[PATCH 09/11] KVM: Move kvm_guest_exit() after local_irq_enable()

Avi Kivity
2007-10-21T11:08:10Z

From: Laurent Vivier <Laurent.Vivier-6ktuUTfB/bM@public.gmane.org>

We need to make sure that the timer interrupt happens before we clear
PF_VCPU, so the accounting code actually sees guest mode.

http://lkml.org/lkml/2007/10/15/114

Signed-off-by: Laurent Vivier <Laurent.Vivier-6ktuUTfB/bM@public.gmane.org>
Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
drivers/kvm/kvm_main.c | 11 ++++++++++-
1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index af2d288..8c458f2 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -2054,12 +2054,21 @@ again:

kvm_x86_ops->run(vcpu, kvm_run);

- kvm_guest_exit();
vcpu->guest_mode = 0;
local_irq_enable();

++vcpu->stat.exits;

+ /*
+ * We must have an instruction between local_irq_enable() and
+ * kvm_guest_exit(), so the timer interrupt isn't delayed by
+ * the interrupt shadow. The stat.exits increment will do nicely.
+ * But we need to prevent reordering, hence this barrier():
+ */
+ barrier();
+
+ kvm_guest_exit();
+
preempt_enable();

/*