Re: [Xen-devel] [PATCH RFC] pass-through: sync pir to irr after msix vector been updated

[Joe Jin <joe.jin@xxxxxxxxxx>]

On 9/20/19 1:28 AM, Jan Beulich wrote:
> On 19.09.2019 23:38, Joe Jin wrote:
>> On 9/19/19 3:24 AM, Jan Beulich wrote:
>>> What's
>>> still missing is the further updating of pirq_dpci->gmsi.dest_vcpu_id
>>> (as explained before, still visible in context above).
>>>
>>
>>  422
>>  423         dest_vcpu_id = hvm_girq_dest_2_vcpu_id(d, dest, dest_mode);
>>  424         pirq_dpci->gmsi.dest_vcpu_id = dest_vcpu_id;
>>
>> dest_vcpu_id updated later by above code, do I missed something?
> 
> This piece of code
> 
>         if ( iommu_intpost )
>         {
>             if ( delivery_mode == dest_LowestPrio )
>                 vcpu = vector_hashing_dest(d, dest, dest_mode,
>                                            pirq_dpci->gmsi.gvec);
>             if ( vcpu )
>                 pirq_dpci->gmsi.posted = true;
>         }
> 
> updates the vCPU to be delivered to. Right now, when the "posted"
> flag is set, the dest_vcpu_id field is unused (as far as I was
> able to tell), and hence didn't need setting. The way you intend
> to change things, you want to use the field also in the "posted"
> case, and hence you also should update it in the code path above.
> 
> But please double check all of this.

Thanks for your explanation.

I did not found any other possible conditions which may lead invalid
setting, seems ( dest_vcpu_id >=0 && pirq_dpci->gmsi.posted ) is enough?

Thanks,
Joe



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