[PATCH v2 3/3] KVM: X86: Do not yield to self

[Wanpeng Li]

From: Wanpeng Li <wanpengli@xxxxxxxxxxx>

If the target is self we do not need to yield, we can avoid malicious
guest to play this.

Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
v1 -> v2:
 * update comments

 arch/x86/kvm/x86.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f08e9b4..ce9a1d2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8231,6 +8231,10 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
 	if (!target || !READ_ONCE(target->ready))
 		goto no_yield;
 
+	/* Ignore requests to yield to self */
+	if (vcpu == target)
+		goto no_yield;
+
 	if (kvm_vcpu_yield_to(target) <= 0)
 		goto no_yield;
 
-- 
2.7.4