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SubjectRe: [PATCH] KVM: X86: Fix loss of pending INIT due to race
2017-08-02 0:27 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> 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)
>
> ?

Good point, I will do it in v2.

Regards,
Wanpeng Li

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

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