| Message ID | 1644380201-29423-1-git-send-email-lirongqing@baidu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Yield to IPI target vCPU only if it is busy | expand |
On 2/9/22 05:16, Li RongQing wrote: > 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 <lirongqing@baidu.com> > --- > 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 355fe8b..58749f2 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -619,7 +619,7 @@ 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; > } Queued, thanks. Paolo
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 355fe8b..58749f2 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -619,7 +619,7 @@ 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; }
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 <lirongqing@baidu.com> --- arch/x86/kernel/kvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)