Re: [PATCH 07/11] hw/arm/smmuv3-accel: Implement "auto" value for "ssidsize"

[Nathan Chen <nathanc@nvidia.com>]

On 4/10/2026 12:56 AM, Eric Auger wrote:
> 
> On 4/1/26 3:02 AM, Nathan Chen wrote:
>> From: Nathan Chen<nathanc@nvidia.com>
>>
>> Allow accelerated SMMUv3 SSID size property to be derived from host
>> IOMMU capabilities. Derive host values using IOMMU_GET_HW_INFO,
>> retrieving SSID size from IDR1. When the auto SSID size is resolved
>> to a non-zero value, PASID capability is advertised to the vIOMMU
>> and accelerated use cases such as Shared Virtual Addressing (SVA)
>> are supported.
>>
>> Signed-off-by: Nathan Chen<nathanc@nvidia.com>
>> ---
>>   hw/arm/smmuv3-accel.c | 14 ++++++++++++--
>>   hw/arm/smmuv3.c       | 11 +++++------
>>   2 files changed, 17 insertions(+), 8 deletions(-)
>>
>> diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
>> index 9e7ec6a930..03393fd7ba 100644
>> --- a/hw/arm/smmuv3-accel.c
>> +++ b/hw/arm/smmuv3-accel.c
>> @@ -56,6 +56,13 @@ static void smmuv3_accel_auto_finalise(SMMUv3State *s,
>>                                  FIELD_EX32(info->idr[3], IDR3, RIL));
>>       }
>>   
>> +    /* Update SSIDSIZE if auto from info */
>> +    if (s->ssidsize == SSID_SIZE_MODE_AUTO) {
>> +        /* Store for get_viommu_flags() to determine PASID support */
>> +        s->idr[1] = FIELD_DP32(s->idr[1], IDR1, SSIDSIZE,
>> +                               FIELD_EX32(info->idr[1], IDR1, SSIDSIZE));
>> +    }
>> +
>>       accel->auto_finalised = true;
>>   }
>>   
>> @@ -828,7 +835,9 @@ static uint64_t smmuv3_accel_get_viommu_flags(void *opaque)
>>       SMMUState *bs = opaque;
>>       SMMUv3State *s = ARM_SMMUV3(bs);
>>   
>> -    if (s->ssidsize > SSID_SIZE_MODE_0) {
>> +    if (s->ssidsize > SSID_SIZE_MODE_0 ||
>> +        (s->ssidsize == SSID_SIZE_MODE_AUTO &&
> maybe worth adding a short static inline helper pasid_is_supported(s)?
Yes, I will include that in the next refresh. It should look cleaner in 
smmuv3_accel_get_viommu_flags() that way.

Thanks,
Nathan