intel-iommu: Unify hardware and software passthrough support

This makes the hardware passthrough mode work a lot more like the
software version, so that the behaviour of a kernel with 'iommu=pt'
is the same whether the hardware supports passthrough or not.

In particular:
 - We use a single si_domain for the pass-through devices.
 - 32-bit devices can be taken out of the pass-through domain so that
   they don't have to use swiotlb.
 - Devices will work again after being removed from a KVM guest.
 - A potential oops on OOM (in init_context_pass_through()) is fixed.
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

arch/x86/kernel/pci-swiotlb.c

@@ -71,8 +71,7 @@ void __init pci_swiotlb_init(void)
 {
 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
 #ifdef CONFIG_X86_64
-	if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) ||
-		iommu_pass_through)
+	if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN))
 		swiotlb = 1;
 #endif
 	if (swiotlb_force)

drivers/pci/intel-iommu.c

@@ -251,7 +251,8 @@ static inline int first_pte_in_page(struct dma_pte *pte)
  * 	2. It maps to each iommu if successful.
  *	3. Each iommu mapps to this domain if successful.
  */
-struct dmar_domain *si_domain;
+static struct dmar_domain *si_domain;
+static int hw_pass_through = 1;
 
 /* devices under the same p2p bridge are owned in one domain */
 #define DOMAIN_FLAG_P2P_MULTIPLE_DEVICES (1 << 0)
@@ -1948,14 +1949,24 @@ static int iommu_prepare_identity_map(struct pci_dev *pdev,
 	struct dmar_domain *domain;
 	int ret;
 
-	printk(KERN_INFO
-	       "IOMMU: Setting identity map for device %s [0x%Lx - 0x%Lx]\n",
-	       pci_name(pdev), start, end);
-
 	domain = get_domain_for_dev(pdev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
 	if (!domain)
 		return -ENOMEM;
 
+	/* For _hardware_ passthrough, don't bother. But for software
+	   passthrough, we do it anyway -- it may indicate a memory
+	   range which is reserved in E820, so which didn't get set
+	   up to start with in si_domain */
+	if (domain == si_domain && hw_pass_through) {
+		printk("Ignoring identity map for HW passthrough device %s [0x%Lx - 0x%Lx]\n",
+		       pci_name(pdev), start, end);
+		return 0;
+	}
+
+	printk(KERN_INFO
+	       "IOMMU: Setting identity map for device %s [0x%Lx - 0x%Lx]\n",
+	       pci_name(pdev), start, end);
+
 	ret = iommu_domain_identity_map(domain, start, end);
 	if (ret)
 		goto error;
@@ -2006,23 +2017,6 @@ static inline void iommu_prepare_isa(void)
 }
 #endif /* !CONFIG_DMAR_FLPY_WA */
 
-/* Initialize each context entry as pass through.*/
-static int __init init_context_pass_through(void)
-{
-	struct pci_dev *pdev = NULL;
-	struct dmar_domain *domain;
-	int ret;
-
-	for_each_pci_dev(pdev) {
-		domain = get_domain_for_dev(pdev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
-		ret = domain_context_mapping(domain, pdev,
-					     CONTEXT_TT_PASS_THROUGH);
-		if (ret)
-			return ret;
-	}
-	return 0;
-}
-
 static int md_domain_init(struct dmar_domain *domain, int guest_width);
 
 static int __init si_domain_work_fn(unsigned long start_pfn,
@@ -2037,7 +2031,7 @@ static int __init si_domain_work_fn(unsigned long start_pfn,
 
 }
 
-static int si_domain_init(void)
+static int si_domain_init(int hw)
 {
 	struct dmar_drhd_unit *drhd;
 	struct intel_iommu *iommu;
@@ -2064,6 +2058,9 @@ static int si_domain_init(void)
 
 	si_domain->flags = DOMAIN_FLAG_STATIC_IDENTITY;
 
+	if (hw)
+		return 0;
+
 	for_each_online_node(nid) {
 		work_with_active_regions(nid, si_domain_work_fn, &ret);
 		if (ret)
@@ -2155,24 +2152,26 @@ static int iommu_should_identity_map(struct pci_dev *pdev, int startup)
 	return 1;
 }
 
-static int iommu_prepare_static_identity_mapping(void)
+static int iommu_prepare_static_identity_mapping(int hw)
 {
 	struct pci_dev *pdev = NULL;
 	int ret;
 
-	ret = si_domain_init();
+	ret = si_domain_init(hw);
 	if (ret)
 		return -EFAULT;
 
 	for_each_pci_dev(pdev) {
 		if (iommu_should_identity_map(pdev, 1)) {
-			printk(KERN_INFO "IOMMU: identity mapping for device %s\n",
-			       pci_name(pdev));
+			printk(KERN_INFO "IOMMU: %s identity mapping for device %s\n",
+			       hw ? "hardware" : "software", pci_name(pdev));
 
 			ret = domain_context_mapping(si_domain, pdev,
+						     hw ? CONTEXT_TT_PASS_THROUGH :
 						     CONTEXT_TT_MULTI_LEVEL);
 			if (ret)
 				return ret;
+
 			ret = domain_add_dev_info(si_domain, pdev);
 			if (ret)
 				return ret;
@@ -2189,14 +2188,6 @@ int __init init_dmars(void)
 	struct pci_dev *pdev;
 	struct intel_iommu *iommu;
 	int i, ret;
-	int pass_through = 1;
-
-	/*
-	 * In case pass through can not be enabled, iommu tries to use identity
-	 * mapping.
-	 */
-	if (iommu_pass_through)
-		iommu_identity_mapping = 1;
 
 	/*
 	 * for each drhd
@@ -2250,13 +2241,7 @@ int __init init_dmars(void)
 			goto error;
 		}
 		if (!ecap_pass_through(iommu->ecap))
-			pass_through = 0;
-	}
-	if (iommu_pass_through)
-		if (!pass_through) {
-			printk(KERN_INFO
-			       "Pass Through is not supported by hardware.\n");
-			iommu_pass_through = 0;
+			hw_pass_through = 0;
 	}
 
 	/*
@@ -2312,30 +2297,24 @@ int __init init_dmars(void)
 		}
 	}
 
-	/*
-	 * If pass through is set and enabled, context entries of all pci
-	 * devices are intialized by pass through translation type.
-	 */
-	if (iommu_pass_through) {
-		ret = init_context_pass_through();
-		if (ret) {
-			printk(KERN_ERR "IOMMU: Pass through init failed.\n");
-			iommu_pass_through = 0;
-		}
-	}
-
+	if (iommu_pass_through)
+		iommu_identity_mapping = 1;
+#ifdef CONFIG_DMAR_BROKEN_GFX_WA
+	else
+		iommu_identity_mapping = 2;
+#endif
 	/*
 	 * If pass through is not set or not enabled, setup context entries for
 	 * identity mappings for rmrr, gfx, and isa and may fall back to static
 	 * identity mapping if iommu_identity_mapping is set.
 	 */
-	if (!iommu_pass_through) {
-#ifdef CONFIG_DMAR_BROKEN_GFX_WA
-		if (!iommu_identity_mapping)
-			iommu_identity_mapping = 2;
-#endif
-		if (iommu_identity_mapping)
-			iommu_prepare_static_identity_mapping();
+	if (iommu_identity_mapping) {
+		ret = iommu_prepare_static_identity_mapping(hw_pass_through);
+		if (ret) {
+			printk(KERN_CRIT "Failed to setup IOMMU pass-through\n");
+			goto error;
+		}
+	}
 	/*
 	 * For each rmrr
 	 *   for each dev attached to rmrr
@@ -2368,7 +2347,6 @@ int __init init_dmars(void)
 	}
 
 	iommu_prepare_isa();
-	}
 
 	/*
 	 * for each drhd
@@ -2536,7 +2514,10 @@ static int iommu_no_mapping(struct device *dev)
 			ret = domain_add_dev_info(si_domain, pdev);
 			if (ret)
 				return 0;
-			ret = domain_context_mapping(si_domain, pdev, CONTEXT_TT_MULTI_LEVEL);
+			ret = domain_context_mapping(si_domain, pdev,
+						     hw_pass_through ?
+						     CONTEXT_TT_PASS_THROUGH :
+						     CONTEXT_TT_MULTI_LEVEL);
 			if (!ret) {
 				printk(KERN_INFO "64bit %s uses identity mapping\n",
 				       pci_name(pdev));
@@ -3202,7 +3183,7 @@ int __init intel_iommu_init(void)
 	 * Check the need for DMA-remapping initialization now.
 	 * Above initialization will also be used by Interrupt-remapping.
 	 */
-	if (no_iommu || (swiotlb && !iommu_pass_through) || dmar_disabled)
+	if (no_iommu || swiotlb || dmar_disabled)
 		return -ENODEV;
 
 	iommu_init_mempool();
@@ -3222,14 +3203,7 @@ int __init intel_iommu_init(void)
 
 	init_timer(&unmap_timer);
 	force_iommu = 1;
-
-	if (!iommu_pass_through) {
-		printk(KERN_INFO
-		       "Multi-level page-table translation for DMAR.\n");
 	dma_ops = &intel_dma_ops;
-	} else
-		printk(KERN_INFO
-		       "DMAR: Pass through translation for DMAR.\n");
 
 	init_iommu_sysfs();