Re: [PATCH v4 12/17] hw/arm: virt: cleanly fail on attempt to use the platform vGIC together with ITS

[Mohamed Mediouni]

> On 5. Aug 2025, at 00:59, Philippe Mathieu-Daudé <phi...@linaro.org> wrote:
> 
> On 4/8/25 16:23, Mohamed Mediouni wrote:
>> Windows Hypervisor Platform's vGIC doesn't support ITS.
>> Deal with this by reporting to the user and not creating the ITS device.
>> Signed-off-by: Mohamed Mediouni <moha...@unpredictable.fr>
>> ---
>>  hw/arm/virt.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index 98a1c74c42..0039f6a12b 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -741,6 +741,16 @@ static void create_its(VirtMachineState *vms)
>>          return;
>>      }
>>  +    if (whpx_enabled() && vms->tcg_its) {
>> +        /*
>> +         * Signal to the user when ITS is neither supported by the host
>> +         * nor emulated by the machine.
>> +         */
>> +        info_report("ITS not supported on WHPX.");
>> +        info_report("To support MSIs, use its=off to enable GICv3 + 
>> GICv2m.");
> 
> So if the users deliberately asks for its=on, we ignore the request and
> keep going. Shouldn't we just exit so the user adapts its command line?
Maybe that’s the best way to go… what makes me a bit hesitant on that one 
though is that the default is its=on.
>> +        return;
>> +    }
>> +
>>      dev = qdev_new(its_class_name());
>>        object_property_set_link(OBJECT(dev), "parent-gicv3", 
>> OBJECT(vms->gic),
> 
>