iommu/vt-d: Add IOMMU_HWPT_ALLOC_PASID support

Intel iommu driver just treats it as a nop since Intel VT-d does not have
special requirement on domains attached to either the PASID or RID of a
PASID-capable device.

Link: https://patch.msgid.link/r/20250321171940.7213-14-yi.l.liu@intel.com
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: yiliu1765

drivers/iommu/intel/iommu.c

@@ -3338,7 +3338,8 @@ intel_iommu_domain_alloc_paging_flags(struct device *dev, u32 flags,
 	bool first_stage;
 
 	if (flags &
-	    (~(IOMMU_HWPT_ALLOC_NEST_PARENT | IOMMU_HWPT_ALLOC_DIRTY_TRACKING)))
+	    (~(IOMMU_HWPT_ALLOC_NEST_PARENT | IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
+	       IOMMU_HWPT_ALLOC_PASID)))
 		return ERR_PTR(-EOPNOTSUPP);
 	if (nested_parent && !nested_supported(iommu))
 		return ERR_PTR(-EOPNOTSUPP);

drivers/iommu/intel/nested.c

@@ -198,7 +198,7 @@ intel_iommu_domain_alloc_nested(struct device *dev, struct iommu_domain *parent,
 	struct dmar_domain *domain;
 	int ret;
 
-	if (!nested_supported(iommu) || flags)
+	if (!nested_supported(iommu) || flags & ~IOMMU_HWPT_ALLOC_PASID)
 		return ERR_PTR(-EOPNOTSUPP);
 
 	/* Must be nested domain */