KVM: Fix reboot on Intel hosts

When we reboot, we disable vmx extensions or otherwise INIT gets blocked.
If a task on another cpu hits a vmx instruction, it will fault if vmx is
disabled.  We trap that to avoid a nasty oops and spin until the reboot
completes.

Problem is, we sleep with interrupts disabled.  This blocks smp_send_stop()
from running, and the reboot process halts.

Fix by enabling interrupts before spinning.

KVM-Stable-Tag.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d4853a5..5186e72 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1970,10 +1970,12 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
 
 asmlinkage void kvm_handle_fault_on_reboot(void)
 {
-       if (kvm_rebooting)
+       if (kvm_rebooting) {
                /* spin while reset goes on */
+               local_irq_enable();
                while (true)
                        ;
+       }
        /* Fault while not rebooting.  We want the trace. */
        BUG();
 }