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KVM: handle last_boosted_vcpu = 0 case

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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>
This commit is contained in:
Rik van Riel 2012-06-19 16:51:04 -04:00 committed by Marcelo Tosatti
parent 21b26c0853
commit 5cfc2aabcb
1 changed files with 1 additions and 1 deletions
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2
virt/kvm/kvm_main.c
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@ -1598,7 +1598,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
*/ */
for (pass = 0; pass < 2 && !yielded; pass++) { for (pass = 0; pass < 2 && !yielded; pass++) {
kvm_for_each_vcpu(i, vcpu, kvm) { kvm_for_each_vcpu(i, vcpu, kvm) {
if (!pass && i < last_boosted_vcpu) { if (!pass && i <= last_boosted_vcpu) {
i = last_boosted_vcpu; i = last_boosted_vcpu;
continue; continue;
} else if (pass && i > last_boosted_vcpu) } else if (pass && i > last_boosted_vcpu)