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SubjectRe: [PATCH] KVM: X86: Fix loss of pending INIT due to race
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On 30/07/2017 11:42, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@hotmail.com>
>
> When SMP VM start, AP may lost INIT because of receiving INIT between
> kvm_vcpu_ioctl_x86_get/set_vcpu_events.
>
> vcpu 0 vcpu 1
> kvm_vcpu_ioctl_x86_get_vcpu_events
> events->smi.latched_init = 0
> send INIT to vcpu1
> set vcpu1's pending_events
> kvm_vcpu_ioctl_x86_set_vcpu_events
> if (events->smi.latched_init == 0)
> clear INIT in pending_events
>
> This patch fixes it by not touching INIT pending if INIT is not latched
> which in SMM and just restoring the latched INIT after SET_VCPU_EVENTS.
>
> Thanks Peng Hao for the report and original commit message.
>
> Reported-by: Peng Hao <peng.hao2@zte.com.cn>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
> arch/x86/kvm/x86.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 1a4c84d..eaca86d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3164,12 +3164,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
> vcpu->arch.hflags |= HF_SMM_INSIDE_NMI_MASK;
> else
> vcpu->arch.hflags &= ~HF_SMM_INSIDE_NMI_MASK;
> - if (lapic_in_kernel(vcpu)) {
> - if (events->smi.latched_init)
> - set_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
> - else
> - clear_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
> - }
> + if (events->smi.latched_init && lapic_in_kernel(vcpu))
> + set_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);

All this block:

if (events->smi.smm_inside_nmi)
vcpu->arch.hflags |= HF_SMM_INSIDE_NMI_MASK;
else
vcpu->arch.hflags &= ~HF_SMM_INSIDE_NMI_MASK;
if (lapic_in_kernel(vcpu)) {
if (events->smi.latched_init)
set_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
else
clear_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
}

only applies if you're in SMM, so perhaps you can move it under

if (events->smi.smm)

?

Paolo

> }
>
> kvm_make_request(KVM_REQ_EVENT, vcpu);
>

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