RE: [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is set

[Zhang, Yang Z]

Paolo Bonzini wrote on 2014-12-18:
> 
> 
> On 18/12/2014 04:14, Wu, Feng wrote:
>> 
>> 
>> linux-kernel-owner@xxxxxxxxxxxxxxx wrote on mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of Paolo:
>>> x86@xxxxxxxxxx; Gleb Natapov; Paolo Bonzini; dwmw2@xxxxxxxxxxxxx;
>>> joro-zLv9SwRftAIdnm+yROfE0A@xxxxxxxxxxxxxxxx; Alex Williamson;
>>> joro-zLv9SwRftAIdnm+Jiang
>>> Liu
>>> Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx;
>>> linux-kernel-u79uwXL29TY76Z2rM5mHXA@xxxxxxxxxxxxxxxx; KVM list;
>>> Eric Auger
>>> Subject: Re: [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is
>>> set
>>> 
>>> 
>>> 
>>> On 12/12/2014 16:14, Feng Wu wrote:
>>>> Currently, we don't support urgent interrupt, all interrupts are
>>>> recognized as non-urgent interrupt, so we cannot send
>>>> posted-interrupt when 'SN' is set.
>>> 
>>> Can this happen?  If the vcpu is in guest mode, it cannot have been
>>> scheduled out, and that's the only case when SN is set.
>>> 
>>> Paolo
>> 
>> Currently, the only place where SN is set is vCPU is preempted and

If the vCPU is preempted, shouldn't the subsequent be ignored? What happens if a PI is occurs when vCPU is preempted?

>> waiting for the next scheduling in the runqueue. But I am not sure
>> whether we need to set SN for other purpose in future. Adding SN
>> checking here is just to follow the Spec. non-urgent interrupts are
>> suppressed
> when SN is set.
> 
> I would change that to a WARN_ON_ONCE then.


Best regards,
Yang


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