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From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: [PATCH v4 3/6] KVM: Check preempted_in_kernel for involuntary preemption
Date: Mon,  5 Aug 2019 10:03:21 +0800	[thread overview]
Message-ID: <1564970604-10044-3-git-send-email-wanpengli@tencent.com> (raw)
In-Reply-To: <1564970604-10044-1-git-send-email-wanpengli@tencent.com>

From: Wanpeng Li <wanpengli@tencent.com>

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 <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 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 e121423..2ae9e84 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2522,7 +2522,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
 				continue;
 			if (swait_active(&vcpu->wq) && !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;
@@ -4219,7 +4220,7 @@ 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);
@@ -4233,7 +4234,7 @@ 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);
-- 
2.7.4


  parent reply	other threads:[~2019-08-05  2:03 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-05  2:03 [PATCH v4 1/6] KVM: Fix leak vCPU's VMCS value into other pCPU Wanpeng Li
2019-08-05  2:03 ` [PATCH v4 2/6] KVM: LAPIC: Don't need to wakeup vCPU twice afer timer fire Wanpeng Li
2019-08-05  2:03 ` Wanpeng Li [this message]
2019-08-05  2:03 ` [PATCH v4 4/6] KVM: X86: Use IPI shorthands in kvm guest when support Wanpeng Li
2019-08-05  2:03 ` [PATCH v4 5/6] KVM: LAPIC: Add pv ipi tracepoint Wanpeng Li
2019-08-05  2:03 ` [PATCH v4 6/6] KVM: X86: Add pv tlb shootdown tracepoint Wanpeng Li
2019-08-05 23:17 ` [PATCH v4 1/6] KVM: Fix leak vCPU's VMCS value into other pCPU Paolo Bonzini
2019-08-06  0:35   ` Wanpeng Li
2019-08-06  6:20     ` Paolo Bonzini
2019-08-22  0:46       ` Wanpeng Li
2019-08-22  8:35         ` Paolo Bonzini
2019-08-22  8:45           ` Wanpeng Li

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