intel-iommu: set iommu_superpage on VM domains to lowest common denominator

set dmar->iommu_superpage field to the smallest common denominator
of super page sizes supported by all active VT-d engines.  Initialize
this field in intel_iommu_domain_init() API so intel_iommu_map() API
will be able to use iommu_superpage field to determine the appropriate
super page size to use.

Signed-off-by: Allen Kay <allen.m.kay@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/iommu/intel-iommu.c

@@ -580,17 +580,18 @@ static void domain_update_iommu_snooping(struct dmar_domain *domain)
 
 static void domain_update_iommu_superpage(struct dmar_domain *domain)
 {
-	int i, mask = 0xf;
+	struct dmar_drhd_unit *drhd;
+	struct intel_iommu *iommu = NULL;
+	int mask = 0xf;
 
 	if (!intel_iommu_superpage) {
 		domain->iommu_superpage = 0;
 		return;
 	}
 
-	domain->iommu_superpage = 4; /* 1TiB */
-
-	for_each_set_bit(i, &domain->iommu_bmp, g_num_of_iommus) {
-		mask |= cap_super_page_val(g_iommus[i]->cap);
+	/* set iommu_superpage to the smallest common denominator */
+	for_each_active_iommu(iommu, drhd) {
+		mask &= cap_super_page_val(iommu->cap);
 		if (!mask) {
 			break;
 		}
@@ -3748,6 +3749,7 @@ static int intel_iommu_domain_init(struct iommu_domain *domain)
 		vm_domain_exit(dmar_domain);
 		return -ENOMEM;
 	}
+	domain_update_iommu_cap(dmar_domain);
 	domain->priv = dmar_domain;
 
 	return 0;