From: Rik van Riel <riel@redhat.com>
Date: Tue, 19 Jun 2012 20:51:04 +0000 (-0400)
Subject: KVM: handle last_boosted_vcpu = 0 case
X-Git-Tag: upstream/snapshot3+hdmi~6996^2~45
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5cfc2aabcb282f4554e7086c9893b386ad6ba9d4;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

KVM: handle last_boosted_vcpu = 0 case

If last_boosted_vcpu == 0, then we fall through all test cases and
may end up with all VCPUs pouncing on vcpu 0.  With a large enough
guest, this can result in enormous runqueue lock contention, which
can prevent vcpu0 from running, leading to a livelock.

Changing < to <= makes sure we properly handle that case.

Signed-off-by: Rik van Riel <riel@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 636bd08..b3ce91c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1598,7 +1598,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
 	 */
 	for (pass = 0; pass < 2 && !yielded; pass++) {
 		kvm_for_each_vcpu(i, vcpu, kvm) {
-			if (!pass && i < last_boosted_vcpu) {
+			if (!pass && i <= last_boosted_vcpu) {
 				i = last_boosted_vcpu;
 				continue;
 			} else if (pass && i > last_boosted_vcpu)