KVM: Add "exiting guest mode" state

Currently we keep track of only two states: guest mode and host
mode.  This patch adds an "exiting guest mode" state that tells
us that an IPI will happen soon, so unless we need to wait for the
IPI, we can avoid it completely.

Also
1: No need atomically to read/write ->mode in vcpu's thread

2: reorganize struct kvm_vcpu to make ->mode and ->requests
   in the same cache line explicitly

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 70d224d4264c..8213efe1998c 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -662,6 +662,7 @@ again:
                 goto vcpu_run_fail;
 
         srcu_read_unlock(&vcpu->kvm->srcu, idx);
+        vcpu->mode = IN_GUEST_MODE;
         kvm_guest_enter();
 
         /*
@@ -683,6 +684,7 @@ again:
          */
         barrier();
         kvm_guest_exit();
+        vcpu->mode = OUTSIDE_GUEST_MODE;
         preempt_enable();
 
         idx = srcu_read_lock(&vcpu->kvm->srcu);