Re: [PATCH v8 12/29] iommufd/viommu: Add driver-defined vDEVICE support

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

On 7/5/2025 6:43 AM, Nicolin Chen wrote:
> NVIDIA VCMDQ driver will have a driver-defined vDEVICE structure and do
> some HW configurations with that.
> 
> To allow IOMMU drivers to define their own vDEVICE structures, move the
> struct iommufd_vdevice to the public header and provide a pair of viommu
> ops, similar to get_viommu_size and viommu_init.
> 
> Doing this, however, creates a new window between the vDEVICE allocation
> and its driver-level initialization, during which an abort could happen
> but it can't invoke a driver destroy function from the struct viommu_ops
> since the driver structure isn't initialized yet. vIOMMU object doesn't
> have this problem, since its destroy op is set via the viommu_ops by the
> driver viommu_init function. Thus, vDEVICE should do something similar:
> add a destroy function pointer inside the struct iommufd_vdevice instead
> of the struct iommufd_viommu_ops.
> 
> Note that there is unlikely a use case for a type dependent vDEVICE, so
> a static vdevice_size is probably enough for the near term instead of a
> get_vdevice_size function op.
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Pranjal Shrivastava <praan@google.com>
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>

-Vasant