Re: [PATCH v3 03/12] iommu: Add new flag to explictly request PASID capable domain

[Vasant Hegde <vasant.hegde@amd.com>]

Hi Yi,


On 10/21/2024 1:27 PM, Yi Liu wrote:
> On 2024/10/17 22:01, Vasant Hegde wrote:
>> From: Jason Gunthorpe <jgg@ziepe.ca>
>>
>> Introduce new flag (IOMMU_HWPT_ALLOC_PASID) to domain_alloc_users() ops.
>> If both IOMMU and device supports PASID it will allocate domain.
>> Otherwise return error.
> 
> I think my iommufd pasid series depends on the flag added here. As Jason
> suggested[1], I would add a check in iommufd to ensure all the domains that
> used in the pasid path are allocated with the IOMMU_HWPT_ALLOC_PASID flag.
> 
> [1]
> https://lore.kernel.org/linux-iommu/5a6c2676-256a-4fa5-b9a0-e433d4e933c9@intel.com/
> 

Sure. Hopefully we have sorted out all the issues. I will post v4 soon.

>>
>> Also modify __iommu_group_alloc_default_domain() to call
>> iommu_paging_domain_alloc_flags() with appropriate flag when allocating
>> paging domain.
>>
>> Signed-off-by: Jason Gunthorpe <jgg@ziepe.ca>
>> [Added __iommu_paging_domain_alloc_flags() and description - Vasant]
>> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
>> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
>> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
>> ---
>>   drivers/iommu/iommu.c        | 45 +++++++++++++++++++++++++++---------


.../...

>> +}
>>   EXPORT_SYMBOL_GPL(iommu_paging_domain_alloc_flags);
>>     void iommu_domain_free(struct iommu_domain *domain)
>> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
>> index 72010f71c5e4..d1b07f4d9d32 100644
>> --- a/include/uapi/linux/iommufd.h
>> +++ b/include/uapi/linux/iommufd.h
>> @@ -359,11 +359,17 @@ struct iommu_vfio_ioas {
>>    *                                   enforced on device attachment
>>    * @IOMMU_HWPT_FAULT_ID_VALID: The fault_id field of hwpt allocation data is
>>    *                             valid.
>> + * @IOMMU_HWPT_ALLOC_PASID: Requests a domain that can be used with PASID. The
>> + *                          domain can be attached to any PASID on the device.
>> + *                          Any domain attached to the non-PASID part of the
>> + *                          device must also be flaged, otherwise attaching a
>> + *                          PASID will blocked.
> 
> Just a double check.
> 
> Can I interpret this as "all the domains used by a pasid-capable device
> (both the RID and the PASIDs) should be allocated with this flag set"?

If IOMMU supports PASID, then yes. Otherwise it will fallback to non-PASID
domain in DMA-API mode.

-Vasant