+	} while (1);
+
+	return msg;
+}
+
+
+/*
+ * Deliver a message to its intended recipient.
+ */
+void
+xpc_deliver_msg(struct xpc_channel *ch)
+{
+	struct xpc_msg *msg;
+
+
+	if ((msg = xpc_get_deliverable_msg(ch)) != NULL) {
+
+		/*
+		 * This ref is taken to protect the payload itself from being
+		 * freed before the user is finished with it, which the user
+		 * indicates by calling xpc_initiate_received().
+		 */
+		xpc_msgqueue_ref(ch);
+
+		atomic_inc(&ch->kthreads_active);
+
+		if (ch->func != NULL) {
+			dev_dbg(xpc_chan, "ch->func() called, msg=0x%p, "
+				"msg_number=%ld, partid=%d, channel=%d\n",
+				(void *) msg, msg->number, ch->partid,
+				ch->number);
+
+			/* deliver the message to its intended recipient */
+			ch->func(xpcMsgReceived, ch->partid, ch->number,
+					&msg->payload, ch->key);
+
+			dev_dbg(xpc_chan, "ch->func() returned, msg=0x%p, "
+				"msg_number=%ld, partid=%d, channel=%d\n",
+				(void *) msg, msg->number, ch->partid,
+				ch->number);
+		}
+
+		atomic_dec(&ch->kthreads_active);
+	}
+}
+
+
+/*
+ * Now we actually acknowledge the messages that have been delivered and ack'd
+ * by advancing the cached remote message queue's Get value and if requested
+ * send an IPI to the message sender's partition.
+ */
+static void
+xpc_acknowledge_msgs(struct xpc_channel *ch, s64 initial_get, u8 msg_flags)
+{
+	struct xpc_msg *msg;
+	s64 get = initial_get + 1;
+	int send_IPI = 0;
+
+
+	while (1) {
+
+		while (1) {
+			if (get == (volatile s64) ch->w_local_GP.get) {
+				break;
+			}
+
+			msg = (struct xpc_msg *) ((u64) ch->remote_msgqueue +
+			       (get % ch->remote_nentries) * ch->msg_size);
+
+			if (!(msg->flags & XPC_M_DONE)) {
+				break;
+			}
+
+			msg_flags |= msg->flags;
+			get++;
+		}
+
+		if (get == initial_get) {
+			/* nothing's changed */
+			break;
+		}
+
+		if (cmpxchg_rel(&ch->local_GP->get, initial_get, get) !=
+								initial_get) {
+			/* someone else beat us to it */
+			DBUG_ON((volatile s64) ch->local_GP->get <=
+								initial_get);
+			break;
+		}
+
+		/* we just set the new value of local_GP->get */
+
+		dev_dbg(xpc_chan, "local_GP->get changed to %ld, partid=%d, "
+			"channel=%d\n", get, ch->partid, ch->number);
+
+		send_IPI = (msg_flags & XPC_M_INTERRUPT);
+
+		/*
+		 * We need to ensure that the message referenced by
+		 * local_GP->get is not XPC_M_DONE or that local_GP->get
+		 * equals w_local_GP.get, so we'll go have a look.
+		 */
+		initial_get = get;
+	}
+
+	if (send_IPI) {
+		xpc_IPI_send_msgrequest(ch);
+	}
+}
+
+
+/*
+ * Acknowledge receipt of a delivered message.
+ *
+ * If a message has XPC_M_INTERRUPT set, send an interrupt to the partition
+ * that sent the message.
+ *
+ * This function, although called by users, does not call xpc_part_ref() to
+ * ensure that the partition infrastructure is in place. It relies on the
+ * fact that we called xpc_msgqueue_ref() in xpc_deliver_msg().
+ *
+ * Arguments:
+ *
+ *	partid - ID of partition to which the channel is connected.
+ *	ch_number - channel # message received on.
+ *	payload - pointer to the payload area allocated via
+ *			xpc_initiate_allocate().
+ */
+void
+xpc_initiate_received(partid_t partid, int ch_number, void *payload)
+{
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_channel *ch;
+	struct xpc_msg *msg = XPC_MSG_ADDRESS(payload);
+	s64 get, msg_number = msg->number;
+
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+	DBUG_ON(ch_number < 0 || ch_number >= part->nchannels);
+
+	ch = &part->channels[ch_number];
+
+	dev_dbg(xpc_chan, "msg=0x%p, msg_number=%ld, partid=%d, channel=%d\n",
+		(void *) msg, msg_number, ch->partid, ch->number);
+
+	DBUG_ON((((u64) msg - (u64) ch->remote_msgqueue) / ch->msg_size) !=
+					msg_number % ch->remote_nentries);
+	DBUG_ON(msg->flags & XPC_M_DONE);
+
+	msg->flags |= XPC_M_DONE;
+
+	/*
+	 * The preceding store of msg->flags must occur before the following
+	 * load of ch->local_GP->get.
+	 */
+	mb();
+
+	/*
+	 * See if this message is next in line to be acknowledged as having
+	 * been delivered.
+	 */
+	get = ch->local_GP->get;
+	if (get == msg_number) {
+		xpc_acknowledge_msgs(ch, get, msg->flags);
+	}
+
+	/* the call to xpc_msgqueue_ref() was done by xpc_deliver_msg()  */
+	xpc_msgqueue_deref(ch);
+}
+

arch/ia64/sn/kernel/xpc_main.c

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2004-2005 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+
+
+/*
+ * Cross Partition Communication (XPC) support - standard version.
+ *
+ *	XPC provides a message passing capability that crosses partition
+ *	boundaries. This module is made up of two parts:
+ *
+ *	    partition	This part detects the presence/absence of other
+ *			partitions. It provides a heartbeat and monitors
+ *			the heartbeats of other partitions.
+ *
+ *	    channel	This part manages the channels and sends/receives
+ *			messages across them to/from other partitions.
+ *
+ *	There are a couple of additional functions residing in XP, which
+ *	provide an interface to XPC for its users.
+ *
+ *
+ *	Caveats:
+ *
+ *	  . We currently have no way to determine which nasid an IPI came
+ *	    from. Thus, xpc_IPI_send() does a remote AMO write followed by
+ *	    an IPI. The AMO indicates where data is to be pulled from, so
+ *	    after the IPI arrives, the remote partition checks the AMO word.
+ *	    The IPI can actually arrive before the AMO however, so other code
+ *	    must periodically check for this case. Also, remote AMO operations
+ *	    do not reliably time out. Thus we do a remote PIO read solely to
+ *	    know whether the remote partition is down and whether we should
+ *	    stop sending IPIs to it. This remote PIO read operation is set up
+ *	    in a special nofault region so SAL knows to ignore (and cleanup)
+ *	    any errors due to the remote AMO write, PIO read, and/or PIO
+ *	    write operations.
+ *
+ *	    If/when new hardware solves this IPI problem, we should abandon
+ *	    the current approach.
+ *
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/syscalls.h>
+#include <linux/cache.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <asm/sn/intr.h>
+#include <asm/sn/sn_sal.h>
+#include <asm/uaccess.h>
+#include "xpc.h"
+
+
+/* define two XPC debug device structures to be used with dev_dbg() et al */
+
+struct device_driver xpc_dbg_name = {
+	.name = "xpc"
+};
+
+struct device xpc_part_dbg_subname = {
+	.bus_id = {0},		/* set to "part" at xpc_init() time */
+	.driver = &xpc_dbg_name
+};
+
+struct device xpc_chan_dbg_subname = {
+	.bus_id = {0},		/* set to "chan" at xpc_init() time */
+	.driver = &xpc_dbg_name
+};
+
+struct device *xpc_part = &xpc_part_dbg_subname;
+struct device *xpc_chan = &xpc_chan_dbg_subname;
+
+
+/* systune related variables for /proc/sys directories */
+
+static int xpc_hb_min = 1;
+static int xpc_hb_max = 10;
+
+static int xpc_hb_check_min = 10;
+static int xpc_hb_check_max = 120;
+
+static ctl_table xpc_sys_xpc_hb_dir[] = {
+	{
+		1,
+		"hb_interval",
+		&xpc_hb_interval,
+		sizeof(int),
+		0644,
+		NULL,
+		&proc_dointvec_minmax,
+		&sysctl_intvec,
+		NULL,
+		&xpc_hb_min, &xpc_hb_max
+	},
+	{
+		2,
+		"hb_check_interval",
+		&xpc_hb_check_interval,
+		sizeof(int),
+		0644,
+		NULL,
+		&proc_dointvec_minmax,
+		&sysctl_intvec,
+		NULL,
+		&xpc_hb_check_min, &xpc_hb_check_max
+	},
+	{0}
+};
+static ctl_table xpc_sys_xpc_dir[] = {
+	{
+		1,
+		"hb",
+		NULL,
+		0,
+		0555,
+		xpc_sys_xpc_hb_dir
+	},
+	{0}
+};
+static ctl_table xpc_sys_dir[] = {
+	{
+		1,
+		"xpc",
+		NULL,
+		0,
+		0555,
+		xpc_sys_xpc_dir
+	},
+	{0}
+};
+static struct ctl_table_header *xpc_sysctl;
+
+
+/* #of IRQs received */
+static atomic_t xpc_act_IRQ_rcvd;
+
+/* IRQ handler notifies this wait queue on receipt of an IRQ */
+static DECLARE_WAIT_QUEUE_HEAD(xpc_act_IRQ_wq);
+
+static unsigned long xpc_hb_check_timeout;
+
+/* xpc_hb_checker thread exited notification */
+static DECLARE_MUTEX_LOCKED(xpc_hb_checker_exited);
+
+/* xpc_discovery thread exited notification */
+static DECLARE_MUTEX_LOCKED(xpc_discovery_exited);
+
+
+static struct timer_list xpc_hb_timer;
+
+
+static void xpc_kthread_waitmsgs(struct xpc_partition *, struct xpc_channel *);
+
+
+/*
+ * Notify the heartbeat check thread that an IRQ has been received.
+ */
+static irqreturn_t
+xpc_act_IRQ_handler(int irq, void *dev_id, struct pt_regs *regs)
+{
+	atomic_inc(&xpc_act_IRQ_rcvd);
+	wake_up_interruptible(&xpc_act_IRQ_wq);
+	return IRQ_HANDLED;
+}
+
+
+/*
+ * Timer to produce the heartbeat.  The timer structures function is
+ * already set when this is initially called.  A tunable is used to
+ * specify when the next timeout should occur.
+ */
+static void
+xpc_hb_beater(unsigned long dummy)
+{
+	xpc_vars->heartbeat++;
+
+	if (jiffies >= xpc_hb_check_timeout) {
+		wake_up_interruptible(&xpc_act_IRQ_wq);
+	}
+
+	xpc_hb_timer.expires = jiffies + (xpc_hb_interval * HZ);
+	add_timer(&xpc_hb_timer);
+}
+
+
+/*
+ * This thread is responsible for nearly all of the partition
+ * activation/deactivation.
+ */
+static int
+xpc_hb_checker(void *ignore)
+{
+	int last_IRQ_count = 0;
+	int new_IRQ_count;
+	int force_IRQ=0;
+
+
+	/* this thread was marked active by xpc_hb_init() */
+
+	daemonize(XPC_HB_CHECK_THREAD_NAME);
+
+	set_cpus_allowed(current, cpumask_of_cpu(XPC_HB_CHECK_CPU));
+
+	xpc_hb_check_timeout = jiffies + (xpc_hb_check_interval * HZ);
+
+	while (!(volatile int) xpc_exiting) {
+
+		/* wait for IRQ or timeout */
+		(void) wait_event_interruptible(xpc_act_IRQ_wq,
+			    (last_IRQ_count < atomic_read(&xpc_act_IRQ_rcvd) ||
+					jiffies >= xpc_hb_check_timeout ||
+						(volatile int) xpc_exiting));
+
+		dev_dbg(xpc_part, "woke up with %d ticks rem; %d IRQs have "
+			"been received\n",
+			(int) (xpc_hb_check_timeout - jiffies),
+			atomic_read(&xpc_act_IRQ_rcvd) - last_IRQ_count);
+
+
+		/* checking of remote heartbeats is skewed by IRQ handling */
+		if (jiffies >= xpc_hb_check_timeout) {
+			dev_dbg(xpc_part, "checking remote heartbeats\n");
+			xpc_check_remote_hb();
+
+			/*
+			 * We need to periodically recheck to ensure no
+			 * IPI/AMO pairs have been missed.  That check
+			 * must always reset xpc_hb_check_timeout.
+			 */
+			force_IRQ = 1;
+		}
+
+
+		new_IRQ_count = atomic_read(&xpc_act_IRQ_rcvd);
+		if (last_IRQ_count < new_IRQ_count || force_IRQ != 0) {
+			force_IRQ = 0;
+
+			dev_dbg(xpc_part, "found an IRQ to process; will be "
+				"resetting xpc_hb_check_timeout\n");
+
+			last_IRQ_count += xpc_identify_act_IRQ_sender();
+			if (last_IRQ_count < new_IRQ_count) {
+				/* retry once to help avoid missing AMO */
+				(void) xpc_identify_act_IRQ_sender();
+			}
+			last_IRQ_count = new_IRQ_count;
+
+			xpc_hb_check_timeout = jiffies +
+					   (xpc_hb_check_interval * HZ);
+		}
+	}
+
+	dev_dbg(xpc_part, "heartbeat checker is exiting\n");
+
+
+	/* mark this thread as inactive */
+	up(&xpc_hb_checker_exited);
+	return 0;
+}
+
+
+/*
+ * This thread will attempt to discover other partitions to activate
+ * based on info provided by SAL. This new thread is short lived and
+ * will exit once discovery is complete.
+ */
+static int
+xpc_initiate_discovery(void *ignore)
+{
+	daemonize(XPC_DISCOVERY_THREAD_NAME);
+
+	xpc_discovery();
+
+	dev_dbg(xpc_part, "discovery thread is exiting\n");
+
+	/* mark this thread as inactive */
+	up(&xpc_discovery_exited);
+	return 0;
+}
+
+
+/*
+ * Establish first contact with the remote partititon. This involves pulling
+ * the XPC per partition variables from the remote partition and waiting for
+ * the remote partition to pull ours.
+ */
+static enum xpc_retval
+xpc_make_first_contact(struct xpc_partition *part)
+{
+	enum xpc_retval ret;
+
+
+	while ((ret = xpc_pull_remote_vars_part(part)) != xpcSuccess) {
+		if (ret != xpcRetry) {
+			XPC_DEACTIVATE_PARTITION(part, ret);
+			return ret;
+		}
+
+		dev_dbg(xpc_chan, "waiting to make first contact with "
+			"partition %d\n", XPC_PARTID(part));
+
+		/* wait a 1/4 of a second or so */
+		set_current_state(TASK_INTERRUPTIBLE);
+		(void) schedule_timeout(0.25 * HZ);
+
+		if (part->act_state == XPC_P_DEACTIVATING) {
+			return part->reason;
+		}
+	}
+
+	return xpc_mark_partition_active(part);
+}
+
+
+/*
+ * The first kthread assigned to a newly activated partition is the one
+ * created by XPC HB with which it calls xpc_partition_up(). XPC hangs on to
+ * that kthread until the partition is brought down, at which time that kthread
+ * returns back to XPC HB. (The return of that kthread will signify to XPC HB
+ * that XPC has dismantled all communication infrastructure for the associated
+ * partition.) This kthread becomes the channel manager for that partition.
+ *
+ * Each active partition has a channel manager, who, besides connecting and
+ * disconnecting channels, will ensure that each of the partition's connected
+ * channels has the required number of assigned kthreads to get the work done.
+ */
+static void
+xpc_channel_mgr(struct xpc_partition *part)
+{
+	while (part->act_state != XPC_P_DEACTIVATING ||
+				atomic_read(&part->nchannels_active) > 0) {
+
+		xpc_process_channel_activity(part);
+
+
+		/*
+		 * Wait until we've been requested to activate kthreads or
+		 * all of the channel's message queues have been torn down or
+		 * a signal is pending.
+		 *
+		 * The channel_mgr_requests is set to 1 after being awakened,
+		 * This is done to prevent the channel mgr from making one pass
+		 * through the loop for each request, since he will
+		 * be servicing all the requests in one pass. The reason it's
+		 * set to 1 instead of 0 is so that other kthreads will know
+		 * that the channel mgr is running and won't bother trying to
+		 * wake him up.
+		 */
+		atomic_dec(&part->channel_mgr_requests);
+		(void) wait_event_interruptible(part->channel_mgr_wq,
+				(atomic_read(&part->channel_mgr_requests) > 0 ||
+				(volatile u64) part->local_IPI_amo != 0 ||
+				((volatile u8) part->act_state ==
+							XPC_P_DEACTIVATING &&
+				atomic_read(&part->nchannels_active) == 0)));
+		atomic_set(&part->channel_mgr_requests, 1);
+
+		// >>> Does it need to wakeup periodically as well? In case we
+		// >>> miscalculated the #of kthreads to wakeup or create?
+	}
+}
+
+
+/*
+ * When XPC HB determines that a partition has come up, it will create a new
+ * kthread and that kthread will call this function to attempt to set up the
+ * basic infrastructure used for Cross Partition Communication with the newly
+ * upped partition.
+ *
+ * The kthread that was created by XPC HB and which setup the XPC
+ * infrastructure will remain assigned to the partition until the partition
+ * goes down. At which time the kthread will teardown the XPC infrastructure
+ * and then exit.
+ *
+ * XPC HB will put the remote partition's XPC per partition specific variables
+ * physical address into xpc_partitions[partid].remote_vars_part_pa prior to
+ * calling xpc_partition_up().
+ */
+static void
+xpc_partition_up(struct xpc_partition *part)
+{
+	DBUG_ON(part->channels != NULL);
+
+	dev_dbg(xpc_chan, "activating partition %d\n", XPC_PARTID(part));
+
+	if (xpc_setup_infrastructure(part) != xpcSuccess) {
+		return;
+	}
+
+	/*
+	 * The kthread that XPC HB called us with will become the
+	 * channel manager for this partition. It will not return
+	 * back to XPC HB until the partition's XPC infrastructure
+	 * has been dismantled.
+	 */
+
+	(void) xpc_part_ref(part);	/* this will always succeed */
+
+	if (xpc_make_first_contact(part) == xpcSuccess) {
+		xpc_channel_mgr(part);
+	}
+
+	xpc_part_deref(part);
+
+	xpc_teardown_infrastructure(part);
+}
+
+
+static int
+xpc_activating(void *__partid)
+{
+	partid_t partid = (u64) __partid;
+	struct xpc_partition *part = &xpc_partitions[partid];
+	unsigned long irq_flags;
+	struct sched_param param = { sched_priority: MAX_USER_RT_PRIO - 1 };
+	int ret;
+
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+
+	if (part->act_state == XPC_P_DEACTIVATING) {
+		part->act_state = XPC_P_INACTIVE;
+		spin_unlock_irqrestore(&part->act_lock, irq_flags);
+		part->remote_rp_pa = 0;
+		return 0;
+	}
+
+	/* indicate the thread is activating */
+	DBUG_ON(part->act_state != XPC_P_ACTIVATION_REQ);
+	part->act_state = XPC_P_ACTIVATING;
+
+	XPC_SET_REASON(part, 0, 0);
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+
+	dev_dbg(xpc_part, "bringing partition %d up\n", partid);
+
+	daemonize("xpc%02d", partid);
+
+	/*
+	 * This thread needs to run at a realtime priority to prevent a
+	 * significant performance degradation.
+	 */
+	ret = sched_setscheduler(current, SCHED_FIFO, &param);
+	if (ret != 0) {
+		dev_warn(xpc_part, "unable to set pid %d to a realtime "
+			"priority, ret=%d\n", current->pid, ret);
+	}
+
+	/* allow this thread and its children to run on any CPU */
+	set_cpus_allowed(current, CPU_MASK_ALL);
+
+	/*
+	 * Register the remote partition's AMOs with SAL so it can handle
+	 * and cleanup errors within that address range should the remote
+	 * partition go down. We don't unregister this range because it is
+	 * difficult to tell when outstanding writes to the remote partition
+	 * are finished and thus when it is safe to unregister. This should
+	 * not result in wasted space in the SAL xp_addr_region table because
+	 * we should get the same page for remote_amos_page_pa after module
+	 * reloads and system reboots.
+	 */
+	if (sn_register_xp_addr_region(part->remote_amos_page_pa,
+							PAGE_SIZE, 1) < 0) {
+		dev_warn(xpc_part, "xpc_partition_up(%d) failed to register "
+			"xp_addr region\n", partid);
+
+		spin_lock_irqsave(&part->act_lock, irq_flags);
+		part->act_state = XPC_P_INACTIVE;
+		XPC_SET_REASON(part, xpcPhysAddrRegFailed, __LINE__);
+		spin_unlock_irqrestore(&part->act_lock, irq_flags);
+		part->remote_rp_pa = 0;
+		return 0;
+	}
+
+	XPC_ALLOW_HB(partid, xpc_vars);
+	xpc_IPI_send_activated(part);
+
+
+	/*
+	 * xpc_partition_up() holds this thread and marks this partition as
+	 * XPC_P_ACTIVE by calling xpc_hb_mark_active().
+	 */
+	(void) xpc_partition_up(part);
+
+	xpc_mark_partition_inactive(part);
+
+	if (part->reason == xpcReactivating) {
+		/* interrupting ourselves results in activating partition */
+		xpc_IPI_send_reactivate(part);
+	}
+
+	return 0;
+}
+
+
+void
+xpc_activate_partition(struct xpc_partition *part)
+{
+	partid_t partid = XPC_PARTID(part);
+	unsigned long irq_flags;
+	pid_t pid;
+
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+
+	pid = kernel_thread(xpc_activating, (void *) ((u64) partid), 0);
+
+	DBUG_ON(part->act_state != XPC_P_INACTIVE);
+
+	if (pid > 0) {
+		part->act_state = XPC_P_ACTIVATION_REQ;
+		XPC_SET_REASON(part, xpcCloneKThread, __LINE__);
+	} else {
+		XPC_SET_REASON(part, xpcCloneKThreadFailed, __LINE__);
+	}
+
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+}
+
+
+/*
+ * Handle the receipt of a SGI_XPC_NOTIFY IRQ by seeing whether the specified
+ * partition actually sent it. Since SGI_XPC_NOTIFY IRQs may be shared by more
+ * than one partition, we use an AMO_t structure per partition to indicate
+ * whether a partition has sent an IPI or not.  >>> If it has, then wake up the
+ * associated kthread to handle it.
+ *
+ * All SGI_XPC_NOTIFY IRQs received by XPC are the result of IPIs sent by XPC
+ * running on other partitions.
+ *
+ * Noteworthy Arguments:
+ *
+ *	irq - Interrupt ReQuest number. NOT USED.
+ *
+ *	dev_id - partid of IPI's potential sender.
+ *
+ *	regs - processor's context before the processor entered
+ *	       interrupt code. NOT USED.
+ */
+irqreturn_t
+xpc_notify_IRQ_handler(int irq, void *dev_id, struct pt_regs *regs)
+{
+	partid_t partid = (partid_t) (u64) dev_id;
+	struct xpc_partition *part = &xpc_partitions[partid];
+
+
+	DBUG_ON(partid <= 0 || partid >= XP_MAX_PARTITIONS);
+
+	if (xpc_part_ref(part)) {
+		xpc_check_for_channel_activity(part);
+
+		xpc_part_deref(part);
+	}
+	return IRQ_HANDLED;
+}
+
+
+/*
+ * Check to see if xpc_notify_IRQ_handler() dropped any IPIs on the floor
+ * because the write to their associated IPI amo completed after the IRQ/IPI
+ * was received.
+ */
+void
+xpc_dropped_IPI_check(struct xpc_partition *part)
+{
+	if (xpc_part_ref(part)) {
+		xpc_check_for_channel_activity(part);
+
+		part->dropped_IPI_timer.expires = jiffies +
+							XPC_P_DROPPED_IPI_WAIT;
+		add_timer(&part->dropped_IPI_timer);
+		xpc_part_deref(part);
+	}
+}
+
+
+void
+xpc_activate_kthreads(struct xpc_channel *ch, int needed)
+{
+	int idle = atomic_read(&ch->kthreads_idle);
+	int assigned = atomic_read(&ch->kthreads_assigned);
+	int wakeup;
+
+
+	DBUG_ON(needed <= 0);
+
+	if (idle > 0) {
+		wakeup = (needed > idle) ? idle : needed;
+		needed -= wakeup;
+
+		dev_dbg(xpc_chan, "wakeup %d idle kthreads, partid=%d, "
+			"channel=%d\n", wakeup, ch->partid, ch->number);
+
+		/* only wakeup the requested number of kthreads */
+		wake_up_nr(&ch->idle_wq, wakeup);
+	}
+
+	if (needed <= 0) {
+		return;
+	}
+
+	if (needed + assigned > ch->kthreads_assigned_limit) {
+		needed = ch->kthreads_assigned_limit - assigned;
+		// >>>should never be less than 0
+		if (needed <= 0) {
+			return;
+		}
+	}
+
+	dev_dbg(xpc_chan, "create %d new kthreads, partid=%d, channel=%d\n",
+		needed, ch->partid, ch->number);
+
+	xpc_create_kthreads(ch, needed);
+}
+
+
+/*
+ * This function is where XPC's kthreads wait for messages to deliver.
+ */
+static void
+xpc_kthread_waitmsgs(struct xpc_partition *part, struct xpc_channel *ch)
+{
+	do {
+		/* deliver messages to their intended recipients */
+
+		while ((volatile s64) ch->w_local_GP.get <
+				(volatile s64) ch->w_remote_GP.put &&
+					!((volatile u32) ch->flags &
+						XPC_C_DISCONNECTING)) {
+			xpc_deliver_msg(ch);
+		}
+
+		if (atomic_inc_return(&ch->kthreads_idle) >
+						ch->kthreads_idle_limit) {
+			/* too many idle kthreads on this channel */
+			atomic_dec(&ch->kthreads_idle);
+			break;
+		}
+
+		dev_dbg(xpc_chan, "idle kthread calling "
+			"wait_event_interruptible_exclusive()\n");
+
+		(void) wait_event_interruptible_exclusive(ch->idle_wq,
+				((volatile s64) ch->w_local_GP.get <
+					(volatile s64) ch->w_remote_GP.put ||
+				((volatile u32) ch->flags &
+						XPC_C_DISCONNECTING)));
+
+		atomic_dec(&ch->kthreads_idle);
+
+	} while (!((volatile u32) ch->flags & XPC_C_DISCONNECTING));
+}
+
+
+static int
+xpc_daemonize_kthread(void *args)
+{
+	partid_t partid = XPC_UNPACK_ARG1(args);
+	u16 ch_number = XPC_UNPACK_ARG2(args);
+	struct xpc_partition *part = &xpc_partitions[partid];
+	struct xpc_channel *ch;
+	int n_needed;
+
+
+	daemonize("xpc%02dc%d", partid, ch_number);
+
+	dev_dbg(xpc_chan, "kthread starting, partid=%d, channel=%d\n",
+		partid, ch_number);
+
+	ch = &part->channels[ch_number];
+
+	if (!(ch->flags & XPC_C_DISCONNECTING)) {
+		DBUG_ON(!(ch->flags & XPC_C_CONNECTED));
+
+		/* let registerer know that connection has been established */
+
+		if (atomic_read(&ch->kthreads_assigned) == 1) {
+			xpc_connected_callout(ch);
+
+			/*
+			 * It is possible that while the callout was being
+			 * made that the remote partition sent some messages.
+			 * If that is the case, we may need to activate
+			 * additional kthreads to help deliver them. We only
+			 * need one less than total #of messages to deliver.
+			 */
+			n_needed = ch->w_remote_GP.put - ch->w_local_GP.get - 1;
+			if (n_needed > 0 &&
+					!(ch->flags & XPC_C_DISCONNECTING)) {
+				xpc_activate_kthreads(ch, n_needed);
+			}
+		}
+
+		xpc_kthread_waitmsgs(part, ch);
+	}
+
+	if (atomic_dec_return(&ch->kthreads_assigned) == 0 &&
+			((ch->flags & XPC_C_CONNECTCALLOUT) ||
+				(ch->reason != xpcUnregistering &&
+					ch->reason != xpcOtherUnregistering))) {
+		xpc_disconnected_callout(ch);
+	}
+
+
+	xpc_msgqueue_deref(ch);
+
+	dev_dbg(xpc_chan, "kthread exiting, partid=%d, channel=%d\n",
+		partid, ch_number);
+
+	xpc_part_deref(part);
+	return 0;
+}
+
+
+/*
+ * For each partition that XPC has established communications with, there is
+ * a minimum of one kernel thread assigned to perform any operation that
+ * may potentially sleep or block (basically the callouts to the asynchronous
+ * functions registered via xpc_connect()).
+ *
+ * Additional kthreads are created and destroyed by XPC as the workload
+ * demands.
+ *
+ * A kthread is assigned to one of the active channels that exists for a given
+ * partition.
+ */
+void
+xpc_create_kthreads(struct xpc_channel *ch, int needed)
+{
+	unsigned long irq_flags;
+	pid_t pid;
+	u64 args = XPC_PACK_ARGS(ch->partid, ch->number);
+
+
+	while (needed-- > 0) {
+		pid = kernel_thread(xpc_daemonize_kthread, (void *) args, 0);
+		if (pid < 0) {
+			/* the fork failed */
+
+			if (atomic_read(&ch->kthreads_assigned) <
+						ch->kthreads_idle_limit) {
+				/*
+				 * Flag this as an error only if we have an
+				 * insufficient #of kthreads for the channel
+				 * to function.
+				 *
+				 * No xpc_msgqueue_ref() is needed here since
+				 * the channel mgr is doing this.
+				 */
+				spin_lock_irqsave(&ch->lock, irq_flags);
+				XPC_DISCONNECT_CHANNEL(ch, xpcLackOfResources,
+								&irq_flags);
+				spin_unlock_irqrestore(&ch->lock, irq_flags);
+			}
+			break;
+		}
+
+		/*
+		 * The following is done on behalf of the newly created
+		 * kthread. That kthread is responsible for doing the
+		 * counterpart to the following before it exits.
+		 */
+		(void) xpc_part_ref(&xpc_partitions[ch->partid]);
+		xpc_msgqueue_ref(ch);
+		atomic_inc(&ch->kthreads_assigned);
+		ch->kthreads_created++;	// >>> temporary debug only!!!
+	}
+}
+
+
+void
+xpc_disconnect_wait(int ch_number)
+{
+	partid_t partid;
+	struct xpc_partition *part;
+	struct xpc_channel *ch;
+
+
+	/* now wait for all callouts to the caller's function to cease */
+	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+		part = &xpc_partitions[partid];
+
+		if (xpc_part_ref(part)) {
+			ch = &part->channels[ch_number];
+
+// >>> how do we keep from falling into the window between our check and going
+// >>> down and coming back up where sema is re-inited?
+			if (ch->flags & XPC_C_SETUP) {
+				(void) down(&ch->teardown_sema);
+			}
+
+			xpc_part_deref(part);
+		}
+	}
+}
+
+
+static void
+xpc_do_exit(void)
+{
+	partid_t partid;
+	int active_part_count;
+	struct xpc_partition *part;
+
+
+	/* now it's time to eliminate our heartbeat */
+	del_timer_sync(&xpc_hb_timer);
+	xpc_vars->heartbeating_to_mask = 0;
+
+	/* indicate to others that our reserved page is uninitialized */
+	xpc_rsvd_page->vars_pa = 0;
+
+	/*
+	 * Ignore all incoming interrupts. Without interupts the heartbeat
+	 * checker won't activate any new partitions that may come up.
+	 */
+	free_irq(SGI_XPC_ACTIVATE, NULL);
+
+	/*
+	 * Cause the heartbeat checker and the discovery threads to exit.
+	 * We don't want them attempting to activate new partitions as we
+	 * try to deactivate the existing ones.
+	 */
+	xpc_exiting = 1;
+	wake_up_interruptible(&xpc_act_IRQ_wq);
+
+	/* wait for the heartbeat checker thread to mark itself inactive */
+	down(&xpc_hb_checker_exited);
+
+	/* wait for the discovery thread to mark itself inactive */
+	down(&xpc_discovery_exited);
+
+
+	set_current_state(TASK_INTERRUPTIBLE);
+	schedule_timeout(0.3 * HZ);
+	set_current_state(TASK_RUNNING);
+
+
+	/* wait for all partitions to become inactive */
+
+	do {
+		active_part_count = 0;
+
+		for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+			part = &xpc_partitions[partid];
+			if (part->act_state != XPC_P_INACTIVE) {
+				active_part_count++;
+
+				XPC_DEACTIVATE_PARTITION(part, xpcUnloading);
+			}
+		}
+
+		if (active_part_count) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout(0.3 * HZ);
+			set_current_state(TASK_RUNNING);
+		}
+
+	} while (active_part_count > 0);
+
+
+	/* close down protections for IPI operations */
+	xpc_restrict_IPI_ops();
+
+
+	/* clear the interface to XPC's functions */
+	xpc_clear_interface();
+
+	if (xpc_sysctl) {
+		unregister_sysctl_table(xpc_sysctl);
+	}
+}
+
+
+int __init
+xpc_init(void)
+{
+	int ret;
+	partid_t partid;
+	struct xpc_partition *part;
+	pid_t pid;
+
+
+	/*
+	 * xpc_remote_copy_buffer is used as a temporary buffer for bte_copy'ng
+	 * both a partition's reserved page and its XPC variables. Its size was
+	 * based on the size of a reserved page. So we need to ensure that the
+	 * XPC variables will fit as well.
+	 */
+	if (XPC_VARS_ALIGNED_SIZE > XPC_RSVD_PAGE_ALIGNED_SIZE) {
+		dev_err(xpc_part, "xpc_remote_copy_buffer is not big enough\n");
+		return -EPERM;
+	}
+	DBUG_ON((u64) xpc_remote_copy_buffer !=
+				L1_CACHE_ALIGN((u64) xpc_remote_copy_buffer));
+
+	snprintf(xpc_part->bus_id, BUS_ID_SIZE, "part");
+	snprintf(xpc_chan->bus_id, BUS_ID_SIZE, "chan");
+
+	xpc_sysctl = register_sysctl_table(xpc_sys_dir, 1);
+
+	/*
+	 * The first few fields of each entry of xpc_partitions[] need to
+	 * be initialized now so that calls to xpc_connect() and
+	 * xpc_disconnect() can be made prior to the activation of any remote
+	 * partition. NOTE THAT NONE OF THE OTHER FIELDS BELONGING TO THESE
+	 * ENTRIES ARE MEANINGFUL UNTIL AFTER AN ENTRY'S CORRESPONDING
+	 * PARTITION HAS BEEN ACTIVATED.
+	 */
+	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+		part = &xpc_partitions[partid];
+
+		DBUG_ON((u64) part != L1_CACHE_ALIGN((u64) part));
+
+		part->act_IRQ_rcvd = 0;
+		spin_lock_init(&part->act_lock);
+		part->act_state = XPC_P_INACTIVE;
+		XPC_SET_REASON(part, 0, 0);
+		part->setup_state = XPC_P_UNSET;
+		init_waitqueue_head(&part->teardown_wq);
+		atomic_set(&part->references, 0);
+	}
+
+	/*
+	 * Open up protections for IPI operations (and AMO operations on
+	 * Shub 1.1 systems).
+	 */
+	xpc_allow_IPI_ops();
+
+	/*
+	 * Interrupts being processed will increment this atomic variable and
+	 * awaken the heartbeat thread which will process the interrupts.
+	 */
+	atomic_set(&xpc_act_IRQ_rcvd, 0);
+
+	/*
+	 * This is safe to do before the xpc_hb_checker thread has started
+	 * because the handler releases a wait queue.  If an interrupt is
+	 * received before the thread is waiting, it will not go to sleep,
+	 * but rather immediately process the interrupt.
+	 */
+	ret = request_irq(SGI_XPC_ACTIVATE, xpc_act_IRQ_handler, 0,
+							"xpc hb", NULL);
+	if (ret != 0) {
+		dev_err(xpc_part, "can't register ACTIVATE IRQ handler, "
+			"errno=%d\n", -ret);
+
+		xpc_restrict_IPI_ops();
+
+		if (xpc_sysctl) {
+			unregister_sysctl_table(xpc_sysctl);
+		}
+		return -EBUSY;
+	}
+
+	/*
+	 * Fill the partition reserved page with the information needed by
+	 * other partitions to discover we are alive and establish initial
+	 * communications.
+	 */
+	xpc_rsvd_page = xpc_rsvd_page_init();
+	if (xpc_rsvd_page == NULL) {
+		dev_err(xpc_part, "could not setup our reserved page\n");
+
+		free_irq(SGI_XPC_ACTIVATE, NULL);
+		xpc_restrict_IPI_ops();
+
+		if (xpc_sysctl) {
+			unregister_sysctl_table(xpc_sysctl);
+		}
+		return -EBUSY;
+	}
+
+
+	/*
+	 * Set the beating to other partitions into motion.  This is
+	 * the last requirement for other partitions' discovery to
+	 * initiate communications with us.
+	 */
+	init_timer(&xpc_hb_timer);
+	xpc_hb_timer.function = xpc_hb_beater;
+	xpc_hb_beater(0);
+
+
+	/*
+	 * The real work-horse behind xpc.  This processes incoming
+	 * interrupts and monitors remote heartbeats.
+	 */
+	pid = kernel_thread(xpc_hb_checker, NULL, 0);
+	if (pid < 0) {
+		dev_err(xpc_part, "failed while forking hb check thread\n");
+
+		/* indicate to others that our reserved page is uninitialized */
+		xpc_rsvd_page->vars_pa = 0;
+
+		del_timer_sync(&xpc_hb_timer);
+		free_irq(SGI_XPC_ACTIVATE, NULL);
+		xpc_restrict_IPI_ops();
+
+		if (xpc_sysctl) {
+			unregister_sysctl_table(xpc_sysctl);
+		}
+		return -EBUSY;
+	}
+
+
+	/*
+	 * Startup a thread that will attempt to discover other partitions to
+	 * activate based on info provided by SAL. This new thread is short
+	 * lived and will exit once discovery is complete.
+	 */
+	pid = kernel_thread(xpc_initiate_discovery, NULL, 0);
+	if (pid < 0) {
+		dev_err(xpc_part, "failed while forking discovery thread\n");
+
+		/* mark this new thread as a non-starter */
+		up(&xpc_discovery_exited);
+
+		xpc_do_exit();
+		return -EBUSY;
+	}
+
+
+	/* set the interface to point at XPC's functions */
+	xpc_set_interface(xpc_initiate_connect, xpc_initiate_disconnect,
+			  xpc_initiate_allocate, xpc_initiate_send,
+			  xpc_initiate_send_notify, xpc_initiate_received,
+			  xpc_initiate_partid_to_nasids);
+
+	return 0;
+}
+module_init(xpc_init);
+
+
+void __exit
+xpc_exit(void)
+{
+	xpc_do_exit();
+}
+module_exit(xpc_exit);
+
+
+MODULE_AUTHOR("Silicon Graphics, Inc.");
+MODULE_DESCRIPTION("Cross Partition Communication (XPC) support");
+MODULE_LICENSE("GPL");
+
+module_param(xpc_hb_interval, int, 0);
+MODULE_PARM_DESC(xpc_hb_interval, "Number of seconds between "
+		"heartbeat increments.");
+
+module_param(xpc_hb_check_interval, int, 0);
+MODULE_PARM_DESC(xpc_hb_check_interval, "Number of seconds between "
+		"heartbeat checks.");
+

arch/ia64/sn/kernel/xpc_partition.c

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2004-2005 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+
+
+/*
+ * Cross Partition Communication (XPC) partition support.
+ *
+ *	This is the part of XPC that detects the presence/absence of
+ *	other partitions. It provides a heartbeat and monitors the
+ *	heartbeats of other partitions.
+ *
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/sysctl.h>
+#include <linux/cache.h>
+#include <linux/mmzone.h>
+#include <linux/nodemask.h>
+#include <asm/sn/bte.h>
+#include <asm/sn/intr.h>
+#include <asm/sn/sn_sal.h>
+#include <asm/sn/nodepda.h>
+#include <asm/sn/addrs.h>
+#include "xpc.h"
+
+
+/* XPC is exiting flag */
+int xpc_exiting;
+
+
+/* SH_IPI_ACCESS shub register value on startup */
+static u64 xpc_sh1_IPI_access;
+static u64 xpc_sh2_IPI_access0;
+static u64 xpc_sh2_IPI_access1;
+static u64 xpc_sh2_IPI_access2;
+static u64 xpc_sh2_IPI_access3;
+
+
+/* original protection values for each node */
+u64 xpc_prot_vec[MAX_COMPACT_NODES];
+
+
+/* this partition's reserved page */
+struct xpc_rsvd_page *xpc_rsvd_page;
+
+/* this partition's XPC variables (within the reserved page) */
+struct xpc_vars *xpc_vars;
+struct xpc_vars_part *xpc_vars_part;
+
+
+/*
+ * For performance reasons, each entry of xpc_partitions[] is cacheline
+ * aligned. And xpc_partitions[] is padded with an additional entry at the
+ * end so that the last legitimate entry doesn't share its cacheline with
+ * another variable.
+ */
+struct xpc_partition xpc_partitions[XP_MAX_PARTITIONS + 1];
+
+
+/*
+ * Generic buffer used to store a local copy of the remote partitions
+ * reserved page or XPC variables.
+ *
+ * xpc_discovery runs only once and is a seperate thread that is
+ * very likely going to be processing in parallel with receiving
+ * interrupts.
+ */
+char ____cacheline_aligned
+		xpc_remote_copy_buffer[XPC_RSVD_PAGE_ALIGNED_SIZE];
+
+
+/* systune related variables */
+int xpc_hb_interval = XPC_HB_DEFAULT_INTERVAL;
+int xpc_hb_check_interval = XPC_HB_CHECK_DEFAULT_TIMEOUT;
+
+
+/*
+ * Given a nasid, get the physical address of the  partition's reserved page
+ * for that nasid. This function returns 0 on any error.
+ */
+static u64
+xpc_get_rsvd_page_pa(int nasid, u64 buf, u64 buf_size)
+{
+	bte_result_t bte_res;
+	s64 status;
+	u64 cookie = 0;
+	u64 rp_pa = nasid;	/* seed with nasid */
+	u64 len = 0;
+
+
+	while (1) {
+
+		status = sn_partition_reserved_page_pa(buf, &cookie, &rp_pa,
+								&len);
+
+		dev_dbg(xpc_part, "SAL returned with status=%li, cookie="
+			"0x%016lx, address=0x%016lx, len=0x%016lx\n",
+			status, cookie, rp_pa, len);
+
+		if (status != SALRET_MORE_PASSES) {
+			break;
+		}
+
+		if (len > buf_size) {
+			dev_err(xpc_part, "len (=0x%016lx) > buf_size\n", len);
+			status = SALRET_ERROR;
+			break;
+		}
+
+		bte_res = xp_bte_copy(rp_pa, ia64_tpa(buf), buf_size,
+					(BTE_NOTIFY | BTE_WACQUIRE), NULL);
+		if (bte_res != BTE_SUCCESS) {
+			dev_dbg(xpc_part, "xp_bte_copy failed %i\n", bte_res);
+			status = SALRET_ERROR;
+			break;
+		}
+	}
+
+	if (status != SALRET_OK) {
+		rp_pa = 0;
+	}
+	dev_dbg(xpc_part, "reserved page at phys address 0x%016lx\n", rp_pa);
+	return rp_pa;
+}
+
+
+/*
+ * Fill the partition reserved page with the information needed by
+ * other partitions to discover we are alive and establish initial
+ * communications.
+ */
+struct xpc_rsvd_page *
+xpc_rsvd_page_init(void)
+{
+	struct xpc_rsvd_page *rp;
+	AMO_t *amos_page;
+	u64 rp_pa, next_cl, nasid_array = 0;
+	int i, ret;
+
+
+	/* get the local reserved page's address */
+
+	rp_pa = xpc_get_rsvd_page_pa(cnodeid_to_nasid(0),
+					(u64) xpc_remote_copy_buffer,
+						XPC_RSVD_PAGE_ALIGNED_SIZE);
+	if (rp_pa == 0) {
+		dev_err(xpc_part, "SAL failed to locate the reserved page\n");
+		return NULL;
+	}
+	rp = (struct xpc_rsvd_page *) __va(rp_pa);
+
+	if (rp->partid != sn_partition_id) {
+		dev_err(xpc_part, "the reserved page's partid of %d should be "
+			"%d\n", rp->partid, sn_partition_id);
+		return NULL;
+	}
+
+	rp->version = XPC_RP_VERSION;
+
+	/*
+	 * Place the XPC variables on the cache line following the
+	 * reserved page structure.
+	 */
+	next_cl = (u64) rp + XPC_RSVD_PAGE_ALIGNED_SIZE;
+	xpc_vars = (struct xpc_vars *) next_cl;
+
+	/*
+	 * Before clearing xpc_vars, see if a page of AMOs had been previously
+	 * allocated. If not we'll need to allocate one and set permissions
+	 * so that cross-partition AMOs are allowed.
+	 *
+	 * The allocated AMO page needs MCA reporting to remain disabled after
+	 * XPC has unloaded.  To make this work, we keep a copy of the pointer
+	 * to this page (i.e., amos_page) in the struct xpc_vars structure,
+	 * which is pointed to by the reserved page, and re-use that saved copy
+	 * on subsequent loads of XPC. This AMO page is never freed, and its
+	 * memory protections are never restricted.
+	 */
+	if ((amos_page = xpc_vars->amos_page) == NULL) {
+		amos_page = (AMO_t *) mspec_kalloc_page(0);
+		if (amos_page == NULL) {
+			dev_err(xpc_part, "can't allocate page of AMOs\n");
+			return NULL;
+		}
+
+		/*
+		 * Open up AMO-R/W to cpu.  This is done for Shub 1.1 systems
+		 * when xpc_allow_IPI_ops() is called via xpc_hb_init().
+		 */
+		if (!enable_shub_wars_1_1()) {
+			ret = sn_change_memprotect(ia64_tpa((u64) amos_page),
+					PAGE_SIZE, SN_MEMPROT_ACCESS_CLASS_1,
+					&nasid_array);
+			if (ret != 0) {
+				dev_err(xpc_part, "can't change memory "
+					"protections\n");
+				mspec_kfree_page((unsigned long) amos_page);
+				return NULL;
+			}
+		}
+	}
+
+	memset(xpc_vars, 0, sizeof(struct xpc_vars));
+
+	/*
+	 * Place the XPC per partition specific variables on the cache line
+	 * following the XPC variables structure.
+	 */
+	next_cl += XPC_VARS_ALIGNED_SIZE;
+	memset((u64 *) next_cl, 0, sizeof(struct xpc_vars_part) *
+							XP_MAX_PARTITIONS);
+	xpc_vars_part = (struct xpc_vars_part *) next_cl;
+	xpc_vars->vars_part_pa = __pa(next_cl);
+
+	xpc_vars->version = XPC_V_VERSION;
+	xpc_vars->act_nasid = cpuid_to_nasid(0);
+	xpc_vars->act_phys_cpuid = cpu_physical_id(0);
+	xpc_vars->amos_page = amos_page;  /* save for next load of XPC */
+
+
+	/*
+	 * Initialize the activation related AMO variables.
+	 */
+	xpc_vars->act_amos = xpc_IPI_init(XP_MAX_PARTITIONS);
+	for (i = 1; i < XP_NASID_MASK_WORDS; i++) {
+		xpc_IPI_init(i + XP_MAX_PARTITIONS);
+	}
+	/* export AMO page's physical address to other partitions */
+	xpc_vars->amos_page_pa = ia64_tpa((u64) xpc_vars->amos_page);
+
+	/*
+	 * This signifies to the remote partition that our reserved
+	 * page is initialized.
+	 */
+	(volatile u64) rp->vars_pa = __pa(xpc_vars);
+
+	return rp;
+}
+
+
+/*
+ * Change protections to allow IPI operations (and AMO operations on
+ * Shub 1.1 systems).
+ */
+void
+xpc_allow_IPI_ops(void)
+{
+	int node;
+	int nasid;
+
+
+	// >>> Change SH_IPI_ACCESS code to use SAL call once it is available.
+
+	if (is_shub2()) {
+		xpc_sh2_IPI_access0 =
+			(u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS0));
+		xpc_sh2_IPI_access1 =
+			(u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS1));
+		xpc_sh2_IPI_access2 =
+			(u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS2));
+		xpc_sh2_IPI_access3 =
+			(u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH2_IPI_ACCESS3));
+
+		for_each_online_node(node) {
+			nasid = cnodeid_to_nasid(node);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
+								-1UL);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
+								-1UL);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
+								-1UL);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
+								-1UL);
+		}
+
+	} else {
+		xpc_sh1_IPI_access =
+			(u64) HUB_L((u64 *) LOCAL_MMR_ADDR(SH1_IPI_ACCESS));
+
+		for_each_online_node(node) {
+			nasid = cnodeid_to_nasid(node);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
+								-1UL);
+
+			/*
+			 * Since the BIST collides with memory operations on
+			 * SHUB 1.1 sn_change_memprotect() cannot be used.
+			 */
+			if (enable_shub_wars_1_1()) {
+				/* open up everything */
+				xpc_prot_vec[node] = (u64) HUB_L((u64 *)
+						GLOBAL_MMR_ADDR(nasid,
+						SH1_MD_DQLP_MMR_DIR_PRIVEC0));
+				HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
+						SH1_MD_DQLP_MMR_DIR_PRIVEC0),
+								-1UL);
+				HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
+						SH1_MD_DQRP_MMR_DIR_PRIVEC0),
+								-1UL);
+			}
+		}
+	}
+}
+
+
+/*
+ * Restrict protections to disallow IPI operations (and AMO operations on
+ * Shub 1.1 systems).
+ */
+void
+xpc_restrict_IPI_ops(void)
+{
+	int node;
+	int nasid;
+
+
+	// >>> Change SH_IPI_ACCESS code to use SAL call once it is available.
+
+	if (is_shub2()) {
+
+		for_each_online_node(node) {
+			nasid = cnodeid_to_nasid(node);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
+							xpc_sh2_IPI_access0);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
+							xpc_sh2_IPI_access1);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
+							xpc_sh2_IPI_access2);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
+							xpc_sh2_IPI_access3);
+		}
+
+	} else {
+
+		for_each_online_node(node) {
+			nasid = cnodeid_to_nasid(node);
+			HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
+							xpc_sh1_IPI_access);
+
+			if (enable_shub_wars_1_1()) {
+				HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
+						SH1_MD_DQLP_MMR_DIR_PRIVEC0),
+							xpc_prot_vec[node]);
+				HUB_S((u64 *) GLOBAL_MMR_ADDR(nasid,
+						SH1_MD_DQRP_MMR_DIR_PRIVEC0),
+							xpc_prot_vec[node]);
+			}
+		}
+	}
+}
+
+
+/*
+ * At periodic intervals, scan through all active partitions and ensure
+ * their heartbeat is still active.  If not, the partition is deactivated.
+ */
+void
+xpc_check_remote_hb(void)
+{
+	struct xpc_vars *remote_vars;
+	struct xpc_partition *part;
+	partid_t partid;
+	bte_result_t bres;
+
+
+	remote_vars = (struct xpc_vars *) xpc_remote_copy_buffer;
+
+	for (partid = 1; partid < XP_MAX_PARTITIONS; partid++) {
+		if (partid == sn_partition_id) {
+			continue;
+		}
+
+		part = &xpc_partitions[partid];
+
+		if (part->act_state == XPC_P_INACTIVE ||
+				part->act_state == XPC_P_DEACTIVATING) {
+			continue;
+		}
+
+		/* pull the remote_hb cache line */
+		bres = xp_bte_copy(part->remote_vars_pa,
+					ia64_tpa((u64) remote_vars),
+					XPC_VARS_ALIGNED_SIZE,
+					(BTE_NOTIFY | BTE_WACQUIRE), NULL);
+		if (bres != BTE_SUCCESS) {
+			XPC_DEACTIVATE_PARTITION(part,
+						xpc_map_bte_errors(bres));
+			continue;
+		}
+
+		dev_dbg(xpc_part, "partid = %d, heartbeat = %ld, last_heartbeat"
+			" = %ld, kdb_status = %ld, HB_mask = 0x%lx\n", partid,
+			remote_vars->heartbeat, part->last_heartbeat,
+			remote_vars->kdb_status,
+			remote_vars->heartbeating_to_mask);
+
+		if (((remote_vars->heartbeat == part->last_heartbeat) &&
+			(remote_vars->kdb_status == 0)) ||
+			     !XPC_HB_ALLOWED(sn_partition_id, remote_vars)) {
+
+			XPC_DEACTIVATE_PARTITION(part, xpcNoHeartbeat);
+			continue;
+		}
+
+		part->last_heartbeat = remote_vars->heartbeat;
+	}
+}
+
+
+/*
+ * Get a copy of the remote partition's rsvd page.
+ *
+ * remote_rp points to a buffer that is cacheline aligned for BTE copies and
+ * assumed to be of size XPC_RSVD_PAGE_ALIGNED_SIZE.
+ */
+static enum xpc_retval
+xpc_get_remote_rp(int nasid, u64 *discovered_nasids,
+		struct xpc_rsvd_page *remote_rp, u64 *remote_rsvd_page_pa)
+{
+	int bres, i;
+
+
+	/* get the reserved page's physical address */
+
+	*remote_rsvd_page_pa = xpc_get_rsvd_page_pa(nasid, (u64) remote_rp,
+						XPC_RSVD_PAGE_ALIGNED_SIZE);
+	if (*remote_rsvd_page_pa == 0) {
+		return xpcNoRsvdPageAddr;
+	}
+
+
+	/* pull over the reserved page structure */
+
+	bres = xp_bte_copy(*remote_rsvd_page_pa, ia64_tpa((u64) remote_rp),
+				XPC_RSVD_PAGE_ALIGNED_SIZE,
+				(BTE_NOTIFY | BTE_WACQUIRE), NULL);
+	if (bres != BTE_SUCCESS) {
+		return xpc_map_bte_errors(bres);
+	}
+
+
+	if (discovered_nasids != NULL) {
+		for (i = 0; i < XP_NASID_MASK_WORDS; i++) {
+			discovered_nasids[i] |= remote_rp->part_nasids[i];
+		}
+	}
+
+
+	/* check that the partid is for another partition */
+
+	if (remote_rp->partid < 1 ||
+				remote_rp->partid > (XP_MAX_PARTITIONS - 1)) {
+		return xpcInvalidPartid;
+	}
+
+	if (remote_rp->partid == sn_partition_id) {
+		return xpcLocalPartid;
+	}
+
+
+	if (XPC_VERSION_MAJOR(remote_rp->version) !=
+					XPC_VERSION_MAJOR(XPC_RP_VERSION)) {
+		return xpcBadVersion;
+	}
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Get a copy of the remote partition's XPC variables.
+ *
+ * remote_vars points to a buffer that is cacheline aligned for BTE copies and
+ * assumed to be of size XPC_VARS_ALIGNED_SIZE.
+ */
+static enum xpc_retval
+xpc_get_remote_vars(u64 remote_vars_pa, struct xpc_vars *remote_vars)
+{
+	int bres;
+
+
+	if (remote_vars_pa == 0) {
+		return xpcVarsNotSet;
+	}
+
+
+	/* pull over the cross partition variables */
+
+	bres = xp_bte_copy(remote_vars_pa, ia64_tpa((u64) remote_vars),
+				XPC_VARS_ALIGNED_SIZE,
+				(BTE_NOTIFY | BTE_WACQUIRE), NULL);
+	if (bres != BTE_SUCCESS) {
+		return xpc_map_bte_errors(bres);
+	}
+
+	if (XPC_VERSION_MAJOR(remote_vars->version) !=
+					XPC_VERSION_MAJOR(XPC_V_VERSION)) {
+		return xpcBadVersion;
+	}
+
+	return xpcSuccess;
+}
+
+
+/*
+ * Prior code has determine the nasid which generated an IPI.  Inspect
+ * that nasid to determine if its partition needs to be activated or
+ * deactivated.
+ *
+ * A partition is consider "awaiting activation" if our partition
+ * flags indicate it is not active and it has a heartbeat.  A
+ * partition is considered "awaiting deactivation" if our partition
+ * flags indicate it is active but it has no heartbeat or it is not
+ * sending its heartbeat to us.
+ *
+ * To determine the heartbeat, the remote nasid must have a properly
+ * initialized reserved page.
+ */
+static void
+xpc_identify_act_IRQ_req(int nasid)
+{
+	struct xpc_rsvd_page *remote_rp;
+	struct xpc_vars *remote_vars;
+	u64 remote_rsvd_page_pa;
+	u64 remote_vars_pa;
+	partid_t partid;
+	struct xpc_partition *part;
+	enum xpc_retval ret;
+
+
+	/* pull over the reserved page structure */
+
+	remote_rp = (struct xpc_rsvd_page *) xpc_remote_copy_buffer;
+
+	ret = xpc_get_remote_rp(nasid, NULL, remote_rp, &remote_rsvd_page_pa);
+	if (ret != xpcSuccess) {
+		dev_warn(xpc_part, "unable to get reserved page from nasid %d, "
+			"which sent interrupt, reason=%d\n", nasid, ret);
+		return;
+	}
+
+	remote_vars_pa = remote_rp->vars_pa;
+	partid = remote_rp->partid;
+	part = &xpc_partitions[partid];
+
+
+	/* pull over the cross partition variables */
+
+	remote_vars = (struct xpc_vars *) xpc_remote_copy_buffer;
+
+	ret = xpc_get_remote_vars(remote_vars_pa, remote_vars);
+	if (ret != xpcSuccess) {
+
+		dev_warn(xpc_part, "unable to get XPC variables from nasid %d, "
+			"which sent interrupt, reason=%d\n", nasid, ret);
+
+		XPC_DEACTIVATE_PARTITION(part, ret);
+		return;
+	}
+
+
+	part->act_IRQ_rcvd++;
+
+	dev_dbg(xpc_part, "partid for nasid %d is %d; IRQs = %d; HB = "
+		"%ld:0x%lx\n", (int) nasid, (int) partid, part->act_IRQ_rcvd,
+		remote_vars->heartbeat, remote_vars->heartbeating_to_mask);
+
+
+	if (part->act_state == XPC_P_INACTIVE) {
+
+		part->remote_rp_pa = remote_rsvd_page_pa;
+		dev_dbg(xpc_part, "  remote_rp_pa = 0x%016lx\n",
+			part->remote_rp_pa);
+
+		part->remote_vars_pa = remote_vars_pa;
+		dev_dbg(xpc_part, "  remote_vars_pa = 0x%016lx\n",
+			part->remote_vars_pa);
+
+		part->last_heartbeat = remote_vars->heartbeat;
+		dev_dbg(xpc_part, "  last_heartbeat = 0x%016lx\n",
+			part->last_heartbeat);
+
+		part->remote_vars_part_pa = remote_vars->vars_part_pa;
+		dev_dbg(xpc_part, "  remote_vars_part_pa = 0x%016lx\n",
+			part->remote_vars_part_pa);
+
+		part->remote_act_nasid = remote_vars->act_nasid;
+		dev_dbg(xpc_part, "  remote_act_nasid = 0x%x\n",
+			part->remote_act_nasid);
+
+		part->remote_act_phys_cpuid = remote_vars->act_phys_cpuid;
+		dev_dbg(xpc_part, "  remote_act_phys_cpuid = 0x%x\n",
+			part->remote_act_phys_cpuid);
+
+		part->remote_amos_page_pa = remote_vars->amos_page_pa;
+		dev_dbg(xpc_part, "  remote_amos_page_pa = 0x%lx\n",
+			part->remote_amos_page_pa);
+
+		xpc_activate_partition(part);
+
+	} else if (part->remote_amos_page_pa != remote_vars->amos_page_pa ||
+			!XPC_HB_ALLOWED(sn_partition_id, remote_vars)) {
+
+		part->reactivate_nasid = nasid;
+		XPC_DEACTIVATE_PARTITION(part, xpcReactivating);
+	}
+}
+
+
+/*
+ * Loop through the activation AMO variables and process any bits
+ * which are set.  Each bit indicates a nasid sending a partition
+ * activation or deactivation request.
+ *
+ * Return #of IRQs detected.
+ */
+int
+xpc_identify_act_IRQ_sender(void)
+{
+	int word, bit;
+	u64 nasid_mask;
+	u64 nasid;			/* remote nasid */
+	int n_IRQs_detected = 0;
+	AMO_t *act_amos;
+	struct xpc_rsvd_page *rp = (struct xpc_rsvd_page *) xpc_rsvd_page;
+
+
+	act_amos = xpc_vars->act_amos;
+
+
+	/* scan through act AMO variable looking for non-zero entries */
+	for (word = 0; word < XP_NASID_MASK_WORDS; word++) {
+
+		nasid_mask = xpc_IPI_receive(&act_amos[word]);
+		if (nasid_mask == 0) {
+			/* no IRQs from nasids in this variable */
+			continue;
+		}
+
+		dev_dbg(xpc_part, "AMO[%d] gave back 0x%lx\n", word,
+			nasid_mask);
+
+
+		/*
+		 * If this nasid has been added to the machine since
+		 * our partition was reset, this will retain the
+		 * remote nasid in our reserved pages machine mask.
+		 * This is used in the event of module reload.
+		 */
+		rp->mach_nasids[word] |= nasid_mask;
+
+
+		/* locate the nasid(s) which sent interrupts */
+
+		for (bit = 0; bit < (8 * sizeof(u64)); bit++) {
+			if (nasid_mask & (1UL << bit)) {
+				n_IRQs_detected++;
+				nasid = XPC_NASID_FROM_W_B(word, bit);
+				dev_dbg(xpc_part, "interrupt from nasid %ld\n",
+					nasid);
+				xpc_identify_act_IRQ_req(nasid);
+			}
+		}
+	}
+	return n_IRQs_detected;
+}
+
+
+/*
+ * Mark specified partition as active.
+ */
+enum xpc_retval
+xpc_mark_partition_active(struct xpc_partition *part)
+{
+	unsigned long irq_flags;
+	enum xpc_retval ret;
+
+
+	dev_dbg(xpc_part, "setting partition %d to ACTIVE\n", XPC_PARTID(part));
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+	if (part->act_state == XPC_P_ACTIVATING) {
+		part->act_state = XPC_P_ACTIVE;
+		ret = xpcSuccess;
+	} else {
+		DBUG_ON(part->reason == xpcSuccess);
+		ret = part->reason;
+	}
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+
+	return ret;
+}
+
+
+/*
+ * Notify XPC that the partition is down.
+ */
+void
+xpc_deactivate_partition(const int line, struct xpc_partition *part,
+				enum xpc_retval reason)
+{
+	unsigned long irq_flags;
+	partid_t partid = XPC_PARTID(part);
+
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+
+	if (part->act_state == XPC_P_INACTIVE) {
+		XPC_SET_REASON(part, reason, line);
+		spin_unlock_irqrestore(&part->act_lock, irq_flags);
+		if (reason == xpcReactivating) {
+			/* we interrupt ourselves to reactivate partition */
+			xpc_IPI_send_reactivate(part);
+		}
+		return;
+	}
+	if (part->act_state == XPC_P_DEACTIVATING) {
+		if ((part->reason == xpcUnloading && reason != xpcUnloading) ||
+					reason == xpcReactivating) {
+			XPC_SET_REASON(part, reason, line);
+		}
+		spin_unlock_irqrestore(&part->act_lock, irq_flags);
+		return;
+	}
+
+	part->act_state = XPC_P_DEACTIVATING;
+	XPC_SET_REASON(part, reason, line);
+
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+
+	XPC_DISALLOW_HB(partid, xpc_vars);
+
+	dev_dbg(xpc_part, "bringing partition %d down, reason = %d\n", partid,
+		reason);
+
+	xpc_partition_down(part, reason);
+}
+
+
+/*
+ * Mark specified partition as active.
+ */
+void
+xpc_mark_partition_inactive(struct xpc_partition *part)
+{
+	unsigned long irq_flags;
+
+
+	dev_dbg(xpc_part, "setting partition %d to INACTIVE\n",
+		XPC_PARTID(part));
+
+	spin_lock_irqsave(&part->act_lock, irq_flags);
+	part->act_state = XPC_P_INACTIVE;
+	spin_unlock_irqrestore(&part->act_lock, irq_flags);
+	part->remote_rp_pa = 0;
+}
+
+
+/*
+ * SAL has provided a partition and machine mask.  The partition mask
+ * contains a bit for each even nasid in our partition.  The machine
+ * mask contains a bit for each even nasid in the entire machine.
+ *
+ * Using those two bit arrays, we can determine which nasids are
+ * known in the machine.  Each should also have a reserved page
+ * initialized if they are available for partitioning.
+ */
+void
+xpc_discovery(void)
+{
+	void *remote_rp_base;
+	struct xpc_rsvd_page *remote_rp;
+	struct xpc_vars *remote_vars;
+	u64 remote_rsvd_page_pa;
+	u64 remote_vars_pa;
+	int region;
+	int max_regions;
+	int nasid;
+	struct xpc_rsvd_page *rp;
+	partid_t partid;
+	struct xpc_partition *part;
+	u64 *discovered_nasids;
+	enum xpc_retval ret;
+
+
+	remote_rp = xpc_kmalloc_cacheline_aligned(XPC_RSVD_PAGE_ALIGNED_SIZE,
+						GFP_KERNEL, &remote_rp_base);
+	if (remote_rp == NULL) {
+		return;
+	}
+	remote_vars = (struct xpc_vars *) remote_rp;
+
+
+	discovered_nasids = kmalloc(sizeof(u64) * XP_NASID_MASK_WORDS,
+							GFP_KERNEL);
+	if (discovered_nasids == NULL) {
+		kfree(remote_rp_base);
+		return;
+	}
+	memset(discovered_nasids, 0, sizeof(u64) * XP_NASID_MASK_WORDS);
+
+	rp = (struct xpc_rsvd_page *) xpc_rsvd_page;
+
+	/*
+	 * The term 'region' in this context refers to the minimum number of
+	 * nodes that can comprise an access protection grouping. The access
+	 * protection is in regards to memory, IOI and IPI.
+	 */
+//>>> move the next two #defines into either include/asm-ia64/sn/arch.h or
+//>>> include/asm-ia64/sn/addrs.h
+#define SH1_MAX_REGIONS		64
+#define SH2_MAX_REGIONS		256
+	max_regions = is_shub2() ? SH2_MAX_REGIONS : SH1_MAX_REGIONS;
+
+	for (region = 0; region < max_regions; region++) {
+
+		if ((volatile int) xpc_exiting) {
+			break;
+		}
+
+		dev_dbg(xpc_part, "searching region %d\n", region);
+
+		for (nasid = (region * sn_region_size * 2);
+		     nasid < ((region + 1) * sn_region_size * 2);
+		     nasid += 2) {
+
+			if ((volatile int) xpc_exiting) {
+				break;
+			}
+
+			dev_dbg(xpc_part, "checking nasid %d\n", nasid);
+
+
+			if (XPC_NASID_IN_ARRAY(nasid, rp->part_nasids)) {
+				dev_dbg(xpc_part, "PROM indicates Nasid %d is "
+					"part of the local partition; skipping "
+					"region\n", nasid);
+				break;
+			}
+
+			if (!(XPC_NASID_IN_ARRAY(nasid, rp->mach_nasids))) {
+				dev_dbg(xpc_part, "PROM indicates Nasid %d was "
+					"not on Numa-Link network at reset\n",
+					nasid);
+				continue;
+			}
+
+			if (XPC_NASID_IN_ARRAY(nasid, discovered_nasids)) {
+				dev_dbg(xpc_part, "Nasid %d is part of a "
+					"partition which was previously "
+					"discovered\n", nasid);
+				continue;
+			}
+
+
+			/* pull over the reserved page structure */
+
+			ret = xpc_get_remote_rp(nasid, discovered_nasids,
+					      remote_rp, &remote_rsvd_page_pa);
+			if (ret != xpcSuccess) {
+				dev_dbg(xpc_part, "unable to get reserved page "
+					"from nasid %d, reason=%d\n", nasid,
+					ret);
+
+				if (ret == xpcLocalPartid) {
+					break;
+				}
+				continue;
+			}
+
+			remote_vars_pa = remote_rp->vars_pa;
+
+			partid = remote_rp->partid;
+			part = &xpc_partitions[partid];
+
+
+			/* pull over the cross partition variables */
+
+			ret = xpc_get_remote_vars(remote_vars_pa, remote_vars);
+			if (ret != xpcSuccess) {
+				dev_dbg(xpc_part, "unable to get XPC variables "
+					"from nasid %d, reason=%d\n", nasid,
+					ret);
+
+				XPC_DEACTIVATE_PARTITION(part, ret);
+				continue;
+			}
+
+			if (part->act_state != XPC_P_INACTIVE) {
+				dev_dbg(xpc_part, "partition %d on nasid %d is "
+					"already activating\n", partid, nasid);
+				break;
+			}
+
+			/*
+			 * Register the remote partition's AMOs with SAL so it
+			 * can handle and cleanup errors within that address
+			 * range should the remote partition go down. We don't
+			 * unregister this range because it is difficult to
+			 * tell when outstanding writes to the remote partition
+			 * are finished and thus when it is thus safe to
+			 * unregister. This should not result in wasted space
+			 * in the SAL xp_addr_region table because we should
+			 * get the same page for remote_act_amos_pa after
+			 * module reloads and system reboots.
+			 */
+			if (sn_register_xp_addr_region(
+					    remote_vars->amos_page_pa,
+							PAGE_SIZE, 1) < 0) {
+				dev_dbg(xpc_part, "partition %d failed to "
+					"register xp_addr region 0x%016lx\n",
+					partid, remote_vars->amos_page_pa);
+
+				XPC_SET_REASON(part, xpcPhysAddrRegFailed,
+						__LINE__);
+				break;
+			}
+
+			/*
+			 * The remote nasid is valid and available.
+			 * Send an interrupt to that nasid to notify
+			 * it that we are ready to begin activation.
+			 */
+			dev_dbg(xpc_part, "sending an interrupt to AMO 0x%lx, "
+				"nasid %d, phys_cpuid 0x%x\n",
+				remote_vars->amos_page_pa,
+				remote_vars->act_nasid,
+				remote_vars->act_phys_cpuid);
+
+			xpc_IPI_send_activate(remote_vars);
+		}
+	}
+
+	kfree(discovered_nasids);
+	kfree(remote_rp_base);
+}
+
+
+/*
+ * Given a partid, get the nasids owned by that partition from the
+ * remote partitions reserved page.
+ */
+enum xpc_retval
+xpc_initiate_partid_to_nasids(partid_t partid, void *nasid_mask)
+{
+	struct xpc_partition *part;
+	u64 part_nasid_pa;
+	int bte_res;
+
+
+	part = &xpc_partitions[partid];
+	if (part->remote_rp_pa == 0) {
+		return xpcPartitionDown;
+	}
+
+	part_nasid_pa = part->remote_rp_pa +
+		(u64) &((struct xpc_rsvd_page *) 0)->part_nasids;
+
+	bte_res = xp_bte_copy(part_nasid_pa, ia64_tpa((u64) nasid_mask),
+				L1_CACHE_ALIGN(XP_NASID_MASK_BYTES),
+				(BTE_NOTIFY | BTE_WACQUIRE), NULL);
+
+	return xpc_map_bte_errors(bte_res);
+}
+