iommu/amd: Fully decode all combinations of alloc_paging_flags

JIRA: https://issues.redhat.com/browse/RHEL-78704
Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

commit 082f1bc
Author: Jason Gunthorpe <jgg@ziepe.ca>
Date:   Fri Jan 10 12:35:05 2025 -0400

    iommu/amd: Fully decode all combinations of alloc_paging_flags

    Currently AMD does not support
     IOMMU_HWPT_ALLOC_PASID | IOMMU_HWPT_ALLOC_DIRTY_TRACKING

    It should be rejected. Instead it creates a V1 domain without dirty
    tracking support.

    Use a switch to fully decode the flags.

    Fixes: ce2cd17 ("iommu/amd: Enhance amd_iommu_domain_alloc_user()")
    Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
    Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
    Link: https://lore.kernel.org/r/7-v2-9776c53c2966+1c7-amd_paging_flags_jgg@nvidia.com
    Signed-off-by: Joerg Roedel <jroedel@suse.de>

(cherry picked from commit 082f1bc)
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>

Author: snits

drivers/iommu/amd/iommu.c

@@ -2554,24 +2554,24 @@ amd_iommu_domain_alloc_paging_flags(struct device *dev, u32 flags,
 	if ((flags & ~supported_flags) || user_data)
 		return ERR_PTR(-EOPNOTSUPP);
 
-	/* Allocate domain with v2 page table if IOMMU supports PASID. */
-	if (flags & IOMMU_HWPT_ALLOC_PASID) {
+	switch (flags & supported_flags) {
+	case IOMMU_HWPT_ALLOC_DIRTY_TRACKING:
+		/* Allocate domain with v1 page table for dirty tracking */
+		if (!amd_iommu_hd_support(iommu))
+			break;
+		return do_iommu_domain_alloc(dev, flags, PD_MODE_V1);
+	case IOMMU_HWPT_ALLOC_PASID:
+		/* Allocate domain with v2 page table if IOMMU supports PASID. */
 		if (!amd_iommu_pasid_supported())
-			return ERR_PTR(-EOPNOTSUPP);
-
+			break;
 		return do_iommu_domain_alloc(dev, flags, PD_MODE_V2);
+	case 0:
+		/* If nothing specific is required use the kernel commandline default */
+		return do_iommu_domain_alloc(dev, 0, amd_iommu_pgtable);
+	default:
+		break;
 	}
-
-	/* Allocate domain with v1 page table for dirty tracking */
-	if (flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING) {
-		if (amd_iommu_hd_support(iommu))
-			return do_iommu_domain_alloc(dev, flags, PD_MODE_V1);
-
-		return ERR_PTR(-EOPNOTSUPP);
-	}
-
-	/* If nothing specific is required use the kernel commandline default */
-	return do_iommu_domain_alloc(dev, 0, amd_iommu_pgtable);
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 void amd_iommu_domain_free(struct iommu_domain *dom)