iommu/arm-smmu-v3: Implement IOMMU_HWPT_ALLOC_NEST_PARENT

For SMMUv3 the parent must be a S2 domain, which can be composed
into a IOMMU_DOMAIN_NESTED.

In future the S2 parent will also need a VMID linked to the VIOMMU and
even to KVM.

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/6-v4-9e99b76f3518+3a8-smmuv3_nesting_jgg@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: jgunthorpe

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

@@ -3114,7 +3114,8 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
 			   const struct iommu_user_data *user_data)
 {
 	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
-	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
+	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
+				 IOMMU_HWPT_ALLOC_NEST_PARENT;
 	struct arm_smmu_domain *smmu_domain;
 	int ret;
 
@@ -3127,6 +3128,14 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
 	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)) {
+			ret = -EOPNOTSUPP;
+			goto err_free;
+		}
+		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
+	}
+
 	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);