From 9ee83635d872812f3920209c606c6ea9e412ffcc Mon Sep 17 00:00:00 2001 From: Li RongQing Date: Wed, 9 Feb 2022 12:16:41 +0800 Subject: [PATCH] KVM: x86: Yield to IPI target vCPU only if it is busy When sending a call-function IPI-many to vCPUs, yield to the IPI target vCPU which is marked as preempted. but when emulating HLT, an idling vCPU will be voluntarily scheduled out and mark as preempted from the guest kernel perspective. yielding to idle vCPU is pointless and increase unnecessary vmexit, maybe miss the true preempted vCPU so yield to IPI target vCPU only if vCPU is busy and preempted Signed-off-by: Li RongQing Message-Id: <1644380201-29423-1-git-send-email-lirongqing@baidu.com> Signed-off-by: Paolo Bonzini --- arch/x86/kernel/kvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 491e1d9ca750..d77481ecb0d5 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -624,7 +624,7 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask) /* Make sure other vCPUs get a chance to run if they need to. */ for_each_cpu(cpu, mask) { - if (vcpu_is_preempted(cpu)) { + if (!idle_cpu(cpu) && vcpu_is_preempted(cpu)) { kvm_hypercall1(KVM_HC_SCHED_YIELD, per_cpu(x86_cpu_to_apicid, cpu)); break; }