Re: [Xen-devel] [Qemu-devel] [PATCH] x86: Skip check apic_id_limit for Xen

[Eduardo Habkost <ehabkost@xxxxxxxxxx>]

On Mon, Aug 21, 2017 at 10:22:15AM +0800, Lan Tianyu wrote:
> On 2017年08月19日 00:38, Eduardo Habkost wrote:
> > On Thu, Aug 17, 2017 at 09:37:10AM +0800, Lan Tianyu wrote:
> >> On 2017年08月16日 19:21, Paolo Bonzini wrote:
> >>> On 16/08/2017 02:22, Lan Tianyu wrote:
> >>>> Xen vIOMMU device model will be in Xen hypervisor. Skip vIOMMU
> >>>> check for Xen here when vcpu number is more than 255.
> >>>
> >>> I think you still need to do a check for vIOMMU being enabled.
> >>
> >> Yes, this will be done in the Xen tool stack and Qemu doesn't have such
> >> knowledge. Operations of create, destroy Xen vIOMMU will be done in the
> >> Xen tool stack.
> > 
> > Shouldn't we make QEMU have knowledge of the vIOMMU device, then?
> > Won't QEMU need to know about it eventually?
> > 
> 
> Hi Eduardo:
>      Thanks for your review.
>      Xen has some guest modes which doesn't use Qemu and we tried to
> make Xen vIOMMU framework compatible with all guest modes. So far, we
> are adding interrupt remapping function for Xen vIOMMU and find qemu
> doesn't need to know Xen vIOMMU. The check of vcpu number > 255 here
> will be done in Xen side and so skip the check in Qemu to avoid blocking
> Xen creating >255 vcpus.
>      We may make Qemu have knowledge of the vIOMMU device if it's
> necessary when adding new function.

I was expecting it to go through the PC tree, but I will queue it
on x86-next instead.

-- 
Eduardo

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