Commit 3a025de6 authored by Yi Sun's avatar Yi Sun Committed by Thomas Gleixner

x86/hyperv: Enable PV qspinlock for Hyper-V

Implement the required wait and kick callbacks to support PV spinlocks in
Hyper-V guests.

[ tglx: Document the requirement for disabling interrupts in the wait()
  	callback. Remove goto and unnecessary includes. Add prototype
	for hv_vcpu_is_preempted(). Adapted to pending paravirt changes. ]
Signed-off-by: default avatarYi Sun <yi.y.sun@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>
Cc: chao.p.peng@intel.com
Cc: chao.gao@intel.com
Cc: isaku.yamahata@intel.com
Cc: tianyu.lan@microsoft.com
Link: https://lkml.kernel.org/r/1538987374-51217-3-git-send-email-yi.y.sun@linux.intel.com
parent f726c462
......@@ -1385,6 +1385,11 @@
hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
If specified, z/VM IUCV HVC accepts connections
from listed z/VM user IDs only.
hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
which allow the hypervisor to 'idle' the
guest on lock contention.
keep_bootcon [KNL]
Do not unregister boot console at start. This is only
useful for debugging when something happens in the window
......
obj-y := hv_init.o mmu.o nested.o
obj-$(CONFIG_X86_64) += hv_apic.o
ifdef CONFIG_X86_64
obj-$(CONFIG_PARAVIRT_SPINLOCKS) += hv_spinlock.o
endif
// SPDX-License-Identifier: GPL-2.0
/*
* Hyper-V specific spinlock code.
*
* Copyright (C) 2018, Intel, Inc.
*
* Author : Yi Sun <yi.y.sun@intel.com>
*/
#define pr_fmt(fmt) "Hyper-V: " fmt
#include <linux/spinlock.h>
#include <asm/mshyperv.h>
#include <asm/paravirt.h>
#include <asm/apic.h>
static bool __initdata hv_pvspin = true;
static void hv_qlock_kick(int cpu)
{
apic->send_IPI(cpu, X86_PLATFORM_IPI_VECTOR);
}
static void hv_qlock_wait(u8 *byte, u8 val)
{
unsigned long msr_val;
unsigned long flags;
if (in_nmi())
return;
/*
* Reading HV_X64_MSR_GUEST_IDLE MSR tells the hypervisor that the
* vCPU can be put into 'idle' state. This 'idle' state is
* terminated by an IPI, usually from hv_qlock_kick(), even if
* interrupts are disabled on the vCPU.
*
* To prevent a race against the unlock path it is required to
* disable interrupts before accessing the HV_X64_MSR_GUEST_IDLE
* MSR. Otherwise, if the IPI from hv_qlock_kick() arrives between
* the lock value check and the rdmsrl() then the vCPU might be put
* into 'idle' state by the hypervisor and kept in that state for
* an unspecified amount of time.
*/
local_irq_save(flags);
/*
* Only issue the rdmsrl() when the lock state has not changed.
*/
if (READ_ONCE(*byte) == val)
rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val);
local_irq_restore(flags);
}
/*
* Hyper-V does not support this so far.
*/
bool hv_vcpu_is_preempted(int vcpu)
{
return false;
}
PV_CALLEE_SAVE_REGS_THUNK(hv_vcpu_is_preempted);
void __init hv_init_spinlocks(void)
{
if (!hv_pvspin || !apic ||
!(ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) ||
!(ms_hyperv.features & HV_X64_MSR_GUEST_IDLE_AVAILABLE)) {
pr_info("PV spinlocks disabled\n");
return;
}
pr_info("PV spinlocks enabled\n");
__pv_init_lock_hash();
pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
pv_ops.lock.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
pv_ops.lock.wait = hv_qlock_wait;
pv_ops.lock.kick = hv_qlock_kick;
pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(hv_vcpu_is_preempted);
}
static __init int hv_parse_nopvspin(char *arg)
{
hv_pvspin = false;
return 0;
}
early_param("hv_nopvspin", hv_parse_nopvspin);
......@@ -351,6 +351,8 @@ int hyperv_flush_guest_mapping(u64 as);
#ifdef CONFIG_X86_64
void hv_apic_init(void);
void __init hv_init_spinlocks(void);
bool hv_vcpu_is_preempted(int vcpu);
#else
static inline void hv_apic_init(void) {}
#endif
......
......@@ -199,6 +199,16 @@ static unsigned long hv_get_tsc_khz(void)
return freq / 1000;
}
#if defined(CONFIG_SMP) && IS_ENABLED(CONFIG_HYPERV)
static void __init hv_smp_prepare_boot_cpu(void)
{
native_smp_prepare_boot_cpu();
#if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS)
hv_init_spinlocks();
#endif
}
#endif
static void __init ms_hyperv_init_platform(void)
{
int hv_host_info_eax;
......@@ -303,6 +313,10 @@ static void __init ms_hyperv_init_platform(void)
if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
alloc_intr_gate(HYPERV_STIMER0_VECTOR,
hv_stimer0_callback_vector);
# ifdef CONFIG_SMP
smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
# endif
#endif
}
......
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