Re: [PATCH v2 7/7] qemu-options.hx: Support "auto" for accel SMMUv3 properties

[Nathan Chen <nathanc@nvidia.com>]

Hi Eric,

On 5/8/2026 5:08 AM, Eric Auger wrote:
> Hi Nathan,
> On 4/22/26 10:43 PM, Nathan Chen wrote:
>> Update documentation now that "auto" is supported for accelerated SMMUv3
>> properties.
>>
>> Signed-off-by: Nathan Chen<nathanc@nvidia.com>
>> ---
>>   qemu-options.hx | 33 +++++++++++++++++++++++----------
>>   1 file changed, 23 insertions(+), 10 deletions(-)
>>
>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index 21972f8326..2c6ba16a26 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -1291,30 +1291,43 @@ SRST
>>           Enabling accel configures the host SMMUv3 in nested mode to support
>>           vfio-pci passthrough.
>>   
>> -     The following options are available when accel=on.
>> -     Note: 'auto' mode is not currently supported.
>> -
>> -    ``ril=on|off`` (default: on)
>> +     The following options will be set to auto by default if not manually
>> +     set. When accel=on and these properties are set to auto, the value is
>> +     derived from the host SMMUv3 capabilities via IOMMU_GET_HW_INFO. With
>> +     accel=on, this requires at least one cold-plugged vfio-pci device; if
>> +     none is present at machine init, QEMU will abort.
>> +
>> +     If accel=off and these property values are set to auto, the values will
>> +     not be derived from the host SMMUv3 capabilities. Instead, they will
>> +     resolve to the defaults described below, and a cold-plugged vfio-pci
>> +     device is not required.
> I would simply say:
> 
> If accel=off auto values resolve to the non accel default given below.
> 
Got it, I will simplify the accel=off explanation accordingly.

> 
>> +
>> +    ``ril=on|off`` (default: auto)
> ril=on|off|auto (default: auto)
>            -------
> 
> I would rewrite it into:
> 
> Support for Range Invalidation, which allows the SMMUv3 driver to
> invalidate TLB entries for a range of IOVAs at once instead of issuing
> separate commands to invalidate each page.
> - with accel=on auto means the value is automatically derived from the host SMMU
>    if explicitly set to 'on', the host must also support it.
> - with accel=off auto is resolved into 'on'
> 
> If we have this explanation here in object_class_property_set_description()
> just explain the basic semantic and list the valid values and default value.
> No use to rexplain the auto mode semantic.
> 
> 
> 
>>           Support for Range Invalidation, which allows the SMMUv3 driver to
>>           invalidate TLB entries for a range of IOVAs at once instead of issuing
>>           separate commands to invalidate each page. Must match with host SMMUv3
>> -        Range Invalidation support.
>> +        Range Invalidation support. If accel=off and ril is set to auto, this
>> +        property value will resolve to on.
> Same for the others ...
Ok, I will leave the auto explanation out of 
object_class_property_set_description() and keep it here.

Thanks,
Nathan