Re: [PATCH] KVM: VMX: Fix race between pending IRQ and NMI

[Avi Kivity <avi@redhat.com>]

Jan Kiszka wrote:
>>>> But I think I see a bigger issue - if we inject an regular interrupt
>>>> while another is pending, then we will encounter this problem.  Looks
>>>> like we have to enable the interrupt window after injecting an interrupt
>>>> if there are still pending interrupts.
>>>>     
>>>>         
>>> Yeah, probably. I'm just wondering now if we can set
>>> exit-on-interrupt-window while the vcpu state is interruptible (ie.
>>> _before_ the injection). There is some entry check like this for NMIs,
>>> but maybe no for interrupts. Need to check.
>>>   
>>>       
>> Turns out it's not necessary, since the guest eoi will cause an exit and
>> allow the code to request an interrupt window.
>>     
>
> But you added explicit handling now nevertheless?
>   

Yes, in case some eoi-less mode is introduced either by hardware or 
paravirt.  I regard the fact that it works as accidental (though applies 
to  x86 virtualization in general).

>> I've added an apic test program so we can track these issues
>> (user/test/x86/apic.c).
>>
>>     
>
> That's good. BTW, your NMI race fix is still lacking support for the
> -no-kvm-irqchip case. Will post an according patch later today.
>   

Actually, I couldn't get the 5.2 guest to boot with -no-kvm-irqchip: it 
hangs and needs some help by running 'info registers'.

-- 
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