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 <[email protected]> Signed-off-by: Marcelo Tosatti <[email protected]>
jadonk · Jul 6, 2012 · 5cfc2aa · 5cfc2aa
1 parent 21b26c0
commit 5cfc2aa
Showing 1 changed file with 1 addition and 1 deletion.
diff --git 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)