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: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 74 insertions, 100 deletions

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 097d5da2fae1..147b3b960b61 100644
--- a/drivers/pci/intel-iommu.c
+++ b/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
@@ -2250,14 +2241,8 @@ int __init init_dmars(void)
                         goto error;
                 }
                 if (!ecap_pass_through(iommu->ecap))
-                        pass_through = 0;
+                        hw_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;
-                }
 
         /*
          * Start from the sane iommu hardware state.
@@ -2312,64 +2297,57 @@ int __init init_dmars(void)
                 }
         }
 
+        if (iommu_pass_through)
+                iommu_identity_mapping = 1;
+#ifdef CONFIG_DMAR_BROKEN_GFX_WA
+        else
+                iommu_identity_mapping = 2;
+#endif
         /*
-         * If pass through is set and enabled, context entries of all pci
-         * devices are intialized by pass through translation type.
+         * 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) {
-                ret = init_context_pass_through();
+        if (iommu_identity_mapping) {
+                ret = iommu_prepare_static_identity_mapping(hw_pass_through);
                 if (ret) {
-                        printk(KERN_ERR "IOMMU: Pass through init failed.\n");
-                        iommu_pass_through = 0;
+                        printk(KERN_CRIT "Failed to setup IOMMU pass-through\n");
+                        goto error;
                 }
         }
-
         /*
-         * 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.
+         * For each rmrr
+         *   for each dev attached to rmrr
+         *   do
+         *     locate drhd for dev, alloc domain for dev
+         *     allocate free domain
+         *     allocate page table entries for rmrr
+         *     if context not allocated for bus
+         *           allocate and init context
+         *           set present in root table for this bus
+         *     init context with domain, translation etc
+         *    endfor
+         * endfor
          */
-        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();
-                /*
-                 * For each rmrr
-                 *   for each dev attached to rmrr
-                 *   do
-                 *     locate drhd for dev, alloc domain for dev
-                 *     allocate free domain
-                 *     allocate page table entries for rmrr
-                 *     if context not allocated for bus
-                 *           allocate and init context
-                 *           set present in root table for this bus
-                 *     init context with domain, translation etc
-                 *    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];
-                                /*
-                                 * some BIOS lists non-exist devices in DMAR
-                                 * table.
-                                 */
-                                if (!pdev)
-                                        continue;
-                                ret = iommu_prepare_rmrr_dev(rmrr, pdev);
-                                if (ret)
-                                        printk(KERN_ERR
-                                 "IOMMU: mapping reserved region failed\n");
-                        }
+        printk(KERN_INFO "IOMMU: Setting RMRR:\n");
+        for_each_rmrr_units(rmrr) {
+                for (i = 0; i < rmrr->devices_cnt; i++) {
+                        pdev = rmrr->devices[i];
+                        /*
+                         * some BIOS lists non-exist devices in DMAR
+                         * table.
+                         */
+                        if (!pdev)
+                                continue;
+                        ret = iommu_prepare_rmrr_dev(rmrr, pdev);
+                        if (ret)
+                                printk(KERN_ERR
+                                       "IOMMU: mapping reserved region failed\n");
                 }
-
-                iommu_prepare_isa();
         }
 
+        iommu_prepare_isa();
+
         /*
          * for each drhd
          *   enable fault log
@@ -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");
+        dma_ops = &intel_dma_ops;
 
         init_iommu_sysfs();