Re: [PATCH RFC 10/39] KVM: x86/xen: support upcall vector

[Joao Martins]

On 12/9/20 3:41 PM, David Woodhouse wrote:
> On 9 December 2020 13:26:55 GMT, Joao Martins <joao.m.martins@xxxxxxxxxx> wrote:
>> On 12/9/20 11:39 AM, David Woodhouse wrote:
>>> As far as I can tell, Xen's hvm_vcpu_has_pending_irq() will still
>>> return the domain-wide vector in preference to the one in the LAPIC,
>> if
>>> it actually gets invoked. 
>>
>> Only if the callback installed is HVMIRQ_callback_vector IIUC.
>>
>> Otherwise the vector would be pending like any other LAPIC vector.
> 
> Ah, right.
> 
> For some reason I had it in my head that you could only set the per-vCPU lapic vector if the domain was set to HVMIRQ_callback_vector. If the domain is set to HVMIRQ_callback_none, that clearly makes more sense.
> 
> Still, my patch should do the same as Xen does in the case where a guest does set both, I think.
> 
> Faithful compatibility with odd Xen behaviour FTW :)
> 
Ah, yes. In that case, HVMIRQ_callback_vector does take precedence.

But it would be very weird for a guest to setup two callback vectors :)