[PATCH v4 3/3] xen/arm: don't try to re-register vcpu_info on cpu_hotplug.

[Stefano Stabellini]

Call disable_percpu_irq on CPU_DYING and enable_percpu_irq when the cpu
is coming up.

Signed-off-by: Stefano Stabellini <stefano.stabellini at eu.citrix.com>

---

Changes in v4:
- use goto
- call disable_percpu_irq on CPU_DYING

Changes in v3:
- call disable_percpu_irq on CPU_DYING
- call enable_percpu_irq even when VCPUOP_register_vcpu_info has already
been called

Changes in v2:
- better comment
---
 arch/arm/xen/enlighten.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 6c09cc4..1efa22b 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -93,6 +93,14 @@ static void xen_percpu_init(void)
 	int err;
 	int cpu = get_cpu();
 
+	/* 
+	 * VCPUOP_register_vcpu_info cannot be called twice for the same
+	 * vcpu, so if vcpu_info is already registered, just get out. This
+	 * can happen with cpu-hotplug.
+	 */
+	if (per_cpu(xen_vcpu, cpu) != NULL)
+		goto after_register_vcpu_info;
+
 	pr_info("Xen: initializing cpu%d\n", cpu);
 	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
 
@@ -103,6 +111,7 @@ static void xen_percpu_init(void)
 	BUG_ON(err);
 	per_cpu(xen_vcpu, cpu) = vcpup;
 
+after_register_vcpu_info:
 	enable_percpu_irq(xen_events_irq, 0);
 	put_cpu();
 }
@@ -131,6 +140,9 @@ static int xen_cpu_notification(struct notifier_block *self,
 	case CPU_STARTING:
 		xen_percpu_init();
 		break;
+	case CPU_DYING:
+		disable_percpu_irq(xen_events_irq);
+		break;
 	default:
 		break;
 	}
-- 
1.7.10.4