iommu/vt-d: Split paging_domain_compatible()

Make First/Second stage specific functions that follow the same pattern in
intel_iommu_domain_alloc_first/second_stage() for computing
EOPNOTSUPP. This makes the code easier to understand as if we couldn't
create a domain with the parameters for this IOMMU instance then we
certainly are not compatible with it.

Check superpage support directly against the per-stage cap bits and the
pgsize_bitmap.

Add a note that the force_snooping is read without locking. The locking
needs to cover the compatible check and the add of the device to the list.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/7-v3-dbbe6f7e7ae3+124ffe-vtd_prep_jgg@nvidia.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20250714045028.958850-10-baolu.lu@linux.intel.com
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 54 insertions, 12 deletions

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index d2451a8ee6e7..3e774e3bb735 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3431,33 +3431,75 @@ static void intel_iommu_domain_free(struct iommu_domain *domain)
 	kfree(dmar_domain);
 }
 
+static int paging_domain_compatible_first_stage(struct dmar_domain *dmar_domain,
+						struct intel_iommu *iommu)
+{
+	if (WARN_ON(dmar_domain->domain.dirty_ops ||
+		    dmar_domain->nested_parent))
+		return -EINVAL;
+
+	/* Only SL is available in legacy mode */
+	if (!sm_supported(iommu) || !ecap_flts(iommu->ecap))
+		return -EINVAL;
+
+	/* Same page size support */
+	if (!cap_fl1gp_support(iommu->cap) &&
+	    (dmar_domain->domain.pgsize_bitmap & SZ_1G))
+		return -EINVAL;
+	return 0;
+}
+
+static int
+paging_domain_compatible_second_stage(struct dmar_domain *dmar_domain,
+				      struct intel_iommu *iommu)
+{
+	unsigned int sslps = cap_super_page_val(iommu->cap);
+
+	if (dmar_domain->domain.dirty_ops && !ssads_supported(iommu))
+		return -EINVAL;
+	if (dmar_domain->nested_parent && !nested_supported(iommu))
+		return -EINVAL;
+
+	/* Legacy mode always supports second stage */
+	if (sm_supported(iommu) && !ecap_slts(iommu->ecap))
+		return -EINVAL;
+
+	/* Same page size support */
+	if (!(sslps & BIT(0)) && (dmar_domain->domain.pgsize_bitmap & SZ_2M))
+		return -EINVAL;
+	if (!(sslps & BIT(1)) && (dmar_domain->domain.pgsize_bitmap & SZ_1G))
+		return -EINVAL;
+	return 0;
+}
+
 int paging_domain_compatible(struct iommu_domain *domain, struct device *dev)
 {
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
 	struct intel_iommu *iommu = info->iommu;
+	int ret = -EINVAL;
 	int addr_width;
 
-	if (WARN_ON_ONCE(!(domain->type & __IOMMU_DOMAIN_PAGING)))
-		return -EPERM;
+	if (intel_domain_is_fs_paging(dmar_domain))
+		ret = paging_domain_compatible_first_stage(dmar_domain, iommu);
+	else if (intel_domain_is_ss_paging(dmar_domain))
+		ret = paging_domain_compatible_second_stage(dmar_domain, iommu);
+	else if (WARN_ON(true))
+		ret = -EINVAL;
+	if (ret)
+		return ret;
 
+	/*
+	 * FIXME this is locked wrong, it needs to be under the
+	 * dmar_domain->lock
+	 */
 	if (dmar_domain->force_snooping && !ecap_sc_support(iommu->ecap))
 		return -EINVAL;
 
-	if (domain->dirty_ops && !ssads_supported(iommu))
-		return -EINVAL;
-
 	if (dmar_domain->iommu_coherency !=
 			iommu_paging_structure_coherency(iommu))
 		return -EINVAL;
 
-	if (dmar_domain->iommu_superpage !=
-			iommu_superpage_capability(iommu, dmar_domain->use_first_level))
-		return -EINVAL;
-
-	if (dmar_domain->use_first_level &&
-	    (!sm_supported(iommu) || !ecap_flts(iommu->ecap)))
-		return -EINVAL;
 
 	/* check if this iommu agaw is sufficient for max mapped address */
 	addr_width = agaw_to_width(iommu->agaw);