#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
        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)
 
  */
 #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*/
        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)
        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);
 }
 
 
 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 */
        /* 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);
 }
 
        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 */
                        }
 
                        set_bit(num, iommu->domain_ids);
+                       set_bit(iommu->seq_id, &domain->iommu_bmp);
                        iommu->domains[num] = domain;
                        id = num;
                }
        unsigned long flags;
        int bus = 0, devfn = 0;
        int segment;
+       int ret;
 
        domain = find_domain(pdev);
        if (domain)
                }
        }
 
+       domain = alloc_domain();
+       if (!domain)
+               goto error;
+
        /* Allocate new domain for the device */
        drhd = dmar_find_matched_drhd_unit(pdev);
        if (!drhd) {
        }
        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);
        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)
        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;
 
        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;
        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
 
        /*
         * 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
                 *    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];
        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)
 {
        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);
        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);
 
        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);
        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);
        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)
 {
        }
 }
 
-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;
        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;
 
                        "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);
 
                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);
                }
                return -EFAULT;
        }
 
-       ret = vm_domain_add_dev_info(dmar_domain, pdev);
+       ret = domain_add_dev_info(dmar_domain, pdev);
        if (ret)
                return ret;
 
        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,