Drivers: hv: vmbus: Support handling messages on multiple CPUs

BugLink: http://bugs.launchpad.net/bugs/1541585

Starting with Windows 2012 R2, message inteerupts can be delivered
on any VCPU in the guest. Support this functionality.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit d81274aa)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/hv/hv.c

@@ -212,6 +212,8 @@ int hv_init(void)
 	       sizeof(int) * NR_CPUS);
 	memset(hv_context.event_dpc, 0,
 	       sizeof(void *) * NR_CPUS);
+	memset(hv_context.msg_dpc, 0,
+	       sizeof(void *) * NR_CPUS);
 	memset(hv_context.clk_evt, 0,
 	       sizeof(void *) * NR_CPUS);
 
@@ -423,6 +425,13 @@ int hv_synic_alloc(void)
 		}
 		tasklet_init(hv_context.event_dpc[cpu], vmbus_on_event, cpu);
 
+		hv_context.msg_dpc[cpu] = kmalloc(size, GFP_ATOMIC);
+		if (hv_context.msg_dpc[cpu] == NULL) {
+			pr_err("Unable to allocate event dpc\n");
+			goto err;
+		}
+		tasklet_init(hv_context.msg_dpc[cpu], vmbus_on_msg_dpc, cpu);
+
 		hv_context.clk_evt[cpu] = kzalloc(ced_size, GFP_ATOMIC);
 		if (hv_context.clk_evt[cpu] == NULL) {
 			pr_err("Unable to allocate clock event device\n");
@@ -464,6 +473,7 @@ int hv_synic_alloc(void)
 static void hv_synic_free_cpu(int cpu)
 {
 	kfree(hv_context.event_dpc[cpu]);
+	kfree(hv_context.msg_dpc[cpu]);
 	kfree(hv_context.clk_evt[cpu]);
 	if (hv_context.synic_event_page[cpu])
 		free_page((unsigned long)hv_context.synic_event_page[cpu]);

drivers/hv/hyperv_vmbus.h

@@ -443,10 +443,11 @@ struct hv_context {
 	u32 vp_index[NR_CPUS];
 	/*
 	 * Starting with win8, we can take channel interrupts on any CPU;
-	 * we will manage the tasklet that handles events on a per CPU
+	 * we will manage the tasklet that handles events messages on a per CPU
 	 * basis.
 	 */
 	struct tasklet_struct *event_dpc[NR_CPUS];
+	struct tasklet_struct *msg_dpc[NR_CPUS];
 	/*
 	 * To optimize the mapping of relid to channel, maintain
 	 * per-cpu list of the channels based on their CPU affinity.
@@ -669,6 +670,7 @@ int vmbus_post_msg(void *buffer, size_t buflen);
 void vmbus_set_event(struct vmbus_channel *channel);
 
 void vmbus_on_event(unsigned long data);
+void vmbus_on_msg_dpc(unsigned long data);
 
 int hv_kvp_init(struct hv_util_service *);
 void hv_kvp_deinit(void);

drivers/hv/vmbus_drv.c

@@ -45,7 +45,6 @@
 
 static struct acpi_device  *hv_acpi_dev;
 
-static struct tasklet_struct msg_dpc;
 static struct completion probe_event;
 
 
@@ -712,7 +711,7 @@ static void hv_process_timer_expiration(struct hv_message *msg, int cpu)
 	vmbus_signal_eom(msg);
 }
 
-static void vmbus_on_msg_dpc(unsigned long data)
+void vmbus_on_msg_dpc(unsigned long data)
 {
 	int cpu = smp_processor_id();
 	void *page_addr = hv_context.synic_message_page[cpu];
@@ -800,7 +799,7 @@ static void vmbus_isr(void)
 		if (msg->header.message_type == HVMSG_TIMER_EXPIRED)
 			hv_process_timer_expiration(msg, cpu);
 		else
-			tasklet_schedule(&msg_dpc);
+			tasklet_schedule(hv_context.msg_dpc[cpu]);
 	}
 }
 
@@ -824,8 +823,6 @@ static int vmbus_bus_init(void)
 		return ret;
 	}
 
-	tasklet_init(&msg_dpc, vmbus_on_msg_dpc, 0);
-
 	ret = bus_register(&hv_bus);
 	if (ret)
 		goto err_cleanup;
@@ -1321,7 +1318,8 @@ static void __exit vmbus_exit(void)
 	hv_synic_clockevents_cleanup();
 	vmbus_disconnect();
 	hv_remove_vmbus_irq();
-	tasklet_kill(&msg_dpc);
+	for_each_online_cpu(cpu)
+		tasklet_kill(hv_context.msg_dpc[cpu]);
 	vmbus_free_channels();
 	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
 		unregister_die_notifier(&hyperv_die_block);