Commit 9ee83635 authored by Li RongQing's avatar Li RongQing Committed by Paolo Bonzini
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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: default avatarLi RongQing <lirongqing@baidu.com>
Message-Id: <1644380201-29423-1-git-send-email-lirongqing@baidu.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 92e68cc5

arch/x86/kernel/kvm.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

		}