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Re: [Qemu-devel] [PATCH v3] KVM: x86: Fix nmi injection failure when vcp
From: |
Radim Krčmář |
Subject: |
Re: [Qemu-devel] [PATCH v3] KVM: x86: Fix nmi injection failure when vcpu got blocked |
Date: |
Tue, 30 May 2017 15:36:05 +0200 |
2017-05-26 13:16+0800, Zhuangyanying:
> From: ZhuangYanying <address@hidden>
>
> When spin_lock_irqsave() deadlock occurs inside the guest, vcpu threads,
> other than the lock-holding one, would enter into S state because of
> pvspinlock. Then inject NMI via libvirt API "inject-nmi", the NMI could
> not be injected into vm.
>
> The reason is:
> 1 It sets nmi_queued to 1 when calling ioctl KVM_NMI in qemu, and sets
> cpu->kvm_vcpu_dirty to true in do_inject_external_nmi() meanwhile.
> 2 It sets nmi_queued to 0 in process_nmi(), before entering guest, because
> cpu->kvm_vcpu_dirty is true.
>
> It's not enough just to check nmi_queued to decide whether to stay in
> vcpu_block() or not. NMI should be injected immediately at any situation.
> Add checking nmi_pending, and testing KVM_REQ_NMI replaces nmi_queued
> in vm_vcpu_has_events().
>
> Do the same change for SMIs.
>
> Signed-off-by: Zhuang Yanying <address@hidden>
> ---
> v1->v2
> - simplify message. The complete description is here:
> http://www.spinics.net/lists/kvm/msg150380.html
> - Testing KVM_REQ_NMI replaces nmi_pending.
> - Add Testing kvm_x86_ops->nmi_allowed(vcpu).
> v2->v3
> - Testing KVM_REQ_NMI replaces nmi_queued, not nmi_pending.
> - Do the same change for SMIs.
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> @@ -8394,10 +8394,13 @@ static inline bool kvm_vcpu_has_events(struct
> kvm_vcpu *vcpu)
> if (vcpu->arch.pv.pv_unhalted)
> return true;
>
> - if (atomic_read(&vcpu->arch.nmi_queued))
> + if (kvm_test_request(KVM_REQ_NMI, vcpu) ||
> + (vcpu->arch.nmi_pending &&
I think the logic should be
if ((kvm_test_request(KVM_REQ_NMI, vcpu) || vcpu->arch.nmi_pending) &&
kvm_x86_ops->nmi_allowed(vcpu))
because there is no reason to resume the VCPU if we cannot inject.
> + kvm_x86_ops->nmi_allowed(vcpu)))
> return true;
>
> - if (kvm_test_request(KVM_REQ_SMI, vcpu))
> + if (kvm_test_request(KVM_REQ_SMI, vcpu) ||
> + (vcpu->arch.smi_pending && !is_smm(vcpu)))
Ditto.
> return true;
>
> if (kvm_arch_interrupt_allowed(vcpu) &&
We'll then be consistent with other interrupts,
Thanks.