IOMMU Identity Mapping Support (drivers/pci/intel_iommu.c)

Identity mapping for IOMMU defines a single domain to 1:1 map all PCI
devices to all usable memory.

This reduces map/unmap overhead in DMA API's and improve IOMMU
performance. On 10Gb network cards, Netperf shows no performance
degradation compared to non-IOMMU performance.

This method may lose some of DMA remapping benefits like isolation.

The patch sets up identity mapping for all PCI devices to all usable
memory. In the DMA API, there is no overhead to maintain page tables,
invalidate iotlb, flush cache etc.

32 bit DMA devices don't use identity mapping domain, in order to access
memory beyond 4GiB.

When kernel option iommu=pt, pass through is first tried. If pass
through succeeds, IOMMU goes to pass through. If pass through is not
supported in hw or fail for whatever reason, IOMMU goes to identity
mapping.
Signed-off-by: NFenghua Yu <fenghua.yu@intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/pci/intel-iommu.c

@@ -39,6 +39,7 @@
 #include <linux/sysdev.h>
 #include <asm/cacheflush.h>
 #include <asm/iommu.h>
+#include <asm/e820.h>
 #include "pci.h"
 
 #define ROOT_SIZE		VTD_PAGE_SIZE
@@ -217,6 +218,14 @@ static inline bool dma_pte_present(struct dma_pte *pte)
 	return (pte->val & 3) != 0;
 }
 
+/*
+ * This domain is a statically identity mapping domain.
+ *	1. This domain creats a static 1:1 mapping to all usable memory.
+ * 	2. It maps to each iommu if successful.
+ *	3. Each iommu mapps to this domain if successful.
+ */
+struct dmar_domain *si_domain;
+
 /* devices under the same p2p bridge are owned in one domain */
 #define DOMAIN_FLAG_P2P_MULTIPLE_DEVICES (1 << 0)
 
@@ -225,6 +234,9 @@ static inline bool dma_pte_present(struct dma_pte *pte)
  */
 #define DOMAIN_FLAG_VIRTUAL_MACHINE	(1 << 1)
 
+/* si_domain contains mulitple devices */
+#define DOMAIN_FLAG_STATIC_IDENTITY	(1 << 2)
+
 struct dmar_domain {
 	int	id;			/* domain id */
 	unsigned long iommu_bmp;	/* bitmap of iommus this domain uses*/
@@ -435,12 +447,14 @@ int iommu_calculate_agaw(struct intel_iommu *iommu)
 	return __iommu_calculate_agaw(iommu, DEFAULT_DOMAIN_ADDRESS_WIDTH);
 }
 
-/* in native case, each domain is related to only one iommu */
+/* This functionin only returns single iommu in a domain */
 static struct intel_iommu *domain_get_iommu(struct dmar_domain *domain)
 {
 	int iommu_id;
 
+	/* si_domain and vm domain should not get here. */
 	BUG_ON(domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE);
+	BUG_ON(domain->flags & DOMAIN_FLAG_STATIC_IDENTITY);
 
 	iommu_id = find_first_bit(&domain->iommu_bmp, g_num_of_iommus);
 	if (iommu_id < 0 || iommu_id >= g_num_of_iommus)
@@ -1189,48 +1203,71 @@ void free_dmar_iommu(struct intel_iommu *iommu)
 	free_context_table(iommu);
 }
 
-static struct dmar_domain * iommu_alloc_domain(struct intel_iommu *iommu)
+static struct dmar_domain *alloc_domain(void)
 {
-	unsigned long num;
-	unsigned long ndomains;
 	struct dmar_domain *domain;
-	unsigned long flags;
 
 	domain = alloc_domain_mem();
 	if (!domain)
 		return NULL;
 
+	memset(&domain->iommu_bmp, 0, sizeof(unsigned long));
+	domain->flags = 0;
+
+	return domain;
+}
+
+static int iommu_attach_domain(struct dmar_domain *domain,
+			       struct intel_iommu *iommu)
+{
+	int num;
+	unsigned long ndomains;
+	unsigned long flags;
+
 	ndomains = cap_ndoms(iommu->cap);
 
 	spin_lock_irqsave(&iommu->lock, flags);
+
 	num = find_first_zero_bit(iommu->domain_ids, ndomains);
 	if (num >= ndomains) {
 		spin_unlock_irqrestore(&iommu->lock, flags);
-		free_domain_mem(domain);
 		printk(KERN_ERR "IOMMU: no free domain ids\n");
-		return NULL;
+		return -ENOMEM;
 	}
 
-	set_bit(num, iommu->domain_ids);
 	domain->id = num;
-	memset(&domain->iommu_bmp, 0, sizeof(unsigned long));
+	set_bit(num, iommu->domain_ids);
 	set_bit(iommu->seq_id, &domain->iommu_bmp);
-	domain->flags = 0;
 	iommu->domains[num] = domain;
 	spin_unlock_irqrestore(&iommu->lock, flags);
 
-	return domain;
+	return 0;
 }
 
-static void iommu_free_domain(struct dmar_domain *domain)
+static void iommu_detach_domain(struct dmar_domain *domain,
+				struct intel_iommu *iommu)
 {
 	unsigned long flags;
-	struct intel_iommu *iommu;
-
-	iommu = domain_get_iommu(domain);
+	int num, ndomains;
+	int found = 0;
 
 	spin_lock_irqsave(&iommu->lock, flags);
-	clear_bit(domain->id, iommu->domain_ids);
+	ndomains = cap_ndoms(iommu->cap);
+	num = find_first_bit(iommu->domain_ids, ndomains);
+	for (; num < ndomains; ) {
+		if (iommu->domains[num] == domain) {
+			found = 1;
+			break;
+		}
+		num = find_next_bit(iommu->domain_ids,
+				    cap_ndoms(iommu->cap), num+1);
+	}
+
+	if (found) {
+		clear_bit(num, iommu->domain_ids);
+		clear_bit(iommu->seq_id, &domain->iommu_bmp);
+		iommu->domains[num] = NULL;
+	}
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
@@ -1350,6 +1387,8 @@ static int domain_init(struct dmar_domain *domain, int guest_width)
 
 static void domain_exit(struct dmar_domain *domain)
 {
+	struct dmar_drhd_unit *drhd;
+	struct intel_iommu *iommu;
 	u64 end;
 
 	/* Domain 0 is reserved, so dont process it */
@@ -1368,7 +1407,10 @@ static void domain_exit(struct dmar_domain *domain)
 	/* free page tables */
 	dma_pte_free_pagetable(domain, 0, end);
 
-	iommu_free_domain(domain);
+	for_each_active_iommu(iommu, drhd)
+		if (test_bit(iommu->seq_id, &domain->iommu_bmp))
+			iommu_detach_domain(domain, iommu);
+
 	free_domain_mem(domain);
 }
 
@@ -1408,7 +1450,8 @@ static int domain_context_mapping_one(struct dmar_domain *domain, int segment,
 	id = domain->id;
 	pgd = domain->pgd;
 
-	if (domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE) {
+	if (domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE ||
+	    domain->flags & DOMAIN_FLAG_STATIC_IDENTITY) {
 		int found = 0;
 
 		/* find an available domain id for this device in iommu */
@@ -1433,6 +1476,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain, int segment,
 			}
 
 			set_bit(num, iommu->domain_ids);
+			set_bit(iommu->seq_id, &domain->iommu_bmp);
 			iommu->domains[num] = domain;
 			id = num;
 		}
@@ -1675,6 +1719,7 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 	unsigned long flags;
 	int bus = 0, devfn = 0;
 	int segment;
+	int ret;
 
 	domain = find_domain(pdev);
 	if (domain)
@@ -1707,6 +1752,10 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 		}
 	}
 
+	domain = alloc_domain();
+	if (!domain)
+		goto error;
+
 	/* Allocate new domain for the device */
 	drhd = dmar_find_matched_drhd_unit(pdev);
 	if (!drhd) {
@@ -1716,9 +1765,11 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 	}
 	iommu = drhd->iommu;
 
-	domain = iommu_alloc_domain(iommu);
-	if (!domain)
+	ret = iommu_attach_domain(domain, iommu);
+	if (ret) {
+		domain_exit(domain);
 		goto error;
+	}
 
 	if (domain_init(domain, gaw)) {
 		domain_exit(domain);
@@ -1792,6 +1843,8 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 	return find_domain(pdev);
 }
 
+static int iommu_identity_mapping;
+
 static int iommu_prepare_identity_map(struct pci_dev *pdev,
 				      unsigned long long start,
 				      unsigned long long end)
@@ -1804,8 +1857,11 @@ static int iommu_prepare_identity_map(struct pci_dev *pdev,
 	printk(KERN_INFO
 		"IOMMU: Setting identity map for device %s [0x%Lx - 0x%Lx]\n",
 		pci_name(pdev), start, end);
-	/* page table init */
-	domain = get_domain_for_dev(pdev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
+	if (iommu_identity_mapping)
+		domain = si_domain;
+	else
+		/* page table init */
+		domain = get_domain_for_dev(pdev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
 	if (!domain)
 		return -ENOMEM;
 
@@ -1952,7 +2008,110 @@ static int __init init_context_pass_through(void)
 	return 0;
 }
 
-static int __init init_dmars(void)
+static int md_domain_init(struct dmar_domain *domain, int guest_width);
+static int si_domain_init(void)
+{
+	struct dmar_drhd_unit *drhd;
+	struct intel_iommu *iommu;
+	int ret = 0;
+
+	si_domain = alloc_domain();
+	if (!si_domain)
+		return -EFAULT;
+
+
+	for_each_active_iommu(iommu, drhd) {
+		ret = iommu_attach_domain(si_domain, iommu);
+		if (ret) {
+			domain_exit(si_domain);
+			return -EFAULT;
+		}
+	}
+
+	if (md_domain_init(si_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
+		domain_exit(si_domain);
+		return -EFAULT;
+	}
+
+	si_domain->flags = DOMAIN_FLAG_STATIC_IDENTITY;
+
+	return 0;
+}
+
+static void domain_remove_one_dev_info(struct dmar_domain *domain,
+					  struct pci_dev *pdev);
+static int identity_mapping(struct pci_dev *pdev)
+{
+	struct device_domain_info *info;
+
+	if (likely(!iommu_identity_mapping))
+		return 0;
+
+
+	list_for_each_entry(info, &si_domain->devices, link)
+		if (info->dev == pdev)
+			return 1;
+	return 0;
+}
+
+static int domain_add_dev_info(struct dmar_domain *domain,
+				  struct pci_dev *pdev)
+{
+	struct device_domain_info *info;
+	unsigned long flags;
+
+	info = alloc_devinfo_mem();
+	if (!info)
+		return -ENOMEM;
+
+	info->segment = pci_domain_nr(pdev->bus);
+	info->bus = pdev->bus->number;
+	info->devfn = pdev->devfn;
+	info->dev = pdev;
+	info->domain = domain;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	list_add(&info->link, &domain->devices);
+	list_add(&info->global, &device_domain_list);
+	pdev->dev.archdata.iommu = info;
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+
+	return 0;
+}
+
+static int iommu_prepare_static_identity_mapping(void)
+{
+	int i;
+	struct pci_dev *pdev = NULL;
+	int ret;
+
+	ret = si_domain_init();
+	if (ret)
+		return -EFAULT;
+
+	printk(KERN_INFO "IOMMU: Setting identity map:\n");
+	for_each_pci_dev(pdev) {
+		for (i = 0; i < e820.nr_map; i++) {
+			struct e820entry *ei = &e820.map[i];
+
+			if (ei->type == E820_RAM) {
+				ret = iommu_prepare_identity_map(pdev,
+					ei->addr, ei->addr + ei->size);
+				if (ret)  {
+					printk(KERN_INFO "1:1 mapping to one domain failed.\n");
+					return -EFAULT;
+				}
+			}
+		}
+		ret = domain_add_dev_info(si_domain, pdev);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+int __init init_dmars(void)
 {
 	struct dmar_drhd_unit *drhd;
 	struct dmar_rmrr_unit *rmrr;
@@ -1961,6 +2120,13 @@ static int __init init_dmars(void)
 	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
 	 *    allocate root
@@ -2090,9 +2256,12 @@ static int __init init_dmars(void)
 
 	/*
 	 * If pass through is not set or not enabled, setup context entries for
-	 * identity mappings for rmrr, gfx, and isa.
+	 * 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) {
+		if (iommu_identity_mapping)
+			iommu_prepare_static_identity_mapping();
 		/*
 		 * For each rmrr
 		 *   for each dev attached to rmrr
@@ -2107,6 +2276,7 @@ static int __init init_dmars(void)
 		 *    endfor
 		 * endfor
 		 */
+		printk(KERN_INFO "IOMMU: Setting RMRR:\n");
 		for_each_rmrr_units(rmrr) {
 			for (i = 0; i < rmrr->devices_cnt; i++) {
 				pdev = rmrr->devices[i];
@@ -2248,6 +2418,52 @@ get_valid_domain_for_dev(struct pci_dev *pdev)
 	return domain;
 }
 
+static int iommu_dummy(struct pci_dev *pdev)
+{
+	return pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO;
+}
+
+/* Check if the pdev needs to go through non-identity map and unmap process.*/
+static int iommu_no_mapping(struct pci_dev *pdev)
+{
+	int found;
+
+	if (!iommu_identity_mapping)
+		return iommu_dummy(pdev);
+
+	found = identity_mapping(pdev);
+	if (found) {
+		if (pdev->dma_mask > DMA_BIT_MASK(32))
+			return 1;
+		else {
+			/*
+			 * 32 bit DMA is removed from si_domain and fall back
+			 * to non-identity mapping.
+			 */
+			domain_remove_one_dev_info(si_domain, pdev);
+			printk(KERN_INFO "32bit %s uses non-identity mapping\n",
+			       pci_name(pdev));
+			return 0;
+		}
+	} else {
+		/*
+		 * In case of a detached 64 bit DMA device from vm, the device
+		 * is put into si_domain for identity mapping.
+		 */
+		if (pdev->dma_mask > DMA_BIT_MASK(32)) {
+			int ret;
+			ret = domain_add_dev_info(si_domain, pdev);
+			if (!ret) {
+				printk(KERN_INFO "64bit %s uses identity mapping\n",
+				       pci_name(pdev));
+				return 1;
+			}
+		}
+	}
+
+	return iommu_dummy(pdev);
+}
+
 static dma_addr_t __intel_map_single(struct device *hwdev, phys_addr_t paddr,
 				     size_t size, int dir, u64 dma_mask)
 {
@@ -2260,7 +2476,8 @@ static dma_addr_t __intel_map_single(struct device *hwdev, phys_addr_t paddr,
 	struct intel_iommu *iommu;
 
 	BUG_ON(dir == DMA_NONE);
-	if (pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO)
+
+	if (iommu_no_mapping(pdev))
 		return paddr;
 
 	domain = get_valid_domain_for_dev(pdev);
@@ -2401,8 +2618,9 @@ static void intel_unmap_page(struct device *dev, dma_addr_t dev_addr,
 	struct iova *iova;
 	struct intel_iommu *iommu;
 
-	if (pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO)
+	if (iommu_no_mapping(pdev))
 		return;
+
 	domain = find_domain(pdev);
 	BUG_ON(!domain);
 
@@ -2492,7 +2710,7 @@ static void intel_unmap_sg(struct device *hwdev, struct scatterlist *sglist,
 	struct scatterlist *sg;
 	struct intel_iommu *iommu;
 
-	if (pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO)
+	if (iommu_no_mapping(pdev))
 		return;
 
 	domain = find_domain(pdev);
@@ -2553,7 +2771,7 @@ static int intel_map_sg(struct device *hwdev, struct scatterlist *sglist, int ne
 	struct intel_iommu *iommu;
 
 	BUG_ON(dir == DMA_NONE);
-	if (pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO)
+	if (iommu_no_mapping(pdev))
 		return intel_nontranslate_map_sg(hwdev, sglist, nelems, dir);
 
 	domain = get_valid_domain_for_dev(pdev);
@@ -2951,31 +3169,6 @@ int __init intel_iommu_init(void)
 	return 0;
 }
 
-static int vm_domain_add_dev_info(struct dmar_domain *domain,
-				  struct pci_dev *pdev)
-{
-	struct device_domain_info *info;
-	unsigned long flags;
-
-	info = alloc_devinfo_mem();
-	if (!info)
-		return -ENOMEM;
-
-	info->segment = pci_domain_nr(pdev->bus);
-	info->bus = pdev->bus->number;
-	info->devfn = pdev->devfn;
-	info->dev = pdev;
-	info->domain = domain;
-
-	spin_lock_irqsave(&device_domain_lock, flags);
-	list_add(&info->link, &domain->devices);
-	list_add(&info->global, &device_domain_list);
-	pdev->dev.archdata.iommu = info;
-	spin_unlock_irqrestore(&device_domain_lock, flags);
-
-	return 0;
-}
-
 static void iommu_detach_dependent_devices(struct intel_iommu *iommu,
 					   struct pci_dev *pdev)
 {
@@ -3003,7 +3196,7 @@ static void iommu_detach_dependent_devices(struct intel_iommu *iommu,
 	}
 }
 
-static void vm_domain_remove_one_dev_info(struct dmar_domain *domain,
+static void domain_remove_one_dev_info(struct dmar_domain *domain,
 					  struct pci_dev *pdev)
 {
 	struct device_domain_info *info;
@@ -3136,7 +3329,7 @@ static struct dmar_domain *iommu_alloc_vm_domain(void)
 	return domain;
 }
 
-static int vm_domain_init(struct dmar_domain *domain, int guest_width)
+static int md_domain_init(struct dmar_domain *domain, int guest_width)
 {
 	int adjust_width;
 
@@ -3227,7 +3420,7 @@ static int intel_iommu_domain_init(struct iommu_domain *domain)
 			"intel_iommu_domain_init: dmar_domain == NULL\n");
 		return -ENOMEM;
 	}
-	if (vm_domain_init(dmar_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
+	if (md_domain_init(dmar_domain, DEFAULT_DOMAIN_ADDRESS_WIDTH)) {
 		printk(KERN_ERR
 			"intel_iommu_domain_init() failed\n");
 		vm_domain_exit(dmar_domain);
@@ -3262,8 +3455,9 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 
 		old_domain = find_domain(pdev);
 		if (old_domain) {
-			if (dmar_domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE)
-				vm_domain_remove_one_dev_info(old_domain, pdev);
+			if (dmar_domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE ||
+			    dmar_domain->flags & DOMAIN_FLAG_STATIC_IDENTITY)
+				domain_remove_one_dev_info(old_domain, pdev);
 			else
 				domain_remove_dev_info(old_domain);
 		}
@@ -3285,7 +3479,7 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 		return -EFAULT;
 	}
 
-	ret = vm_domain_add_dev_info(dmar_domain, pdev);
+	ret = domain_add_dev_info(dmar_domain, pdev);
 	if (ret)
 		return ret;
 
@@ -3299,7 +3493,7 @@ static void intel_iommu_detach_device(struct iommu_domain *domain,
 	struct dmar_domain *dmar_domain = domain->priv;
 	struct pci_dev *pdev = to_pci_dev(dev);
 
-	vm_domain_remove_one_dev_info(dmar_domain, pdev);
+	domain_remove_one_dev_info(dmar_domain, pdev);
 }
 
 static int intel_iommu_map_range(struct iommu_domain *domain,