Re: [PATCH v3 0/2] KVM: ARM: Enable vtimers with user space gic

Paolo Bonzini
2016-09-16T12:54:01Z

On 16/09/2016 14:44, Alexander Graf wrote:
>
>> On 16 Sep 2016, at 14:40, Paolo Bonzini <pbonzini@redhat.com>
>> wrote:
>>
>>
>>
>> On 16/09/2016 14:29, Christoffer Dall wrote:
>>>> It may be useful for migrating a gicv2 VM to a gicv3 host
>>>> without gicv2 emulation as well.
>>>
>>> I don't see why you'd do this; the VGIC hardware can perfectly
>>> well be used for nesting as well, and this works rather well.
>>
>> Can GICv3 emulate GICv2 in a guest?
>
> It depends on the gicv3 configuration. As an SOC vendor you can
> either enable gicv2 compatibility or disable it. ThunderX for example
> is gicv3 only.

And QEMU complains on startup and exits, I hope.

I am not too optimistic about having migration from kernel GIC to
userspace GIC, honestly. But GICv2 emulation on GICv3-only hosts is a
very reasonable thing to want, if only for testing/debugging purposes.

Paolo