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SubjectRe: [PATCH] kvm: x86: fix a race condition result to lost INIT
2017-07-31 0:24 GMT+08:00 Peng Hao <peng.hao2@zte.com.cn>:
> 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
> events->smi.latched_init == 0
> clear INIT in pending_events
> I don't think it need set/clear kernel state according to userspace's
> info.
>
> Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
> ---
> arch/x86/kvm/x86.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6c7266f..393a7b7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3157,12 +3157,6 @@ 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);

This is not correct, you will lose the INIT after live migration. I
just send out another patch to fix it. Thanks for the report.

Regards,
Wanpeng Li

> - else
> - clear_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
> - }
> }
>
> kvm_make_request(KVM_REQ_EVENT, vcpu);
> --
> 1.8.3.1
>
>

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