From 046ddeed0461b5d270470c253cbb321103d048b6 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Thu, 1 Aug 2019 11:30:14 +0800 Subject: [PATCH] KVM: Check preempted_in_kernel for involuntary preemption MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit preempted_in_kernel is updated in preempt_notifier when involuntary preemption ocurrs, it can be stale when the voluntarily preempted vCPUs are taken into account by kvm_vcpu_on_spin() loop. This patch lets it just check preempted_in_kernel for involuntary preemption. Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 887f3b0c2b60..ed061d8a457c 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2508,7 +2508,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) continue; if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu)) continue; - if (yield_to_kernel_mode && !kvm_arch_vcpu_in_kernel(vcpu)) + if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode && + !kvm_arch_vcpu_in_kernel(vcpu)) continue; if (!kvm_vcpu_eligible_for_directed_yield(vcpu)) continue; @@ -4205,7 +4206,7 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu) { struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn); - vcpu->preempted = false; + WRITE_ONCE(vcpu->preempted, false); WRITE_ONCE(vcpu->ready, false); kvm_arch_sched_in(vcpu, cpu); @@ -4219,7 +4220,7 @@ static void kvm_sched_out(struct preempt_notifier *pn, struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn); if (current->state == TASK_RUNNING) { - vcpu->preempted = true; + WRITE_ONCE(vcpu->preempted, true); WRITE_ONCE(vcpu->ready, true); } kvm_arch_vcpu_put(vcpu); -- 2.34.1