Re: [PATCH] hw/intc/arm_gic_kvm: Don't assume kernel can provide a GICv2

[Auger Eric <eric.auger@redhat.com>]

Hi Peter,

On 2/26/20 10:17 AM, Andrew Jones wrote:
> On Wed, Feb 26, 2020 at 08:56:03AM +0000, Peter Maydell wrote:
>> On Wed, 26 Feb 2020 at 08:52, Andrew Jones <drjones@redhat.com> wrote:
>>> Although, many QEMU command line users still won't know what to do
>>> without an explicit "Try -machine gic-version=host" hint, so that
>>> might be nice to add too.
>>
>> In the GIC code we don't know if the machine even has a
>> gic-version property, so we're not in the right place to try to
>> produce that message.
>>
> 
> Ah yes, we use qdev_init_nofail() in virt::create_gic(), so there's
> no chance to append another hint at the machine level.
> 
> And what about when machine.gic-version is not provided and KVM is
> in use? Shouldn't we try version '2', as we do now, but then also
> '3', if '2' fails, before erroring out?

In case of KVM accelerated mode we could effectively probe v2 first and
if not supported choose v3, as mentioned by Drew.

Couldn't kvm_arm_vgic_probe() return a bitmap by calling
kvm_create_device on both versions in dryrun mode?

Thanks

Eric

> 
> Thanks,
> drew
> 
>