path: root/virt
diff options
authorLi RongQing <>2021-07-27 19:12:47 +0800
committerPaolo Bonzini <>2021-07-27 16:59:01 -0400
commit74775654332b2682a5580d6f954e5a9ac81e7477 (patch)
tree36e5a720e26b554856d3db47524f2369c8bd2d6a /virt
parent5868b8225ecef4ba3f5b17e65984d60bc5fd6254 (diff)
KVM: use cpu_relax when halt polling
SMT siblings share caches and other hardware, and busy halt polling will degrade its sibling performance if its sibling is working Sean Christopherson suggested as below: "Rather than disallowing halt-polling entirely, on x86 it should be sufficient to simply have the hardware thread yield to its sibling(s) via PAUSE. It probably won't get back all performance, but I would expect it to be close. This compiles on all KVM architectures, and AFAICT the intended usage of cpu_relax() is identical for all architectures." Suggested-by: Sean Christopherson <> Signed-off-by: Li RongQing <> Message-Id: <> Signed-off-by: Paolo Bonzini <>
Diffstat (limited to 'virt')
1 files changed, 1 insertions, 0 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 986959833d70..0d732813fa80 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3110,6 +3110,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
goto out;
+ cpu_relax();
poll_end = cur = ktime_get();
} while (kvm_vcpu_can_poll(cur, stop));