iommu/arm-smmu-v3: Make domain_alloc_paging_flags() directly determine the S1/S2

The selection of S1/S2 is a bit indirect today, make
domain_alloc_paging_flags() directly decode the flags and select the
correct S1/S2 type.

Directly reject flag combinations the HW doesn't support when processing
the flags.

Fix missing rejection of some flag combinations that are not supported
today (ie NEST_PARENT | DIRTY_TRACKING) by using a switch statement to
list out exactly the combinations that are currently supported.

Move the determination of the stage out of arm_smmu_domain_finalise() and
into both callers. As today the default stage is S1 if supported in HW.

This makes arm_smmu_domain_alloc_paging_flags() self contained and no
longer calling arm_smmu_domain_alloc_paging().

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v1-0bb8d5313a27+27b-smmuv3_paging_flags_jgg@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: jgunthorpe

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -2481,6 +2481,11 @@ static struct iommu_domain *arm_smmu_domain_alloc_paging(struct device *dev)
 	if (IS_ERR(smmu_domain))
 		return ERR_CAST(smmu_domain);
 
+	if (master->smmu->features & ARM_SMMU_FEAT_TRANS_S1)
+		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
+	else
+		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
+
 	ret = arm_smmu_domain_finalise(smmu_domain, master->smmu, 0);
 	if (ret) {
 		kfree(smmu_domain);
@@ -2554,12 +2559,6 @@ static int arm_smmu_domain_finalise(struct arm_smmu_domain *smmu_domain,
 				 struct arm_smmu_domain *smmu_domain);
 	bool enable_dirty = flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
 
-	/* Restrict the stage to what we can actually support */
-	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1))
-		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
-	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S2))
-		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
-
 	pgtbl_cfg = (struct io_pgtable_cfg) {
 		.pgsize_bitmap	= smmu->pgsize_bitmap,
 		.coherent_walk	= smmu->features & ARM_SMMU_FEAT_COHERENCY,
@@ -3231,6 +3230,7 @@ arm_smmu_domain_alloc_paging_flags(struct device *dev, u32 flags,
 				   const struct iommu_user_data *user_data)
 {
 	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+	struct arm_smmu_device *smmu = master->smmu;
 	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
 				 IOMMU_HWPT_ALLOC_PASID |
 				 IOMMU_HWPT_ALLOC_NEST_PARENT;
@@ -3242,25 +3242,43 @@ arm_smmu_domain_alloc_paging_flags(struct device *dev, u32 flags,
 	if (user_data)
 		return ERR_PTR(-EOPNOTSUPP);
 
-	if (flags & IOMMU_HWPT_ALLOC_PASID)
-		return arm_smmu_domain_alloc_paging(dev);
-
 	smmu_domain = arm_smmu_domain_alloc();
 	if (IS_ERR(smmu_domain))
 		return ERR_CAST(smmu_domain);
 
-	if (flags & IOMMU_HWPT_ALLOC_NEST_PARENT) {
-		if (!(master->smmu->features & ARM_SMMU_FEAT_NESTING)) {
+	switch (flags) {
+	case 0:
+		/* Prefer S1 if available */
+		if (smmu->features & ARM_SMMU_FEAT_TRANS_S1)
+			smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
+		else
+			smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
+		break;
+	case IOMMU_HWPT_ALLOC_NEST_PARENT:
+		if (!(smmu->features & ARM_SMMU_FEAT_NESTING)) {
 			ret = -EOPNOTSUPP;
 			goto err_free;
 		}
 		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
 		smmu_domain->nest_parent = true;
+		break;
+	case IOMMU_HWPT_ALLOC_DIRTY_TRACKING:
+	case IOMMU_HWPT_ALLOC_DIRTY_TRACKING | IOMMU_HWPT_ALLOC_PASID:
+	case IOMMU_HWPT_ALLOC_PASID:
+		if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1)) {
+			ret = -EOPNOTSUPP;
+			goto err_free;
+		}
+		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+		goto err_free;
 	}
 
 	smmu_domain->domain.type = IOMMU_DOMAIN_UNMANAGED;
 	smmu_domain->domain.ops = arm_smmu_ops.default_domain_ops;
-	ret = arm_smmu_domain_finalise(smmu_domain, master->smmu, flags);
+	ret = arm_smmu_domain_finalise(smmu_domain, smmu, flags);
 	if (ret)
 		goto err_free;
 	return &smmu_domain->domain;