x86, cpu hotplug: Synchronise vcpu state earlier during cpu offline.

Needs to happen before non-idle VCPU is fully descheduled after CPU is
removed from cpu_online_map. Else sync_vcpu_execstate() doesn't work
properly.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 6321e56bfb38d3f06d87393f723718a2e1f3c66b..1ed5c9e73f19d587711f35f4dd32e9c11bb597bb 100644 (file)
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1442,7 +1442,8 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
 
     set_current(next);
 
-    if ( (per_cpu(curr_vcpu, cpu) == next) || is_idle_vcpu(next) )
+    if ( (per_cpu(curr_vcpu, cpu) == next) ||
+         (is_idle_vcpu(next) && cpu_online(cpu)) )
     {
         local_irq_enable();
     }

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 0fb829028e71a8af8ee70e281f151d0d3d0acc14..96db89fc54ee3a0ca392179bd3869da548d1901c 100644 (file)
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -997,17 +997,13 @@ static int __devinit do_boot_cpu(int apicid, int cpu)
        return boot_error;
 }
 
-static void idle_task_exit(void)
-{
-       /* Give up lazy state borrowed by this idle vcpu */
-       __sync_lazy_execstate();
-}
-
 void cpu_exit_clear(void)
 {
        int cpu = raw_smp_processor_id();
 
-       idle_task_exit();
+       /* Previous non-idle state should be synchronised already. */
+       if (__sync_lazy_execstate())
+               BUG();
 
        cpucount --;
        cpu_uninit();
@@ -1302,6 +1298,13 @@ int __cpu_disable(void)
 
        remove_siblinginfo(cpu);
 
+       /*
+        * If we are running the idle vcpu, sync last non-idle vcpu's state
+        * before changing cpu_online_map. If we are running non-idle vcpu,
+        * we will synchronously sync the state in context_switch() later.
+        */
+       __sync_lazy_execstate();
+
        /* It's now safe to remove this processor from the online map */
        cpu_clear(cpu, cpu_online_map);
        fixup_irqs();