diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index b510f67..6dc49ed 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -211,7 +211,7 @@
 
 config INTEL_IOMMU_SVM
 	bool "Support for Shared Virtual Memory with Intel IOMMU"
-	depends on INTEL_IOMMU && X86
+	depends on INTEL_IOMMU && X86_64
 	select PCI_PASID
 	select PCI_PRI
 	select MMU_NOTIFIER
diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index cc46dff..683b812 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -898,7 +898,8 @@
 	if (!ret)
 		ret = dmar_walk_dmar_table((struct acpi_table_dmar *)dmar_tbl,
 					   &validate_drhd_cb);
-	if (!ret && !no_iommu && !iommu_detected && !dmar_disabled) {
+	if (!ret && !no_iommu && !iommu_detected &&
+	    (!dmar_disabled || dmar_platform_optin())) {
 		iommu_detected = 1;
 		/* Make sure ACS will be enabled */
 		pci_request_acs();
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 9129663..d759e72 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -612,6 +612,12 @@
 	return g_iommus[iommu_id];
 }
 
+static inline bool iommu_paging_structure_coherency(struct intel_iommu *iommu)
+{
+	return sm_supported(iommu) ?
+			ecap_smpwc(iommu->ecap) : ecap_coherent(iommu->ecap);
+}
+
 static void domain_update_iommu_coherency(struct dmar_domain *domain)
 {
 	struct dmar_drhd_unit *drhd;
@@ -623,7 +629,7 @@
 
 	for_each_domain_iommu(i, domain) {
 		found = true;
-		if (!ecap_coherent(g_iommus[i]->ecap)) {
+		if (!iommu_paging_structure_coherency(g_iommus[i])) {
 			domain->iommu_coherency = 0;
 			break;
 		}
@@ -634,7 +640,7 @@
 	/* No hardware attached; use lowest common denominator */
 	rcu_read_lock();
 	for_each_active_iommu(iommu, drhd) {
-		if (!ecap_coherent(iommu->ecap)) {
+		if (!iommu_paging_structure_coherency(iommu)) {
 			domain->iommu_coherency = 0;
 			break;
 		}
@@ -921,7 +927,7 @@
 			domain_flush_cache(domain, tmp_page, VTD_PAGE_SIZE);
 			pteval = ((uint64_t)virt_to_dma_pfn(tmp_page) << VTD_PAGE_SHIFT) | DMA_PTE_READ | DMA_PTE_WRITE;
 			if (domain_use_first_level(domain))
-				pteval |= DMA_FL_PTE_XD;
+				pteval |= DMA_FL_PTE_XD | DMA_FL_PTE_US;
 			if (cmpxchg64(&pte->val, 0ULL, pteval))
 				/* Someone else set it while we were thinking; use theirs. */
 				free_pgtable_page(tmp_page);
@@ -1951,7 +1957,6 @@
 context_set_sm_rid2pasid(struct context_entry *context, unsigned long pasid)
 {
 	context->hi |= pasid & ((1 << 20) - 1);
-	context->hi |= (1 << 20);
 }
 
 /*
@@ -2095,7 +2100,8 @@
 
 	context_set_fault_enable(context);
 	context_set_present(context);
-	domain_flush_cache(domain, context, sizeof(*context));
+	if (!ecap_coherent(iommu->ecap))
+		clflush_cache_range(context, sizeof(*context));
 
 	/*
 	 * It's a non-present to present mapping. If hardware doesn't cache
@@ -2243,7 +2249,7 @@
 
 	attr = prot & (DMA_PTE_READ | DMA_PTE_WRITE | DMA_PTE_SNP);
 	if (domain_use_first_level(domain))
-		attr |= DMA_FL_PTE_PRESENT | DMA_FL_PTE_XD;
+		attr |= DMA_FL_PTE_PRESENT | DMA_FL_PTE_XD | DMA_FL_PTE_US;
 
 	if (!sg) {
 		sg_res = nr_pages;
@@ -2695,7 +2701,9 @@
 				    end >> agaw_to_width(si_domain->agaw)))
 				continue;
 
-			ret = iommu_domain_identity_map(si_domain, start, end);
+			ret = iommu_domain_identity_map(si_domain,
+					mm_to_dma_pfn(start >> PAGE_SHIFT),
+					mm_to_dma_pfn(end >> PAGE_SHIFT));
 			if (ret)
 				return ret;
 		}
@@ -6021,6 +6029,23 @@
 	return ret;
 }
 
+/*
+ * Check that the device does not live on an external facing PCI port that is
+ * marked as untrusted. Such devices should not be able to apply quirks and
+ * thus not be able to bypass the IOMMU restrictions.
+ */
+static bool risky_device(struct pci_dev *pdev)
+{
+	if (pdev->untrusted) {
+		pci_info(pdev,
+			 "Skipping IOMMU quirk for dev [%04X:%04X] on untrusted PCI link\n",
+			 pdev->vendor, pdev->device);
+		pci_info(pdev, "Please check with your BIOS/Platform vendor about this\n");
+		return true;
+	}
+	return false;
+}
+
 const struct iommu_ops intel_iommu_ops = {
 	.capable		= intel_iommu_capable,
 	.domain_alloc		= intel_iommu_domain_alloc,
@@ -6060,6 +6085,9 @@
 
 static void quirk_iommu_igfx(struct pci_dev *dev)
 {
+	if (risky_device(dev))
+		return;
+
 	pci_info(dev, "Disabling IOMMU for graphics on this chipset\n");
 	dmar_map_gfx = 0;
 }
@@ -6101,6 +6129,9 @@
 
 static void quirk_iommu_rwbf(struct pci_dev *dev)
 {
+	if (risky_device(dev))
+		return;
+
 	/*
 	 * Mobile 4 Series Chipset neglects to set RWBF capability,
 	 * but needs it. Same seems to hold for the desktop versions.
@@ -6131,6 +6162,9 @@
 {
 	unsigned short ggc;
 
+	if (risky_device(dev))
+		return;
+
 	if (pci_read_config_word(dev, GGC, &ggc))
 		return;
 
@@ -6164,6 +6198,12 @@
 	pdev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x3a3e, NULL);
 	if (!pdev)
 		return;
+
+	if (risky_device(pdev)) {
+		pci_dev_put(pdev);
+		return;
+	}
+
 	pci_dev_put(pdev);
 
 	/* System Management Registers. Might be hidden, in which case
@@ -6173,6 +6213,11 @@
 	if (!pdev)
 		return;
 
+	if (risky_device(pdev)) {
+		pci_dev_put(pdev);
+		return;
+	}
+
 	if (pci_read_config_dword(pdev, 0x188, &vtisochctrl)) {
 		pci_dev_put(pdev);
 		return;
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 4100bd2..3e8fa1c 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -41,6 +41,7 @@
 #define DMA_PTE_SNP		BIT_ULL(11)
 
 #define DMA_FL_PTE_PRESENT	BIT_ULL(0)
+#define DMA_FL_PTE_US		BIT_ULL(2)
 #define DMA_FL_PTE_XD		BIT_ULL(63)
 
 #define ADDR_WIDTH_5LEVEL	(57)