[PATCH hulk-4.19-next] KVM: Check preempted_in_kernel for involuntary preemption
From: Wanpeng Li <wanpengli@tencent.com> mainline inclusion from mainline-v5.8-rc5 commit 046ddeed0461b5d270470c253cbb321103d048b6 category: feature bugzilla: NA DTS: NA CVE: NA -------------------------------- 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> Signed-off-by: Paolo Bonzini <pbonzini@redhat.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 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); -- 2.19.1
Reviewed-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
-----Original Message----- From: yezengruan Sent: Tuesday, August 4, 2020 3:41 PM To: Xiexiuqi <xiexiuqi@huawei.com>; Guohanjun (Hanjun Guo) <guohanjun@huawei.com> Cc: Wanghaibin (D) <wanghaibin.wang@huawei.com>; Fanhenglong <fanhenglong@huawei.com>; yezengruan <yezengruan@huawei.com>; Zhanghailiang <zhang.zhanghailiang@huawei.com>; kernel.openeuler <kernel.openeuler@huawei.com>; Chenzhendong (alex) <alex.chen@huawei.com>; virt@openeuler.org; Xiexiangyou <xiexiangyou@huawei.com>; yuzenghui <yuzenghui@huawei.com> Subject: [PATCH hulk-4.19-next] KVM: Check preempted_in_kernel for involuntary preemption
From: Wanpeng Li <wanpengli@tencent.com>
mainline inclusion from mainline-v5.8-rc5 commit 046ddeed0461b5d270470c253cbb321103d048b6 category: feature bugzilla: NA DTS: NA CVE: NA
--------------------------------
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> Signed-off-by: Paolo Bonzini <pbonzini@redhat.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 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); -- 2.19.1
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