iommu/vt-d: Match CPU and IOMMU paging mode

When setting up first level page tables for sharing with CPU, we need
to ensure IOMMU can support no less than the levels supported by the
CPU.

It is not adequate, as in the current code, to set up 5-level paging
in PASID entry First Level Paging Mode(FLPM) solely based on CPU.

Currently, intel_pasid_setup_first_level() is only used by native SVM
code which already checks paging mode matches. However, future use of
this helper function may not be limited to native SVM.
https://lkml.org/lkml/2019/11/18/1037

Fixes: 437f35e1 ("iommu/vt-d: Add first level page table interface")
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-pasid.c

@@ -499,8 +499,16 @@ int intel_pasid_setup_first_level(struct intel_iommu *iommu,
 	}
 
 #ifdef CONFIG_X86
-	if (cpu_feature_enabled(X86_FEATURE_LA57))
-		pasid_set_flpm(pte, 1);
+	/* Both CPU and IOMMU paging mode need to match */
+	if (cpu_feature_enabled(X86_FEATURE_LA57)) {
+		if (cap_5lp_support(iommu->cap)) {
+			pasid_set_flpm(pte, 1);
+		} else {
+			pr_err("VT-d has no 5-level paging support for CPU\n");
+			pasid_clear_entry(pte);
+			return -EINVAL;
+		}
+	}
 #endif /* CONFIG_X86 */
 
 	pasid_set_domain_id(pte, did);