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

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

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.

-- 
Best regards
Tianyu Lan

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