[PATCH 0/2] Make the vmwgfx driver reasonably DMA-API compliant

[PATCH 0/2] Make the vmwgfx driver reasonably DMA-API compliant

[Thomas Hellstrom]

These patches makes the vmwgfx driver use the DMA API to obtain valid
device addresses rather than blindly using physical addresses.

The main motivation is to be able to use a virtual IOMMU in the future.

Other TTM drivers typically map pages one by one rather than using a
scatter-gather list, but since we can benefit from having a single dma
address region set up by the IOMMU, we use a scatter-gather list instead.

Finally to be able to handle all the dma mapping modes, we locally extend the
scatter-gather list page iterator to handle also the direct physical- and
coherent cases.

Finally, the TTM DMA page pool is enabled also when the Intel IOMMU is active

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[PATCH 1/2] drm/ttm: Enable the dma page pool also for intel IOMMUs

[Thomas Hellstrom]

Used by the vmwgfx driver

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
---
 drivers/gpu/drm/ttm/Makefile             |    6 +-----
 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c |    3 +++
 include/drm/ttm/ttm_page_alloc.h         |   11 ++++++++++-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
index b2b33dd..b433b9f 100644
--- a/drivers/gpu/drm/ttm/Makefile
+++ b/drivers/gpu/drm/ttm/Makefile
@@ -5,10 +5,6 @@ ccflags-y := -Iinclude/drm
 ttm-y := ttm_agp_backend.o ttm_memory.o ttm_tt.o ttm_bo.o \
 	ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
 	ttm_object.o ttm_lock.o ttm_execbuf_util.o ttm_page_alloc.o \
-	ttm_bo_manager.o
-
-ifeq ($(CONFIG_SWIOTLB),y)
-ttm-y += ttm_page_alloc_dma.o
-endif
+	ttm_bo_manager.o ttm_page_alloc_dma.o
 
 obj-$(CONFIG_DRM_TTM) += ttm.o
diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index 7957bee..fb8259f 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -33,6 +33,7 @@
  *   when freed).
  */
 
+#if defined(CONFIG_SWIOTLB) || defined(CONFIG_INTEL_IOMMU)
 #define pr_fmt(fmt) "[TTM] " fmt
 
 #include <linux/dma-mapping.h>
@@ -1142,3 +1143,5 @@ int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ttm_dma_page_alloc_debugfs);
+
+#endif
diff --git a/include/drm/ttm/ttm_page_alloc.h b/include/drm/ttm/ttm_page_alloc.h
index 706b962..d1f61bf 100644
--- a/include/drm/ttm/ttm_page_alloc.h
+++ b/include/drm/ttm/ttm_page_alloc.h
@@ -62,7 +62,7 @@ extern void ttm_pool_unpopulate(struct ttm_tt *ttm);
 extern int ttm_page_alloc_debugfs(struct seq_file *m, void *data);
 
 
-#ifdef CONFIG_SWIOTLB
+#if defined(CONFIG_SWIOTLB) || defined(CONFIG_INTEL_IOMMU)
 /**
  * Initialize pool allocator.
  */
@@ -94,6 +94,15 @@ static inline int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data)
 {
 	return 0;
 }
+static inline int ttm_dma_populate(struct ttm_dma_tt *ttm_dma,
+				   struct device *dev)
+{
+	return -ENOMEM;
+}
+static inline void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma,
+				      struct device *dev)
+{
+}
 #endif
 
 #endif
-- 
1.7.10.4

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[PATCH 2/2] drm/vmwgfx: Use the linux DMA api to get valid device addresses of pages

[Thomas Hellstrom]

The code handles three different cases:
1) physical page addresses. The ttm page array is used.
2) DMA subsystem addresses. A scatter-gather list is used.
3) Coherent pages. The ttm dma pool is used, together with the dma_ttm
array os dma_addr_t

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c |  379 ++++++++++++++++++++++++++++++--
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    |   87 +++++++-
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.h    |   98 ++++++++-
 drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c    |  150 ++++++-------
 4 files changed, 620 insertions(+), 94 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
index 96dc84d..7776e6f 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
@@ -141,37 +141,374 @@ struct ttm_placement vmw_srf_placement = {
 };
 
 struct vmw_ttm_tt {
-	struct ttm_tt ttm;
+	struct ttm_dma_tt dma_ttm;
 	struct vmw_private *dev_priv;
 	int gmr_id;
+	struct sg_table sgt;
+	struct vmw_sg_table vsgt;
+	uint64_t sg_alloc_size;
+	bool mapped;
 };
 
+/**
+ * Helper functions to advance a struct vmw_piter iterator.
+ *
+ * @viter: Pointer to the iterator.
+ *
+ * These functions return false if past the end of the list,
+ * true otherwise. Functions are selected depending on the current
+ * DMA mapping mode.
+ */
+static bool __vmw_piter_non_sg_next(struct vmw_piter *viter)
+{
+	return ++(viter->i) < viter->num_pages;
+}
+
+static bool __vmw_piter_sg_next(struct vmw_piter *viter)
+{
+	return __sg_page_iter_next(&viter->iter);
+}
+
+
+/**
+ * Helper functions to return a pointer to the current page.
+ *
+ * @viter: Pointer to the iterator
+ *
+ * These functions return a pointer to the page currently
+ * pointed to by @viter. Functions are selected depending on the
+ * current mapping mode.
+ */
+static struct page *__vmw_piter_non_sg_page(struct vmw_piter *viter)
+{
+	return viter->pages[viter->i];
+}
+
+static struct page *__vmw_piter_sg_page(struct vmw_piter *viter)
+{
+	return sg_page_iter_page(&viter->iter);
+}
+
+
+/**
+ * Helper functions to return the DMA address of the current page.
+ *
+ * @viter: Pointer to the iterator
+ *
+ * These functions return the DMA address of the page currently
+ * pointed to by @viter. Functions are selected depending on the
+ * current mapping mode.
+ */
+static dma_addr_t __vmw_piter_phys_addr(struct vmw_piter *viter)
+{
+	return page_to_phys(viter->pages[viter->i]);
+}
+
+static dma_addr_t __vmw_piter_dma_addr(struct vmw_piter *viter)
+{
+	return viter->addrs[viter->i];
+}
+
+static dma_addr_t __vmw_piter_sg_addr(struct vmw_piter *viter)
+{
+	return sg_page_iter_dma_address(&viter->iter);
+}
+
+
+/**
+ * vmw_piter_start - Initialize a struct vmw_piter.
+ *
+ * @viter: Pointer to the iterator to initialize
+ * @vsgt: Pointer to a struct vmw_sg_table to initialize from
+ *
+ * Note that we're following the convention of __sg_page_iter_start, so that
+ * the iterator doesn't point to a valid page after initialization; it has
+ * to be advanced one step first.
+ */
+void vmw_piter_start(struct vmw_piter *viter, const struct vmw_sg_table *vsgt,
+		     unsigned long p_offset)
+{
+	viter->i = p_offset - 1;
+	viter->num_pages = vsgt->num_pages;
+	switch (vsgt->mode) {
+	case vmw_dma_phys:
+		viter->next = &__vmw_piter_non_sg_next;
+		viter->dma_address = &__vmw_piter_phys_addr;
+		viter->page = &__vmw_piter_non_sg_page;
+		viter->pages = vsgt->pages;
+		break;
+	case vmw_dma_alloc_coherent:
+		viter->next = &__vmw_piter_non_sg_next;
+		viter->dma_address = &__vmw_piter_dma_addr;
+		viter->page = &__vmw_piter_non_sg_page;
+		viter->addrs = vsgt->addrs;
+		break;
+	case vmw_dma_map_populate:
+	case vmw_dma_map_bind:
+		viter->next = &__vmw_piter_sg_next;
+		viter->dma_address = &__vmw_piter_sg_addr;
+		viter->page = &__vmw_piter_sg_page;
+		__sg_page_iter_start(&viter->iter, vsgt->sgt->sgl,
+				     vsgt->sgt->orig_nents, p_offset);
+		break;
+	default:
+		BUG();
+	}
+}
+
+/**
+ * vmw_ttm_unmap_from_dma - unmap  device addresses previsouly mapped for
+ * TTM pages
+ *
+ * @vmw_tt: Pointer to a struct vmw_ttm_backend
+ *
+ * Used to free dma mappings previously mapped by vmw_ttm_map_for_dma.
+ */
+static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt)
+{
+	struct device *dev = vmw_tt->dev_priv->dev->dev;
+
+	dma_unmap_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.nents,
+		DMA_BIDIRECTIONAL);
+	vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents;
+}
+
+/**
+ * vmw_ttm_map_for_dma - map TTM pages to get device addresses
+ *
+ * @vmw_tt: Pointer to a struct vmw_ttm_backend
+ *
+ * This function is used to get device addresses from the kernel DMA layer.
+ * However, it's violating the DMA API in that when this operation has been
+ * performed, it's illegal for the CPU to write to the pages without first
+ * unmapping the DMA mappings, or calling dma_sync_sg_for_cpu(). It is
+ * therefore only legal to call this function if we know that the function
+ * dma_sync_sg_for_cpu() is a NOP, and dma_sync_sg_for_device() is at most
+ * a CPU write buffer flush.
+ */
+static int vmw_ttm_map_for_dma(struct vmw_ttm_tt *vmw_tt)
+{
+	struct device *dev = vmw_tt->dev_priv->dev->dev;
+	int ret;
+
+	ret = dma_map_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.orig_nents,
+			 DMA_BIDIRECTIONAL);
+	if (unlikely(ret == 0))
+		return -ENOMEM;
+
+	vmw_tt->sgt.nents = ret;
+
+	return 0;
+}
+
+/**
+ * vmw_ttm_map_dma - Make sure TTM pages are visible to the device
+ *
+ * @vmw_tt: Pointer to a struct vmw_ttm_tt
+ *
+ * Select the correct function for and make sure the TTM pages are
+ * visible to the device. Allocate storage for the device mappings.
+ * If a mapping has already been performed, indicated by the storage
+ * pointer being non NULL, the function returns success.
+ */
+static int vmw_ttm_map_dma(struct vmw_ttm_tt *vmw_tt)
+{
+	struct vmw_private *dev_priv = vmw_tt->dev_priv;
+	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
+	struct vmw_sg_table *vsgt = &vmw_tt->vsgt;
+	struct vmw_piter iter;
+	dma_addr_t old;
+	int ret = 0;
+	static size_t sgl_size;
+	static size_t sgt_size;
+
+	if (vmw_tt->mapped)
+		return 0;
+
+	vsgt->mode = dev_priv->map_mode;
+	vsgt->pages = vmw_tt->dma_ttm.ttm.pages;
+	vsgt->num_pages = vmw_tt->dma_ttm.ttm.num_pages;
+	vsgt->addrs = vmw_tt->dma_ttm.dma_address;
+	vsgt->sgt = &vmw_tt->sgt;
+
+	switch (dev_priv->map_mode) {
+	case vmw_dma_map_bind:
+	case vmw_dma_map_populate:
+		if (unlikely(!sgl_size)) {
+			sgl_size = ttm_round_pot(sizeof(struct scatterlist));
+			sgt_size = ttm_round_pot(sizeof(struct sg_table));
+		}
+		vmw_tt->sg_alloc_size = sgt_size + sgl_size * vsgt->num_pages;
+		ret = ttm_mem_global_alloc(glob, vmw_tt->sg_alloc_size, false,
+					   true);
+		if (unlikely(ret != 0))
+			return ret;
+
+		ret = sg_alloc_table_from_pages(&vmw_tt->sgt, vsgt->pages,
+						vsgt->num_pages, 0,
+						(unsigned long)
+						vsgt->num_pages << PAGE_SHIFT,
+						GFP_KERNEL);
+		if (unlikely(ret != 0))
+			goto out_sg_alloc_fail;
+
+		if (vsgt->num_pages > vmw_tt->sgt.nents) {
+			uint64_t over_alloc =
+				sgl_size * (vsgt->num_pages -
+					    vmw_tt->sgt.nents);
+
+			ttm_mem_global_free(glob, over_alloc);
+			vmw_tt->sg_alloc_size -= over_alloc;
+		}
+
+		ret = vmw_ttm_map_for_dma(vmw_tt);
+		if (unlikely(ret != 0))
+			goto out_map_fail;
+
+		break;
+	default:
+		break;
+	}
+
+	old = ~((dma_addr_t) 0);
+	vmw_tt->vsgt.num_regions = 0;
+	for (vmw_piter_start(&iter, vsgt, 0); vmw_piter_next(&iter);) {
+		dma_addr_t cur = vmw_piter_dma_addr(&iter);
+
+		if (cur != old + PAGE_SIZE)
+			vmw_tt->vsgt.num_regions++;
+		old = cur;
+	}
+
+	vmw_tt->mapped = true;
+	return 0;
+
+out_map_fail:
+	sg_free_table(vmw_tt->vsgt.sgt);
+	vmw_tt->vsgt.sgt = NULL;
+out_sg_alloc_fail:
+	ttm_mem_global_free(glob, vmw_tt->sg_alloc_size);
+	return ret;
+}
+
+/**
+ * vmw_ttm_unmap_dma - Tear down any TTM page device mappings
+ *
+ * @vmw_tt: Pointer to a struct vmw_ttm_tt
+ *
+ * Tear down any previously set up device DMA mappings and free
+ * any storage space allocated for them. If there are no mappings set up,
+ * this function is a NOP.
+ */
+static void vmw_ttm_unmap_dma(struct vmw_ttm_tt *vmw_tt)
+{
+	struct vmw_private *dev_priv = vmw_tt->dev_priv;
+
+	if (!vmw_tt->vsgt.sgt)
+		return;
+
+	switch (dev_priv->map_mode) {
+	case vmw_dma_map_bind:
+	case vmw_dma_map_populate:
+		vmw_ttm_unmap_from_dma(vmw_tt);
+		sg_free_table(vmw_tt->vsgt.sgt);
+		vmw_tt->vsgt.sgt = NULL;
+		ttm_mem_global_free(vmw_mem_glob(dev_priv),
+				    vmw_tt->sg_alloc_size);
+		break;
+	default:
+		break;
+	}
+	vmw_tt->mapped = false;
+}
+
 static int vmw_ttm_bind(struct ttm_tt *ttm, struct ttm_mem_reg *bo_mem)
 {
-	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
+	struct vmw_ttm_tt *vmw_be =
+		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
+	int ret;
+
+	ret = vmw_ttm_map_dma(vmw_be);
+	if (unlikely(ret != 0))
+		return ret;
 
 	vmw_be->gmr_id = bo_mem->start;
 
-	return vmw_gmr_bind(vmw_be->dev_priv, ttm->pages,
+	return vmw_gmr_bind(vmw_be->dev_priv, &vmw_be->vsgt,
 			    ttm->num_pages, vmw_be->gmr_id);
 }
 
 static int vmw_ttm_unbind(struct ttm_tt *ttm)
 {
-	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
+	struct vmw_ttm_tt *vmw_be =
+		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
 
 	vmw_gmr_unbind(vmw_be->dev_priv, vmw_be->gmr_id);
+
+	if (vmw_be->dev_priv->map_mode == vmw_dma_map_bind)
+		vmw_ttm_unmap_dma(vmw_be);
+
 	return 0;
 }
 
 static void vmw_ttm_destroy(struct ttm_tt *ttm)
 {
-	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
-
-	ttm_tt_fini(ttm);
+	struct vmw_ttm_tt *vmw_be =
+		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
+
+	vmw_ttm_unmap_dma(vmw_be);
+	if (vmw_be->dev_priv->map_mode == vmw_dma_alloc_coherent)
+		ttm_dma_tt_fini(&vmw_be->dma_ttm);
+	else
+		ttm_tt_fini(ttm);
 	kfree(vmw_be);
 }
 
+static int vmw_ttm_populate(struct ttm_tt *ttm)
+{
+	struct vmw_ttm_tt *vmw_tt =
+		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
+	struct vmw_private *dev_priv = vmw_tt->dev_priv;
+	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
+	int ret;
+
+	if (ttm->state != tt_unpopulated)
+		return 0;
+
+	if (dev_priv->map_mode == vmw_dma_alloc_coherent) {
+		size_t size =
+			ttm_round_pot(ttm->num_pages * sizeof(dma_addr_t));
+		ret = ttm_mem_global_alloc(glob, size, false, true);
+		if (unlikely(ret != 0))
+			return ret;
+
+		ret = ttm_dma_populate(&vmw_tt->dma_ttm, dev_priv->dev->dev);
+		if (unlikely(ret != 0))
+			ttm_mem_global_free(glob, size);
+	} else
+		ret = ttm_pool_populate(ttm);
+
+	return ret;
+}
+
+static void vmw_ttm_unpopulate(struct ttm_tt *ttm)
+{
+	struct vmw_ttm_tt *vmw_tt = container_of(ttm, struct vmw_ttm_tt,
+						 dma_ttm.ttm);
+	struct vmw_private *dev_priv = vmw_tt->dev_priv;
+	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
+
+	vmw_ttm_unmap_dma(vmw_tt);
+	if (dev_priv->map_mode == vmw_dma_alloc_coherent) {
+		size_t size =
+			ttm_round_pot(ttm->num_pages * sizeof(dma_addr_t));
+
+		ttm_dma_unpopulate(&vmw_tt->dma_ttm, dev_priv->dev->dev);
+		ttm_mem_global_free(glob, size);
+	} else
+		ttm_pool_unpopulate(ttm);
+}
+
 static struct ttm_backend_func vmw_ttm_func = {
 	.bind = vmw_ttm_bind,
 	.unbind = vmw_ttm_unbind,
@@ -183,20 +520,28 @@ struct ttm_tt *vmw_ttm_tt_create(struct ttm_bo_device *bdev,
 				 struct page *dummy_read_page)
 {
 	struct vmw_ttm_tt *vmw_be;
+	int ret;
 
-	vmw_be = kmalloc(sizeof(*vmw_be), GFP_KERNEL);
+	vmw_be = kzalloc(sizeof(*vmw_be), GFP_KERNEL);
 	if (!vmw_be)
 		return NULL;
 
-	vmw_be->ttm.func = &vmw_ttm_func;
+	vmw_be->dma_ttm.ttm.func = &vmw_ttm_func;
 	vmw_be->dev_priv = container_of(bdev, struct vmw_private, bdev);
 
-	if (ttm_tt_init(&vmw_be->ttm, bdev, size, page_flags, dummy_read_page)) {
-		kfree(vmw_be);
-		return NULL;
-	}
-
-	return &vmw_be->ttm;
+	if (vmw_be->dev_priv->map_mode == vmw_dma_alloc_coherent)
+		ret = ttm_dma_tt_init(&vmw_be->dma_ttm, bdev, size, page_flags,
+				      dummy_read_page);
+	else
+		ret = ttm_tt_init(&vmw_be->dma_ttm.ttm, bdev, size, page_flags,
+				  dummy_read_page);
+	if (unlikely(ret != 0))
+		goto out_no_init;
+
+	return &vmw_be->dma_ttm.ttm;
+out_no_init:
+	kfree(vmw_be);
+	return NULL;
 }
 
 int vmw_invalidate_caches(struct ttm_bo_device *bdev, uint32_t flags)
@@ -332,8 +677,8 @@ static int vmw_sync_obj_wait(void *sync_obj, bool lazy, bool interruptible)
 
 struct ttm_bo_driver vmw_bo_driver = {
 	.ttm_tt_create = &vmw_ttm_tt_create,
-	.ttm_tt_populate = &ttm_pool_populate,
-	.ttm_tt_unpopulate = &ttm_pool_unpopulate,
+	.ttm_tt_populate = &vmw_ttm_populate,
+	.ttm_tt_unpopulate = &vmw_ttm_unpopulate,
 	.invalidate_caches = vmw_invalidate_caches,
 	.init_mem_type = vmw_init_mem_type,
 	.evict_flags = vmw_evict_flags,
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 1a90f0a..0b5c781 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -32,6 +32,7 @@
 #include <drm/ttm/ttm_bo_driver.h>
 #include <drm/ttm/ttm_object.h>
 #include <drm/ttm/ttm_module.h>
+#include <linux/dma_remapping.h>
 
 #define VMWGFX_DRIVER_NAME "vmwgfx"
 #define VMWGFX_DRIVER_DESC "Linux drm driver for VMware graphics devices"
@@ -185,6 +186,9 @@ static struct pci_device_id vmw_pci_id_list[] = {
 MODULE_DEVICE_TABLE(pci, vmw_pci_id_list);
 
 static int enable_fbdev = IS_ENABLED(CONFIG_DRM_VMWGFX_FBCON);
+static int vmw_force_iommu;
+static int vmw_restrict_iommu;
+static int vmw_force_coherent;
 
 static int vmw_probe(struct pci_dev *, const struct pci_device_id *);
 static void vmw_master_init(struct vmw_master *);
@@ -193,6 +197,13 @@ static int vmwgfx_pm_notifier(struct notifier_block *nb, unsigned long val,
 
 MODULE_PARM_DESC(enable_fbdev, "Enable vmwgfx fbdev");
 module_param_named(enable_fbdev, enable_fbdev, int, 0600);
+MODULE_PARM_DESC(force_dma_api, "Force using the DMA API for TTM pages");
+module_param_named(force_dma_api, vmw_force_iommu, int, 0600);
+MODULE_PARM_DESC(restrict_iommu, "Try to limit IOMMU usage for TTM pages");
+module_param_named(restrict_iommu, vmw_restrict_iommu, int, 0600);
+MODULE_PARM_DESC(force_coherent, "Force coherent TTM pages");
+module_param_named(force_coherent, vmw_force_coherent, int, 0600);
+
 
 static void vmw_print_capabilities(uint32_t capabilities)
 {
@@ -427,12 +438,78 @@ static void vmw_get_initial_size(struct vmw_private *dev_priv)
 	dev_priv->initial_height = height;
 }
 
+/**
+ * vmw_dma_select_mode - Determine how DMA mappings should be set up for this
+ * system.
+ *
+ * @dev_priv: Pointer to a struct vmw_private
+ *
+ * This functions tries to determine the IOMMU setup and what actions
+ * need to be taken by the driver to make system pages visible to the
+ * device.
+ * If this function decides that DMA is not possible, it returns -EINVAL.
+ * The driver may then try to disable features of the device that require
+ * DMA.
+ */
+static int vmw_dma_select_mode(struct vmw_private *dev_priv)
+{
+	const struct dma_map_ops *dma_ops = get_dma_ops(dev_priv->dev->dev);
+	static const char *names[vmw_dma_map_max] = {
+		[vmw_dma_phys] = "Using physical TTM page addresses.",
+		[vmw_dma_alloc_coherent] = "Using coherent TTM pages.",
+		[vmw_dma_map_populate] = "Keeping DMA mappings.",
+		[vmw_dma_map_bind] = "Giving up DMA mappings early."};
+
+#ifdef CONFIG_INTEL_IOMMU
+	if (intel_iommu_enabled) {
+		dev_priv->map_mode = vmw_dma_map_populate;
+		goto out_fixup;
+	}
+#endif
+
+	if (!(vmw_force_iommu || vmw_force_coherent)) {
+		dev_priv->map_mode = vmw_dma_phys;
+		DRM_INFO("DMA map mode: %s\n", names[dev_priv->map_mode]);
+		return 0;
+	}
+
+	dev_priv->map_mode = vmw_dma_map_populate;
+
+	if (dma_ops->sync_single_for_cpu)
+		dev_priv->map_mode = vmw_dma_alloc_coherent;
+#ifdef CONFIG_SWIOTLB
+	if (swiotlb_nr_tbl() == 0)
+		dev_priv->map_mode = vmw_dma_map_populate;
+#endif
+
+out_fixup:
+	if (dev_priv->map_mode == vmw_dma_map_populate &&
+	    vmw_restrict_iommu)
+		dev_priv->map_mode = vmw_dma_map_bind;
+
+	if (vmw_force_coherent)
+		dev_priv->map_mode = vmw_dma_alloc_coherent;
+
+#if !defined(CONFIG_SWIOTLB) && !defined(CONFIG_INTEL_IOMMU)
+	/*
+	 * No coherent page pool
+	 */
+	if (dev_priv->map_mode == vmw_dma_alloc_coherent)
+		return -EINVAL;
+#endif
+
+	DRM_INFO("DMA map mode: %s\n", names[dev_priv->map_mode]);
+
+	return 0;
+}
+
 static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 {
 	struct vmw_private *dev_priv;
 	int ret;
 	uint32_t svga_id;
 	enum vmw_res_type i;
+	bool refuse_dma = false;
 
 	dev_priv = kzalloc(sizeof(*dev_priv), GFP_KERNEL);
 	if (unlikely(dev_priv == NULL)) {
@@ -481,6 +558,11 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 	}
 
 	dev_priv->capabilities = vmw_read(dev_priv, SVGA_REG_CAPABILITIES);
+	ret = vmw_dma_select_mode(dev_priv);
+	if (unlikely(ret != 0)) {
+		DRM_INFO("Restricting capabilities due to IOMMU setup.\n");
+		refuse_dma = true;
+	}
 
 	dev_priv->vram_size = vmw_read(dev_priv, SVGA_REG_VRAM_SIZE);
 	dev_priv->mmio_size = vmw_read(dev_priv, SVGA_REG_MEM_SIZE);
@@ -558,8 +640,9 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 	}
 
 	dev_priv->has_gmr = true;
-	if (ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_GMR,
-			   dev_priv->max_gmr_ids) != 0) {
+	if (((dev_priv->capabilities & (SVGA_CAP_GMR | SVGA_CAP_GMR2)) == 0) ||
+	    refuse_dma || ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_GMR,
+					 dev_priv->max_gmr_ids) != 0) {
 		DRM_INFO("No GMR memory available. "
 			 "Graphics memory resources are very limited.\n");
 		dev_priv->has_gmr = false;
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index 150ec64..e401d5d 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -177,6 +177,58 @@ struct vmw_res_cache_entry {
 	struct vmw_resource_val_node *node;
 };
 
+/**
+ * enum vmw_dma_map_mode - indicate how to perform TTM page dma mappings.
+ */
+enum vmw_dma_map_mode {
+	vmw_dma_phys,           /* Use physical page addresses */
+	vmw_dma_alloc_coherent, /* Use TTM coherent pages */
+	vmw_dma_map_populate,   /* Unmap from DMA just after unpopulate */
+	vmw_dma_map_bind,       /* Unmap from DMA just before unbind */
+	vmw_dma_map_max
+};
+
+/**
+ * struct vmw_sg_table - Scatter/gather table for binding, with additional
+ * device-specific information.
+ *
+ * @sgt: Pointer to a struct sg_table with binding information
+ * @num_regions: Number of regions with device-address contigous pages
+ */
+struct vmw_sg_table {
+	enum vmw_dma_map_mode mode;
+	struct page **pages;
+	const dma_addr_t *addrs;
+	struct sg_table *sgt;
+	unsigned long num_regions;
+	unsigned long num_pages;
+};
+
+/**
+ * struct vmw_piter - Page iterator that iterates over a list of pages
+ * and DMA addresses that could be either a scatter-gather list or
+ * arrays
+ *
+ * @pages: Array of page pointers to the pages.
+ * @addrs: DMA addresses to the pages if coherent pages are used.
+ * @iter: Scatter-gather page iterator. Current position in SG list.
+ * @i: Current position in arrays.
+ * @num_pages: Number of pages total.
+ * @next: Function to advance the iterator. Returns false if past the list
+ * of pages, true otherwise.
+ * @dma_address: Function to return the DMA address of the current page.
+ */
+struct vmw_piter {
+	struct page **pages;
+	const dma_addr_t *addrs;
+	struct sg_page_iter iter;
+	unsigned long i;
+	unsigned long num_pages;
+	bool (*next)(struct vmw_piter *);
+	dma_addr_t (*dma_address)(struct vmw_piter *);
+	struct page *(*page)(struct vmw_piter *);
+};
+
 struct vmw_sw_context{
 	struct drm_open_hash res_ht;
 	bool res_ht_initialized;
@@ -358,6 +410,11 @@ struct vmw_private {
 
 	struct list_head res_lru[vmw_res_max];
 	uint32_t used_memory_size;
+
+	/*
+	 * DMA mapping stuff.
+	 */
+	enum vmw_dma_map_mode map_mode;
 };
 
 static inline struct vmw_surface *vmw_res_to_srf(struct vmw_resource *res)
@@ -405,7 +462,7 @@ void vmw_3d_resource_dec(struct vmw_private *dev_priv, bool hide_svga);
  */
 
 extern int vmw_gmr_bind(struct vmw_private *dev_priv,
-			struct page *pages[],
+			const struct vmw_sg_table *vsgt,
 			unsigned long num_pages,
 			int gmr_id);
 extern void vmw_gmr_unbind(struct vmw_private *dev_priv, int gmr_id);
@@ -568,6 +625,45 @@ extern struct ttm_placement vmw_evictable_placement;
 extern struct ttm_placement vmw_srf_placement;
 extern struct ttm_bo_driver vmw_bo_driver;
 extern int vmw_dma_quiescent(struct drm_device *dev);
+extern void vmw_piter_start(struct vmw_piter *viter,
+			    const struct vmw_sg_table *vsgt,
+			    unsigned long p_offs);
+
+/**
+ * vmw_piter_next - Advance the iterator one page.
+ *
+ * @viter: Pointer to the iterator to advance.
+ *
+ * Returns false if past the list of pages, true otherwise.
+ */
+static inline bool vmw_piter_next(struct vmw_piter *viter)
+{
+	return viter->next(viter);
+}
+
+/**
+ * vmw_piter_dma_addr - Return the DMA address of the current page.
+ *
+ * @viter: Pointer to the iterator
+ *
+ * Returns the DMA address of the page pointed to by @viter.
+ */
+static inline dma_addr_t vmw_piter_dma_addr(struct vmw_piter *viter)
+{
+	return viter->dma_address(viter);
+}
+
+/**
+ * vmw_piter_page - Return a pointer to the current page.
+ *
+ * @viter: Pointer to the iterator
+ *
+ * Returns the DMA address of the page pointed to by @viter.
+ */
+static inline struct page *vmw_piter_page(struct vmw_piter *viter)
+{
+	return viter->page(viter);
+}
 
 /**
  * Command submission - vmwgfx_execbuf.c
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c b/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
index 1a0bf07..6d09523 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
@@ -32,9 +32,11 @@
 #define VMW_PPN_SIZE (sizeof(unsigned long))
 /* A future safe maximum remap size. */
 #define VMW_PPN_PER_REMAP ((31 * 1024) / VMW_PPN_SIZE)
+#define DMA_ADDR_INVALID ((dma_addr_t) 0)
+#define DMA_PAGE_INVALID 0UL
 
 static int vmw_gmr2_bind(struct vmw_private *dev_priv,
-			 struct page *pages[],
+			 struct vmw_piter *iter,
 			 unsigned long num_pages,
 			 int gmr_id)
 {
@@ -81,11 +83,13 @@ static int vmw_gmr2_bind(struct vmw_private *dev_priv,
 
 		for (i = 0; i < nr; ++i) {
 			if (VMW_PPN_SIZE <= 4)
-				*cmd = page_to_pfn(*pages++);
+				*cmd = vmw_piter_dma_addr(iter) >> PAGE_SHIFT;
 			else
-				*((uint64_t *)cmd) = page_to_pfn(*pages++);
+				*((uint64_t *)cmd) = vmw_piter_dma_addr(iter) >>
+					PAGE_SHIFT;
 
 			cmd += VMW_PPN_SIZE / sizeof(*cmd);
+			vmw_piter_next(iter);
 		}
 
 		num_pages -= nr;
@@ -120,22 +124,54 @@ static void vmw_gmr2_unbind(struct vmw_private *dev_priv,
 	vmw_fifo_commit(dev_priv, define_size);
 }
 
+
+static void vmw_gmr_free_descriptors(struct device *dev, dma_addr_t desc_dma,
+				     struct list_head *desc_pages)
+{
+	struct page *page, *next;
+	struct svga_guest_mem_descriptor *page_virtual;
+	unsigned int desc_per_page = PAGE_SIZE /
+		sizeof(struct svga_guest_mem_descriptor) - 1;
+
+	if (list_empty(desc_pages))
+		return;
+
+	list_for_each_entry_safe(page, next, desc_pages, lru) {
+		list_del_init(&page->lru);
+
+		if (likely(desc_dma != DMA_ADDR_INVALID)) {
+			dma_unmap_page(dev, desc_dma, PAGE_SIZE,
+				       DMA_TO_DEVICE);
+		}
+
+		page_virtual = kmap_atomic(page);
+		desc_dma = page_virtual[desc_per_page].ppn << PAGE_SHIFT;
+		kunmap_atomic(page_virtual);
+
+		__free_page(page);
+	}
+}
+
 /**
  * FIXME: Adjust to the ttm lowmem / highmem storage to minimize
  * the number of used descriptors.
+ *
  */
 
-static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
-				     struct page *pages[],
-				     unsigned long num_pages)
+static int vmw_gmr_build_descriptors(struct device *dev,
+				     struct list_head *desc_pages,
+				     struct vmw_piter *iter,
+				     unsigned long num_pages,
+				     dma_addr_t *first_dma)
 {
-	struct page *page, *next;
+	struct page *page;
 	struct svga_guest_mem_descriptor *page_virtual = NULL;
 	struct svga_guest_mem_descriptor *desc_virtual = NULL;
 	unsigned int desc_per_page;
 	unsigned long prev_pfn;
 	unsigned long pfn;
 	int ret;
+	dma_addr_t desc_dma;
 
 	desc_per_page = PAGE_SIZE /
 	    sizeof(struct svga_guest_mem_descriptor) - 1;
@@ -148,23 +184,12 @@ static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
 		}
 
 		list_add_tail(&page->lru, desc_pages);
-
-		/*
-		 * Point previous page terminating descriptor to this
-		 * page before unmapping it.
-		 */
-
-		if (likely(page_virtual != NULL)) {
-			desc_virtual->ppn = page_to_pfn(page);
-			kunmap_atomic(page_virtual);
-		}
-
 		page_virtual = kmap_atomic(page);
 		desc_virtual = page_virtual - 1;
 		prev_pfn = ~(0UL);
 
 		while (likely(num_pages != 0)) {
-			pfn = page_to_pfn(*pages);
+			pfn = vmw_piter_dma_addr(iter) >> PAGE_SHIFT;
 
 			if (pfn != prev_pfn + 1) {
 
@@ -181,104 +206,81 @@ static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
 			}
 			prev_pfn = pfn;
 			--num_pages;
-			++pages;
+			vmw_piter_next(iter);
 		}
 
-		(++desc_virtual)->ppn = cpu_to_le32(0);
+		(++desc_virtual)->ppn = DMA_PAGE_INVALID;
 		desc_virtual->num_pages = cpu_to_le32(0);
+		kunmap_atomic(page_virtual);
 	}
 
-	if (likely(page_virtual != NULL))
+	desc_dma = 0;
+	list_for_each_entry_reverse(page, desc_pages, lru) {
+		page_virtual = kmap_atomic(page);
+		page_virtual[desc_per_page].ppn = desc_dma >> PAGE_SHIFT;
 		kunmap_atomic(page_virtual);
+		desc_dma = dma_map_page(dev, page, 0, PAGE_SIZE,
+					DMA_TO_DEVICE);
+
+		if (unlikely(dma_mapping_error(dev, desc_dma)))
+			goto out_err;
+	}
+	*first_dma = desc_dma;
 
 	return 0;
 out_err:
-	list_for_each_entry_safe(page, next, desc_pages, lru) {
-		list_del_init(&page->lru);
-		__free_page(page);
-	}
+	vmw_gmr_free_descriptors(dev, DMA_ADDR_INVALID, desc_pages);
 	return ret;
 }
 
-static inline void vmw_gmr_free_descriptors(struct list_head *desc_pages)
-{
-	struct page *page, *next;
-
-	list_for_each_entry_safe(page, next, desc_pages, lru) {
-		list_del_init(&page->lru);
-		__free_page(page);
-	}
-}
-
 static void vmw_gmr_fire_descriptors(struct vmw_private *dev_priv,
-				     int gmr_id, struct list_head *desc_pages)
+				     int gmr_id, dma_addr_t desc_dma)
 {
-	struct page *page;
-
-	if (unlikely(list_empty(desc_pages)))
-		return;
-
-	page = list_entry(desc_pages->next, struct page, lru);
-
 	mutex_lock(&dev_priv->hw_mutex);
 
 	vmw_write(dev_priv, SVGA_REG_GMR_ID, gmr_id);
 	wmb();
-	vmw_write(dev_priv, SVGA_REG_GMR_DESCRIPTOR, page_to_pfn(page));
+	vmw_write(dev_priv, SVGA_REG_GMR_DESCRIPTOR, desc_dma >> PAGE_SHIFT);
 	mb();
 
 	mutex_unlock(&dev_priv->hw_mutex);
 
 }
 
-/**
- * FIXME: Adjust to the ttm lowmem / highmem storage to minimize
- * the number of used descriptors.
- */
-
-static unsigned long vmw_gmr_count_descriptors(struct page *pages[],
-					unsigned long num_pages)
-{
-	unsigned long prev_pfn = ~(0UL);
-	unsigned long pfn;
-	unsigned long descriptors = 0;
-
-	while (num_pages--) {
-		pfn = page_to_pfn(*pages++);
-		if (prev_pfn + 1 != pfn)
-			++descriptors;
-		prev_pfn = pfn;
-	}
-
-	return descriptors;
-}
-
 int vmw_gmr_bind(struct vmw_private *dev_priv,
-		 struct page *pages[],
+		 const struct vmw_sg_table *vsgt,
 		 unsigned long num_pages,
 		 int gmr_id)
 {
 	struct list_head desc_pages;
+	dma_addr_t desc_dma = 0;
+	struct device *dev = dev_priv->dev->dev;
+	struct vmw_piter data_iter;
 	int ret;
 
+	vmw_piter_start(&data_iter, vsgt, 0);
+
+	if (unlikely(!vmw_piter_next(&data_iter)))
+		return 0;
+
 	if (likely(dev_priv->capabilities & SVGA_CAP_GMR2))
-		return vmw_gmr2_bind(dev_priv, pages, num_pages, gmr_id);
+		return vmw_gmr2_bind(dev_priv, &data_iter, num_pages, gmr_id);
 
 	if (unlikely(!(dev_priv->capabilities & SVGA_CAP_GMR)))
 		return -EINVAL;
 
-	if (vmw_gmr_count_descriptors(pages, num_pages) >
-	    dev_priv->max_gmr_descriptors)
+	if (vsgt->num_regions > dev_priv->max_gmr_descriptors)
 		return -EINVAL;
 
 	INIT_LIST_HEAD(&desc_pages);
 
-	ret = vmw_gmr_build_descriptors(&desc_pages, pages, num_pages);
+	ret = vmw_gmr_build_descriptors(dev, &desc_pages, &data_iter,
+					num_pages, &desc_dma);
 	if (unlikely(ret != 0))
 		return ret;
 
-	vmw_gmr_fire_descriptors(dev_priv, gmr_id, &desc_pages);
-	vmw_gmr_free_descriptors(&desc_pages);
+	vmw_gmr_fire_descriptors(dev_priv, gmr_id, desc_dma);
+	vmw_gmr_free_descriptors(dev, desc_dma, &desc_pages);
 
 	return 0;
 }
-- 
1.7.10.4

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--

Re: [PATCH 2/2] drm/vmwgfx: Use the linux DMA api to get valid device addresses of pages

[Daniel Vetter]

On Mon, Nov 04, 2013 at 05:57:39AM -0800, Thomas Hellstrom wrote:
> The code handles three different cases:
> 1) physical page addresses. The ttm page array is used.
> 2) DMA subsystem addresses. A scatter-gather list is used.
> 3) Coherent pages. The ttm dma pool is used, together with the dma_ttm
> array os dma_addr_t
> 
> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

For i915.ko use we've added page iterators which should walk the physical
backing storage.

commit a321e91b6d73ed011ffceed384c40d2785cf723b
Author: Imre Deak <imre.deak@intel.com>
Date:   Wed Feb 27 17:02:56 2013 -0800

    lib/scatterlist: add simple page iterator

Now we've unified all our backing storage handling around sg tables (even
for stolen memory), so maybe that's not useful for you guys. Just figured
I'll drop this here, it imo made our code look fairly tidy.

Cheers, Daniel

> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c |  379 ++++++++++++++++++++++++++++++--
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    |   87 +++++++-
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h    |   98 ++++++++-
>  drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c    |  150 ++++++-------
>  4 files changed, 620 insertions(+), 94 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
> index 96dc84d..7776e6f 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
> @@ -141,37 +141,374 @@ struct ttm_placement vmw_srf_placement = {
>  };
>  
>  struct vmw_ttm_tt {
> -	struct ttm_tt ttm;
> +	struct ttm_dma_tt dma_ttm;
>  	struct vmw_private *dev_priv;
>  	int gmr_id;
> +	struct sg_table sgt;
> +	struct vmw_sg_table vsgt;
> +	uint64_t sg_alloc_size;
> +	bool mapped;
>  };
>  
> +/**
> + * Helper functions to advance a struct vmw_piter iterator.
> + *
> + * @viter: Pointer to the iterator.
> + *
> + * These functions return false if past the end of the list,
> + * true otherwise. Functions are selected depending on the current
> + * DMA mapping mode.
> + */
> +static bool __vmw_piter_non_sg_next(struct vmw_piter *viter)
> +{
> +	return ++(viter->i) < viter->num_pages;
> +}
> +
> +static bool __vmw_piter_sg_next(struct vmw_piter *viter)
> +{
> +	return __sg_page_iter_next(&viter->iter);
> +}
> +
> +
> +/**
> + * Helper functions to return a pointer to the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * These functions return a pointer to the page currently
> + * pointed to by @viter. Functions are selected depending on the
> + * current mapping mode.
> + */
> +static struct page *__vmw_piter_non_sg_page(struct vmw_piter *viter)
> +{
> +	return viter->pages[viter->i];
> +}
> +
> +static struct page *__vmw_piter_sg_page(struct vmw_piter *viter)
> +{
> +	return sg_page_iter_page(&viter->iter);
> +}
> +
> +
> +/**
> + * Helper functions to return the DMA address of the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * These functions return the DMA address of the page currently
> + * pointed to by @viter. Functions are selected depending on the
> + * current mapping mode.
> + */
> +static dma_addr_t __vmw_piter_phys_addr(struct vmw_piter *viter)
> +{
> +	return page_to_phys(viter->pages[viter->i]);
> +}
> +
> +static dma_addr_t __vmw_piter_dma_addr(struct vmw_piter *viter)
> +{
> +	return viter->addrs[viter->i];
> +}
> +
> +static dma_addr_t __vmw_piter_sg_addr(struct vmw_piter *viter)
> +{
> +	return sg_page_iter_dma_address(&viter->iter);
> +}
> +
> +
> +/**
> + * vmw_piter_start - Initialize a struct vmw_piter.
> + *
> + * @viter: Pointer to the iterator to initialize
> + * @vsgt: Pointer to a struct vmw_sg_table to initialize from
> + *
> + * Note that we're following the convention of __sg_page_iter_start, so that
> + * the iterator doesn't point to a valid page after initialization; it has
> + * to be advanced one step first.
> + */
> +void vmw_piter_start(struct vmw_piter *viter, const struct vmw_sg_table *vsgt,
> +		     unsigned long p_offset)
> +{
> +	viter->i = p_offset - 1;
> +	viter->num_pages = vsgt->num_pages;
> +	switch (vsgt->mode) {
> +	case vmw_dma_phys:
> +		viter->next = &__vmw_piter_non_sg_next;
> +		viter->dma_address = &__vmw_piter_phys_addr;
> +		viter->page = &__vmw_piter_non_sg_page;
> +		viter->pages = vsgt->pages;
> +		break;
> +	case vmw_dma_alloc_coherent:
> +		viter->next = &__vmw_piter_non_sg_next;
> +		viter->dma_address = &__vmw_piter_dma_addr;
> +		viter->page = &__vmw_piter_non_sg_page;
> +		viter->addrs = vsgt->addrs;
> +		break;
> +	case vmw_dma_map_populate:
> +	case vmw_dma_map_bind:
> +		viter->next = &__vmw_piter_sg_next;
> +		viter->dma_address = &__vmw_piter_sg_addr;
> +		viter->page = &__vmw_piter_sg_page;
> +		__sg_page_iter_start(&viter->iter, vsgt->sgt->sgl,
> +				     vsgt->sgt->orig_nents, p_offset);
> +		break;
> +	default:
> +		BUG();
> +	}
> +}
> +
> +/**
> + * vmw_ttm_unmap_from_dma - unmap  device addresses previsouly mapped for
> + * TTM pages
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_backend
> + *
> + * Used to free dma mappings previously mapped by vmw_ttm_map_for_dma.
> + */
> +static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct device *dev = vmw_tt->dev_priv->dev->dev;
> +
> +	dma_unmap_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.nents,
> +		DMA_BIDIRECTIONAL);
> +	vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents;
> +}
> +
> +/**
> + * vmw_ttm_map_for_dma - map TTM pages to get device addresses
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_backend
> + *
> + * This function is used to get device addresses from the kernel DMA layer.
> + * However, it's violating the DMA API in that when this operation has been
> + * performed, it's illegal for the CPU to write to the pages without first
> + * unmapping the DMA mappings, or calling dma_sync_sg_for_cpu(). It is
> + * therefore only legal to call this function if we know that the function
> + * dma_sync_sg_for_cpu() is a NOP, and dma_sync_sg_for_device() is at most
> + * a CPU write buffer flush.
> + */
> +static int vmw_ttm_map_for_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct device *dev = vmw_tt->dev_priv->dev->dev;
> +	int ret;
> +
> +	ret = dma_map_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.orig_nents,
> +			 DMA_BIDIRECTIONAL);
> +	if (unlikely(ret == 0))
> +		return -ENOMEM;
> +
> +	vmw_tt->sgt.nents = ret;
> +
> +	return 0;
> +}
> +
> +/**
> + * vmw_ttm_map_dma - Make sure TTM pages are visible to the device
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_tt
> + *
> + * Select the correct function for and make sure the TTM pages are
> + * visible to the device. Allocate storage for the device mappings.
> + * If a mapping has already been performed, indicated by the storage
> + * pointer being non NULL, the function returns success.
> + */
> +static int vmw_ttm_map_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
> +	struct vmw_sg_table *vsgt = &vmw_tt->vsgt;
> +	struct vmw_piter iter;
> +	dma_addr_t old;
> +	int ret = 0;
> +	static size_t sgl_size;
> +	static size_t sgt_size;
> +
> +	if (vmw_tt->mapped)
> +		return 0;
> +
> +	vsgt->mode = dev_priv->map_mode;
> +	vsgt->pages = vmw_tt->dma_ttm.ttm.pages;
> +	vsgt->num_pages = vmw_tt->dma_ttm.ttm.num_pages;
> +	vsgt->addrs = vmw_tt->dma_ttm.dma_address;
> +	vsgt->sgt = &vmw_tt->sgt;
> +
> +	switch (dev_priv->map_mode) {
> +	case vmw_dma_map_bind:
> +	case vmw_dma_map_populate:
> +		if (unlikely(!sgl_size)) {
> +			sgl_size = ttm_round_pot(sizeof(struct scatterlist));
> +			sgt_size = ttm_round_pot(sizeof(struct sg_table));
> +		}
> +		vmw_tt->sg_alloc_size = sgt_size + sgl_size * vsgt->num_pages;
> +		ret = ttm_mem_global_alloc(glob, vmw_tt->sg_alloc_size, false,
> +					   true);
> +		if (unlikely(ret != 0))
> +			return ret;
> +
> +		ret = sg_alloc_table_from_pages(&vmw_tt->sgt, vsgt->pages,
> +						vsgt->num_pages, 0,
> +						(unsigned long)
> +						vsgt->num_pages << PAGE_SHIFT,
> +						GFP_KERNEL);
> +		if (unlikely(ret != 0))
> +			goto out_sg_alloc_fail;
> +
> +		if (vsgt->num_pages > vmw_tt->sgt.nents) {
> +			uint64_t over_alloc =
> +				sgl_size * (vsgt->num_pages -
> +					    vmw_tt->sgt.nents);
> +
> +			ttm_mem_global_free(glob, over_alloc);
> +			vmw_tt->sg_alloc_size -= over_alloc;
> +		}
> +
> +		ret = vmw_ttm_map_for_dma(vmw_tt);
> +		if (unlikely(ret != 0))
> +			goto out_map_fail;
> +
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	old = ~((dma_addr_t) 0);
> +	vmw_tt->vsgt.num_regions = 0;
> +	for (vmw_piter_start(&iter, vsgt, 0); vmw_piter_next(&iter);) {
> +		dma_addr_t cur = vmw_piter_dma_addr(&iter);
> +
> +		if (cur != old + PAGE_SIZE)
> +			vmw_tt->vsgt.num_regions++;
> +		old = cur;
> +	}
> +
> +	vmw_tt->mapped = true;
> +	return 0;
> +
> +out_map_fail:
> +	sg_free_table(vmw_tt->vsgt.sgt);
> +	vmw_tt->vsgt.sgt = NULL;
> +out_sg_alloc_fail:
> +	ttm_mem_global_free(glob, vmw_tt->sg_alloc_size);
> +	return ret;
> +}
> +
> +/**
> + * vmw_ttm_unmap_dma - Tear down any TTM page device mappings
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_tt
> + *
> + * Tear down any previously set up device DMA mappings and free
> + * any storage space allocated for them. If there are no mappings set up,
> + * this function is a NOP.
> + */
> +static void vmw_ttm_unmap_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +
> +	if (!vmw_tt->vsgt.sgt)
> +		return;
> +
> +	switch (dev_priv->map_mode) {
> +	case vmw_dma_map_bind:
> +	case vmw_dma_map_populate:
> +		vmw_ttm_unmap_from_dma(vmw_tt);
> +		sg_free_table(vmw_tt->vsgt.sgt);
> +		vmw_tt->vsgt.sgt = NULL;
> +		ttm_mem_global_free(vmw_mem_glob(dev_priv),
> +				    vmw_tt->sg_alloc_size);
> +		break;
> +	default:
> +		break;
> +	}
> +	vmw_tt->mapped = false;
> +}
> +
>  static int vmw_ttm_bind(struct ttm_tt *ttm, struct ttm_mem_reg *bo_mem)
>  {
> -	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
> +	struct vmw_ttm_tt *vmw_be =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
> +	int ret;
> +
> +	ret = vmw_ttm_map_dma(vmw_be);
> +	if (unlikely(ret != 0))
> +		return ret;
>  
>  	vmw_be->gmr_id = bo_mem->start;
>  
> -	return vmw_gmr_bind(vmw_be->dev_priv, ttm->pages,
> +	return vmw_gmr_bind(vmw_be->dev_priv, &vmw_be->vsgt,
>  			    ttm->num_pages, vmw_be->gmr_id);
>  }
>  
>  static int vmw_ttm_unbind(struct ttm_tt *ttm)
>  {
> -	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
> +	struct vmw_ttm_tt *vmw_be =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
>  
>  	vmw_gmr_unbind(vmw_be->dev_priv, vmw_be->gmr_id);
> +
> +	if (vmw_be->dev_priv->map_mode == vmw_dma_map_bind)
> +		vmw_ttm_unmap_dma(vmw_be);
> +
>  	return 0;
>  }
>  
>  static void vmw_ttm_destroy(struct ttm_tt *ttm)
>  {
> -	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
> -
> -	ttm_tt_fini(ttm);
> +	struct vmw_ttm_tt *vmw_be =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
> +
> +	vmw_ttm_unmap_dma(vmw_be);
> +	if (vmw_be->dev_priv->map_mode == vmw_dma_alloc_coherent)
> +		ttm_dma_tt_fini(&vmw_be->dma_ttm);
> +	else
> +		ttm_tt_fini(ttm);
>  	kfree(vmw_be);
>  }
>  
> +static int vmw_ttm_populate(struct ttm_tt *ttm)
> +{
> +	struct vmw_ttm_tt *vmw_tt =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
> +	int ret;
> +
> +	if (ttm->state != tt_unpopulated)
> +		return 0;
> +
> +	if (dev_priv->map_mode == vmw_dma_alloc_coherent) {
> +		size_t size =
> +			ttm_round_pot(ttm->num_pages * sizeof(dma_addr_t));
> +		ret = ttm_mem_global_alloc(glob, size, false, true);
> +		if (unlikely(ret != 0))
> +			return ret;
> +
> +		ret = ttm_dma_populate(&vmw_tt->dma_ttm, dev_priv->dev->dev);
> +		if (unlikely(ret != 0))
> +			ttm_mem_global_free(glob, size);
> +	} else
> +		ret = ttm_pool_populate(ttm);
> +
> +	return ret;
> +}
> +
> +static void vmw_ttm_unpopulate(struct ttm_tt *ttm)
> +{
> +	struct vmw_ttm_tt *vmw_tt = container_of(ttm, struct vmw_ttm_tt,
> +						 dma_ttm.ttm);
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
> +
> +	vmw_ttm_unmap_dma(vmw_tt);
> +	if (dev_priv->map_mode == vmw_dma_alloc_coherent) {
> +		size_t size =
> +			ttm_round_pot(ttm->num_pages * sizeof(dma_addr_t));
> +
> +		ttm_dma_unpopulate(&vmw_tt->dma_ttm, dev_priv->dev->dev);
> +		ttm_mem_global_free(glob, size);
> +	} else
> +		ttm_pool_unpopulate(ttm);
> +}
> +
>  static struct ttm_backend_func vmw_ttm_func = {
>  	.bind = vmw_ttm_bind,
>  	.unbind = vmw_ttm_unbind,
> @@ -183,20 +520,28 @@ struct ttm_tt *vmw_ttm_tt_create(struct ttm_bo_device *bdev,
>  				 struct page *dummy_read_page)
>  {
>  	struct vmw_ttm_tt *vmw_be;
> +	int ret;
>  
> -	vmw_be = kmalloc(sizeof(*vmw_be), GFP_KERNEL);
> +	vmw_be = kzalloc(sizeof(*vmw_be), GFP_KERNEL);
>  	if (!vmw_be)
>  		return NULL;
>  
> -	vmw_be->ttm.func = &vmw_ttm_func;
> +	vmw_be->dma_ttm.ttm.func = &vmw_ttm_func;
>  	vmw_be->dev_priv = container_of(bdev, struct vmw_private, bdev);
>  
> -	if (ttm_tt_init(&vmw_be->ttm, bdev, size, page_flags, dummy_read_page)) {
> -		kfree(vmw_be);
> -		return NULL;
> -	}
> -
> -	return &vmw_be->ttm;
> +	if (vmw_be->dev_priv->map_mode == vmw_dma_alloc_coherent)
> +		ret = ttm_dma_tt_init(&vmw_be->dma_ttm, bdev, size, page_flags,
> +				      dummy_read_page);
> +	else
> +		ret = ttm_tt_init(&vmw_be->dma_ttm.ttm, bdev, size, page_flags,
> +				  dummy_read_page);
> +	if (unlikely(ret != 0))
> +		goto out_no_init;
> +
> +	return &vmw_be->dma_ttm.ttm;
> +out_no_init:
> +	kfree(vmw_be);
> +	return NULL;
>  }
>  
>  int vmw_invalidate_caches(struct ttm_bo_device *bdev, uint32_t flags)
> @@ -332,8 +677,8 @@ static int vmw_sync_obj_wait(void *sync_obj, bool lazy, bool interruptible)
>  
>  struct ttm_bo_driver vmw_bo_driver = {
>  	.ttm_tt_create = &vmw_ttm_tt_create,
> -	.ttm_tt_populate = &ttm_pool_populate,
> -	.ttm_tt_unpopulate = &ttm_pool_unpopulate,
> +	.ttm_tt_populate = &vmw_ttm_populate,
> +	.ttm_tt_unpopulate = &vmw_ttm_unpopulate,
>  	.invalidate_caches = vmw_invalidate_caches,
>  	.init_mem_type = vmw_init_mem_type,
>  	.evict_flags = vmw_evict_flags,
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 1a90f0a..0b5c781 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -32,6 +32,7 @@
>  #include <drm/ttm/ttm_bo_driver.h>
>  #include <drm/ttm/ttm_object.h>
>  #include <drm/ttm/ttm_module.h>
> +#include <linux/dma_remapping.h>
>  
>  #define VMWGFX_DRIVER_NAME "vmwgfx"
>  #define VMWGFX_DRIVER_DESC "Linux drm driver for VMware graphics devices"
> @@ -185,6 +186,9 @@ static struct pci_device_id vmw_pci_id_list[] = {
>  MODULE_DEVICE_TABLE(pci, vmw_pci_id_list);
>  
>  static int enable_fbdev = IS_ENABLED(CONFIG_DRM_VMWGFX_FBCON);
> +static int vmw_force_iommu;
> +static int vmw_restrict_iommu;
> +static int vmw_force_coherent;
>  
>  static int vmw_probe(struct pci_dev *, const struct pci_device_id *);
>  static void vmw_master_init(struct vmw_master *);
> @@ -193,6 +197,13 @@ static int vmwgfx_pm_notifier(struct notifier_block *nb, unsigned long val,
>  
>  MODULE_PARM_DESC(enable_fbdev, "Enable vmwgfx fbdev");
>  module_param_named(enable_fbdev, enable_fbdev, int, 0600);
> +MODULE_PARM_DESC(force_dma_api, "Force using the DMA API for TTM pages");
> +module_param_named(force_dma_api, vmw_force_iommu, int, 0600);
> +MODULE_PARM_DESC(restrict_iommu, "Try to limit IOMMU usage for TTM pages");
> +module_param_named(restrict_iommu, vmw_restrict_iommu, int, 0600);
> +MODULE_PARM_DESC(force_coherent, "Force coherent TTM pages");
> +module_param_named(force_coherent, vmw_force_coherent, int, 0600);
> +
>  
>  static void vmw_print_capabilities(uint32_t capabilities)
>  {
> @@ -427,12 +438,78 @@ static void vmw_get_initial_size(struct vmw_private *dev_priv)
>  	dev_priv->initial_height = height;
>  }
>  
> +/**
> + * vmw_dma_select_mode - Determine how DMA mappings should be set up for this
> + * system.
> + *
> + * @dev_priv: Pointer to a struct vmw_private
> + *
> + * This functions tries to determine the IOMMU setup and what actions
> + * need to be taken by the driver to make system pages visible to the
> + * device.
> + * If this function decides that DMA is not possible, it returns -EINVAL.
> + * The driver may then try to disable features of the device that require
> + * DMA.
> + */
> +static int vmw_dma_select_mode(struct vmw_private *dev_priv)
> +{
> +	const struct dma_map_ops *dma_ops = get_dma_ops(dev_priv->dev->dev);
> +	static const char *names[vmw_dma_map_max] = {
> +		[vmw_dma_phys] = "Using physical TTM page addresses.",
> +		[vmw_dma_alloc_coherent] = "Using coherent TTM pages.",
> +		[vmw_dma_map_populate] = "Keeping DMA mappings.",
> +		[vmw_dma_map_bind] = "Giving up DMA mappings early."};
> +
> +#ifdef CONFIG_INTEL_IOMMU
> +	if (intel_iommu_enabled) {
> +		dev_priv->map_mode = vmw_dma_map_populate;
> +		goto out_fixup;
> +	}
> +#endif
> +
> +	if (!(vmw_force_iommu || vmw_force_coherent)) {
> +		dev_priv->map_mode = vmw_dma_phys;
> +		DRM_INFO("DMA map mode: %s\n", names[dev_priv->map_mode]);
> +		return 0;
> +	}
> +
> +	dev_priv->map_mode = vmw_dma_map_populate;
> +
> +	if (dma_ops->sync_single_for_cpu)
> +		dev_priv->map_mode = vmw_dma_alloc_coherent;
> +#ifdef CONFIG_SWIOTLB
> +	if (swiotlb_nr_tbl() == 0)
> +		dev_priv->map_mode = vmw_dma_map_populate;
> +#endif
> +
> +out_fixup:
> +	if (dev_priv->map_mode == vmw_dma_map_populate &&
> +	    vmw_restrict_iommu)
> +		dev_priv->map_mode = vmw_dma_map_bind;
> +
> +	if (vmw_force_coherent)
> +		dev_priv->map_mode = vmw_dma_alloc_coherent;
> +
> +#if !defined(CONFIG_SWIOTLB) && !defined(CONFIG_INTEL_IOMMU)
> +	/*
> +	 * No coherent page pool
> +	 */
> +	if (dev_priv->map_mode == vmw_dma_alloc_coherent)
> +		return -EINVAL;
> +#endif
> +
> +	DRM_INFO("DMA map mode: %s\n", names[dev_priv->map_mode]);
> +
> +	return 0;
> +}
> +
>  static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>  {
>  	struct vmw_private *dev_priv;
>  	int ret;
>  	uint32_t svga_id;
>  	enum vmw_res_type i;
> +	bool refuse_dma = false;
>  
>  	dev_priv = kzalloc(sizeof(*dev_priv), GFP_KERNEL);
>  	if (unlikely(dev_priv == NULL)) {
> @@ -481,6 +558,11 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>  	}
>  
>  	dev_priv->capabilities = vmw_read(dev_priv, SVGA_REG_CAPABILITIES);
> +	ret = vmw_dma_select_mode(dev_priv);
> +	if (unlikely(ret != 0)) {
> +		DRM_INFO("Restricting capabilities due to IOMMU setup.\n");
> +		refuse_dma = true;
> +	}
>  
>  	dev_priv->vram_size = vmw_read(dev_priv, SVGA_REG_VRAM_SIZE);
>  	dev_priv->mmio_size = vmw_read(dev_priv, SVGA_REG_MEM_SIZE);
> @@ -558,8 +640,9 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>  	}
>  
>  	dev_priv->has_gmr = true;
> -	if (ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_GMR,
> -			   dev_priv->max_gmr_ids) != 0) {
> +	if (((dev_priv->capabilities & (SVGA_CAP_GMR | SVGA_CAP_GMR2)) == 0) ||
> +	    refuse_dma || ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_GMR,
> +					 dev_priv->max_gmr_ids) != 0) {
>  		DRM_INFO("No GMR memory available. "
>  			 "Graphics memory resources are very limited.\n");
>  		dev_priv->has_gmr = false;
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> index 150ec64..e401d5d 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> @@ -177,6 +177,58 @@ struct vmw_res_cache_entry {
>  	struct vmw_resource_val_node *node;
>  };
>  
> +/**
> + * enum vmw_dma_map_mode - indicate how to perform TTM page dma mappings.
> + */
> +enum vmw_dma_map_mode {
> +	vmw_dma_phys,           /* Use physical page addresses */
> +	vmw_dma_alloc_coherent, /* Use TTM coherent pages */
> +	vmw_dma_map_populate,   /* Unmap from DMA just after unpopulate */
> +	vmw_dma_map_bind,       /* Unmap from DMA just before unbind */
> +	vmw_dma_map_max
> +};
> +
> +/**
> + * struct vmw_sg_table - Scatter/gather table for binding, with additional
> + * device-specific information.
> + *
> + * @sgt: Pointer to a struct sg_table with binding information
> + * @num_regions: Number of regions with device-address contigous pages
> + */
> +struct vmw_sg_table {
> +	enum vmw_dma_map_mode mode;
> +	struct page **pages;
> +	const dma_addr_t *addrs;
> +	struct sg_table *sgt;
> +	unsigned long num_regions;
> +	unsigned long num_pages;
> +};
> +
> +/**
> + * struct vmw_piter - Page iterator that iterates over a list of pages
> + * and DMA addresses that could be either a scatter-gather list or
> + * arrays
> + *
> + * @pages: Array of page pointers to the pages.
> + * @addrs: DMA addresses to the pages if coherent pages are used.
> + * @iter: Scatter-gather page iterator. Current position in SG list.
> + * @i: Current position in arrays.
> + * @num_pages: Number of pages total.
> + * @next: Function to advance the iterator. Returns false if past the list
> + * of pages, true otherwise.
> + * @dma_address: Function to return the DMA address of the current page.
> + */
> +struct vmw_piter {
> +	struct page **pages;
> +	const dma_addr_t *addrs;
> +	struct sg_page_iter iter;
> +	unsigned long i;
> +	unsigned long num_pages;
> +	bool (*next)(struct vmw_piter *);
> +	dma_addr_t (*dma_address)(struct vmw_piter *);
> +	struct page *(*page)(struct vmw_piter *);
> +};
> +
>  struct vmw_sw_context{
>  	struct drm_open_hash res_ht;
>  	bool res_ht_initialized;
> @@ -358,6 +410,11 @@ struct vmw_private {
>  
>  	struct list_head res_lru[vmw_res_max];
>  	uint32_t used_memory_size;
> +
> +	/*
> +	 * DMA mapping stuff.
> +	 */
> +	enum vmw_dma_map_mode map_mode;
>  };
>  
>  static inline struct vmw_surface *vmw_res_to_srf(struct vmw_resource *res)
> @@ -405,7 +462,7 @@ void vmw_3d_resource_dec(struct vmw_private *dev_priv, bool hide_svga);
>   */
>  
>  extern int vmw_gmr_bind(struct vmw_private *dev_priv,
> -			struct page *pages[],
> +			const struct vmw_sg_table *vsgt,
>  			unsigned long num_pages,
>  			int gmr_id);
>  extern void vmw_gmr_unbind(struct vmw_private *dev_priv, int gmr_id);
> @@ -568,6 +625,45 @@ extern struct ttm_placement vmw_evictable_placement;
>  extern struct ttm_placement vmw_srf_placement;
>  extern struct ttm_bo_driver vmw_bo_driver;
>  extern int vmw_dma_quiescent(struct drm_device *dev);
> +extern void vmw_piter_start(struct vmw_piter *viter,
> +			    const struct vmw_sg_table *vsgt,
> +			    unsigned long p_offs);
> +
> +/**
> + * vmw_piter_next - Advance the iterator one page.
> + *
> + * @viter: Pointer to the iterator to advance.
> + *
> + * Returns false if past the list of pages, true otherwise.
> + */
> +static inline bool vmw_piter_next(struct vmw_piter *viter)
> +{
> +	return viter->next(viter);
> +}
> +
> +/**
> + * vmw_piter_dma_addr - Return the DMA address of the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * Returns the DMA address of the page pointed to by @viter.
> + */
> +static inline dma_addr_t vmw_piter_dma_addr(struct vmw_piter *viter)
> +{
> +	return viter->dma_address(viter);
> +}
> +
> +/**
> + * vmw_piter_page - Return a pointer to the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * Returns the DMA address of the page pointed to by @viter.
> + */
> +static inline struct page *vmw_piter_page(struct vmw_piter *viter)
> +{
> +	return viter->page(viter);
> +}
>  
>  /**
>   * Command submission - vmwgfx_execbuf.c
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c b/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
> index 1a0bf07..6d09523 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
> @@ -32,9 +32,11 @@
>  #define VMW_PPN_SIZE (sizeof(unsigned long))
>  /* A future safe maximum remap size. */
>  #define VMW_PPN_PER_REMAP ((31 * 1024) / VMW_PPN_SIZE)
> +#define DMA_ADDR_INVALID ((dma_addr_t) 0)
> +#define DMA_PAGE_INVALID 0UL
>  
>  static int vmw_gmr2_bind(struct vmw_private *dev_priv,
> -			 struct page *pages[],
> +			 struct vmw_piter *iter,
>  			 unsigned long num_pages,
>  			 int gmr_id)
>  {
> @@ -81,11 +83,13 @@ static int vmw_gmr2_bind(struct vmw_private *dev_priv,
>  
>  		for (i = 0; i < nr; ++i) {
>  			if (VMW_PPN_SIZE <= 4)
> -				*cmd = page_to_pfn(*pages++);
> +				*cmd = vmw_piter_dma_addr(iter) >> PAGE_SHIFT;
>  			else
> -				*((uint64_t *)cmd) = page_to_pfn(*pages++);
> +				*((uint64_t *)cmd) = vmw_piter_dma_addr(iter) >>
> +					PAGE_SHIFT;
>  
>  			cmd += VMW_PPN_SIZE / sizeof(*cmd);
> +			vmw_piter_next(iter);
>  		}
>  
>  		num_pages -= nr;
> @@ -120,22 +124,54 @@ static void vmw_gmr2_unbind(struct vmw_private *dev_priv,
>  	vmw_fifo_commit(dev_priv, define_size);
>  }
>  
> +
> +static void vmw_gmr_free_descriptors(struct device *dev, dma_addr_t desc_dma,
> +				     struct list_head *desc_pages)
> +{
> +	struct page *page, *next;
> +	struct svga_guest_mem_descriptor *page_virtual;
> +	unsigned int desc_per_page = PAGE_SIZE /
> +		sizeof(struct svga_guest_mem_descriptor) - 1;
> +
> +	if (list_empty(desc_pages))
> +		return;
> +
> +	list_for_each_entry_safe(page, next, desc_pages, lru) {
> +		list_del_init(&page->lru);
> +
> +		if (likely(desc_dma != DMA_ADDR_INVALID)) {
> +			dma_unmap_page(dev, desc_dma, PAGE_SIZE,
> +				       DMA_TO_DEVICE);
> +		}
> +
> +		page_virtual = kmap_atomic(page);
> +		desc_dma = page_virtual[desc_per_page].ppn << PAGE_SHIFT;
> +		kunmap_atomic(page_virtual);
> +
> +		__free_page(page);
> +	}
> +}
> +
>  /**
>   * FIXME: Adjust to the ttm lowmem / highmem storage to minimize
>   * the number of used descriptors.
> + *
>   */
>  
> -static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
> -				     struct page *pages[],
> -				     unsigned long num_pages)
> +static int vmw_gmr_build_descriptors(struct device *dev,
> +				     struct list_head *desc_pages,
> +				     struct vmw_piter *iter,
> +				     unsigned long num_pages,
> +				     dma_addr_t *first_dma)
>  {
> -	struct page *page, *next;
> +	struct page *page;
>  	struct svga_guest_mem_descriptor *page_virtual = NULL;
>  	struct svga_guest_mem_descriptor *desc_virtual = NULL;
>  	unsigned int desc_per_page;
>  	unsigned long prev_pfn;
>  	unsigned long pfn;
>  	int ret;
> +	dma_addr_t desc_dma;
>  
>  	desc_per_page = PAGE_SIZE /
>  	    sizeof(struct svga_guest_mem_descriptor) - 1;
> @@ -148,23 +184,12 @@ static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
>  		}
>  
>  		list_add_tail(&page->lru, desc_pages);
> -
> -		/*
> -		 * Point previous page terminating descriptor to this
> -		 * page before unmapping it.
> -		 */
> -
> -		if (likely(page_virtual != NULL)) {
> -			desc_virtual->ppn = page_to_pfn(page);
> -			kunmap_atomic(page_virtual);
> -		}
> -
>  		page_virtual = kmap_atomic(page);
>  		desc_virtual = page_virtual - 1;
>  		prev_pfn = ~(0UL);
>  
>  		while (likely(num_pages != 0)) {
> -			pfn = page_to_pfn(*pages);
> +			pfn = vmw_piter_dma_addr(iter) >> PAGE_SHIFT;
>  
>  			if (pfn != prev_pfn + 1) {
>  
> @@ -181,104 +206,81 @@ static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
>  			}
>  			prev_pfn = pfn;
>  			--num_pages;
> -			++pages;
> +			vmw_piter_next(iter);
>  		}
>  
> -		(++desc_virtual)->ppn = cpu_to_le32(0);
> +		(++desc_virtual)->ppn = DMA_PAGE_INVALID;
>  		desc_virtual->num_pages = cpu_to_le32(0);
> +		kunmap_atomic(page_virtual);
>  	}
>  
> -	if (likely(page_virtual != NULL))
> +	desc_dma = 0;
> +	list_for_each_entry_reverse(page, desc_pages, lru) {
> +		page_virtual = kmap_atomic(page);
> +		page_virtual[desc_per_page].ppn = desc_dma >> PAGE_SHIFT;
>  		kunmap_atomic(page_virtual);
> +		desc_dma = dma_map_page(dev, page, 0, PAGE_SIZE,
> +					DMA_TO_DEVICE);
> +
> +		if (unlikely(dma_mapping_error(dev, desc_dma)))
> +			goto out_err;
> +	}
> +	*first_dma = desc_dma;
>  
>  	return 0;
>  out_err:
> -	list_for_each_entry_safe(page, next, desc_pages, lru) {
> -		list_del_init(&page->lru);
> -		__free_page(page);
> -	}
> +	vmw_gmr_free_descriptors(dev, DMA_ADDR_INVALID, desc_pages);
>  	return ret;
>  }
>  
> -static inline void vmw_gmr_free_descriptors(struct list_head *desc_pages)
> -{
> -	struct page *page, *next;
> -
> -	list_for_each_entry_safe(page, next, desc_pages, lru) {
> -		list_del_init(&page->lru);
> -		__free_page(page);
> -	}
> -}
> -
>  static void vmw_gmr_fire_descriptors(struct vmw_private *dev_priv,
> -				     int gmr_id, struct list_head *desc_pages)
> +				     int gmr_id, dma_addr_t desc_dma)
>  {
> -	struct page *page;
> -
> -	if (unlikely(list_empty(desc_pages)))
> -		return;
> -
> -	page = list_entry(desc_pages->next, struct page, lru);
> -
>  	mutex_lock(&dev_priv->hw_mutex);
>  
>  	vmw_write(dev_priv, SVGA_REG_GMR_ID, gmr_id);
>  	wmb();
> -	vmw_write(dev_priv, SVGA_REG_GMR_DESCRIPTOR, page_to_pfn(page));
> +	vmw_write(dev_priv, SVGA_REG_GMR_DESCRIPTOR, desc_dma >> PAGE_SHIFT);
>  	mb();
>  
>  	mutex_unlock(&dev_priv->hw_mutex);
>  
>  }
>  
> -/**
> - * FIXME: Adjust to the ttm lowmem / highmem storage to minimize
> - * the number of used descriptors.
> - */
> -
> -static unsigned long vmw_gmr_count_descriptors(struct page *pages[],
> -					unsigned long num_pages)
> -{
> -	unsigned long prev_pfn = ~(0UL);
> -	unsigned long pfn;
> -	unsigned long descriptors = 0;
> -
> -	while (num_pages--) {
> -		pfn = page_to_pfn(*pages++);
> -		if (prev_pfn + 1 != pfn)
> -			++descriptors;
> -		prev_pfn = pfn;
> -	}
> -
> -	return descriptors;
> -}
> -
>  int vmw_gmr_bind(struct vmw_private *dev_priv,
> -		 struct page *pages[],
> +		 const struct vmw_sg_table *vsgt,
>  		 unsigned long num_pages,
>  		 int gmr_id)
>  {
>  	struct list_head desc_pages;
> +	dma_addr_t desc_dma = 0;
> +	struct device *dev = dev_priv->dev->dev;
> +	struct vmw_piter data_iter;
>  	int ret;
>  
> +	vmw_piter_start(&data_iter, vsgt, 0);
> +
> +	if (unlikely(!vmw_piter_next(&data_iter)))
> +		return 0;
> +
>  	if (likely(dev_priv->capabilities & SVGA_CAP_GMR2))
> -		return vmw_gmr2_bind(dev_priv, pages, num_pages, gmr_id);
> +		return vmw_gmr2_bind(dev_priv, &data_iter, num_pages, gmr_id);
>  
>  	if (unlikely(!(dev_priv->capabilities & SVGA_CAP_GMR)))
>  		return -EINVAL;
>  
> -	if (vmw_gmr_count_descriptors(pages, num_pages) >
> -	    dev_priv->max_gmr_descriptors)
> +	if (vsgt->num_regions > dev_priv->max_gmr_descriptors)
>  		return -EINVAL;
>  
>  	INIT_LIST_HEAD(&desc_pages);
>  
> -	ret = vmw_gmr_build_descriptors(&desc_pages, pages, num_pages);
> +	ret = vmw_gmr_build_descriptors(dev, &desc_pages, &data_iter,
> +					num_pages, &desc_dma);
>  	if (unlikely(ret != 0))
>  		return ret;
>  
> -	vmw_gmr_fire_descriptors(dev_priv, gmr_id, &desc_pages);
> -	vmw_gmr_free_descriptors(&desc_pages);
> +	vmw_gmr_fire_descriptors(dev_priv, gmr_id, desc_dma);
> +	vmw_gmr_free_descriptors(dev, desc_dma, &desc_pages);
>  
>  	return 0;
>  }
> -- 
> 1.7.10.4
> 
> ------------------------------------------------------------------------------
> Android is increasing in popularity, but the open development platform that
> developers love is also attractive to malware creators. Download this white
> paper to learn more about secure code signing practices that can help keep
> Android apps secure.
> http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk
> --
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+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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Re: [PATCH 0/2] Make the vmwgfx driver reasonably DMA-API compliant

[Konrad Rzeszutek Wilk]

On Mon, Nov 04, 2013 at 05:57:37AM -0800, Thomas Hellstrom wrote:
> These patches makes the vmwgfx driver use the DMA API to obtain valid
> device addresses rather than blindly using physical addresses.
> 
> The main motivation is to be able to use a virtual IOMMU in the future.

Ooooh. Neat! Are there any RFC patches available?
> 
> Other TTM drivers typically map pages one by one rather than using a
> scatter-gather list, but since we can benefit from having a single dma
> address region set up by the IOMMU, we use a scatter-gather list instead.
> 
> Finally to be able to handle all the dma mapping modes, we locally extend the
> scatter-gather list page iterator to handle also the direct physical- and
> coherent cases.
> 
> Finally, the TTM DMA page pool is enabled also when the Intel IOMMU is active

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Re: [PATCH 1/2] drm/ttm: Enable the dma page pool also for intel IOMMUs

[Konrad Rzeszutek Wilk]

On Mon, Nov 04, 2013 at 05:57:38AM -0800, Thomas Hellstrom wrote:
> Used by the vmwgfx driver

That looks OK to me. And baremetal should not be
affected as the Intel VT-d driver turns of the SWIOTLB
driver - so it will still use the classic ttm pool code.

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

> 
> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
> ---
>  drivers/gpu/drm/ttm/Makefile             |    6 +-----
>  drivers/gpu/drm/ttm/ttm_page_alloc_dma.c |    3 +++
>  include/drm/ttm/ttm_page_alloc.h         |   11 ++++++++++-
>  3 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
> index b2b33dd..b433b9f 100644
> --- a/drivers/gpu/drm/ttm/Makefile
> +++ b/drivers/gpu/drm/ttm/Makefile
> @@ -5,10 +5,6 @@ ccflags-y := -Iinclude/drm
>  ttm-y := ttm_agp_backend.o ttm_memory.o ttm_tt.o ttm_bo.o \
>  	ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
>  	ttm_object.o ttm_lock.o ttm_execbuf_util.o ttm_page_alloc.o \
> -	ttm_bo_manager.o
> -
> -ifeq ($(CONFIG_SWIOTLB),y)
> -ttm-y += ttm_page_alloc_dma.o
> -endif
> +	ttm_bo_manager.o ttm_page_alloc_dma.o
>  
>  obj-$(CONFIG_DRM_TTM) += ttm.o
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> index 7957bee..fb8259f 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> @@ -33,6 +33,7 @@
>   *   when freed).
>   */
>  
> +#if defined(CONFIG_SWIOTLB) || defined(CONFIG_INTEL_IOMMU)
>  #define pr_fmt(fmt) "[TTM] " fmt
>  
>  #include <linux/dma-mapping.h>
> @@ -1142,3 +1143,5 @@ int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data)
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(ttm_dma_page_alloc_debugfs);
> +
> +#endif
> diff --git a/include/drm/ttm/ttm_page_alloc.h b/include/drm/ttm/ttm_page_alloc.h
> index 706b962..d1f61bf 100644
> --- a/include/drm/ttm/ttm_page_alloc.h
> +++ b/include/drm/ttm/ttm_page_alloc.h
> @@ -62,7 +62,7 @@ extern void ttm_pool_unpopulate(struct ttm_tt *ttm);
>  extern int ttm_page_alloc_debugfs(struct seq_file *m, void *data);
>  
>  
> -#ifdef CONFIG_SWIOTLB
> +#if defined(CONFIG_SWIOTLB) || defined(CONFIG_INTEL_IOMMU)
>  /**
>   * Initialize pool allocator.
>   */
> @@ -94,6 +94,15 @@ static inline int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data)
>  {
>  	return 0;
>  }
> +static inline int ttm_dma_populate(struct ttm_dma_tt *ttm_dma,
> +				   struct device *dev)
> +{
> +	return -ENOMEM;
> +}
> +static inline void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma,
> +				      struct device *dev)
> +{
> +}
>  #endif
>  
>  #endif
> -- 
> 1.7.10.4

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Re: [PATCH 2/2] drm/vmwgfx: Use the linux DMA api to get valid device addresses of pages

[Konrad Rzeszutek Wilk]

On Mon, Nov 04, 2013 at 05:57:39AM -0800, Thomas Hellstrom wrote:
> The code handles three different cases:
> 1) physical page addresses. The ttm page array is used.
> 2) DMA subsystem addresses. A scatter-gather list is used.
> 3) Coherent pages. The ttm dma pool is used, together with the dma_ttm
> array os dma_addr_t
> 
> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

I looked at it from the TTM DMA perspective and it looks OK for me.

> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c |  379 ++++++++++++++++++++++++++++++--
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    |   87 +++++++-
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h    |   98 ++++++++-
>  drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c    |  150 ++++++-------
>  4 files changed, 620 insertions(+), 94 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
> index 96dc84d..7776e6f 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
> @@ -141,37 +141,374 @@ struct ttm_placement vmw_srf_placement = {
>  };
>  
>  struct vmw_ttm_tt {
> -	struct ttm_tt ttm;
> +	struct ttm_dma_tt dma_ttm;
>  	struct vmw_private *dev_priv;
>  	int gmr_id;
> +	struct sg_table sgt;
> +	struct vmw_sg_table vsgt;
> +	uint64_t sg_alloc_size;
> +	bool mapped;
>  };
>  
> +/**
> + * Helper functions to advance a struct vmw_piter iterator.
> + *
> + * @viter: Pointer to the iterator.
> + *
> + * These functions return false if past the end of the list,
> + * true otherwise. Functions are selected depending on the current
> + * DMA mapping mode.
> + */
> +static bool __vmw_piter_non_sg_next(struct vmw_piter *viter)
> +{
> +	return ++(viter->i) < viter->num_pages;
> +}
> +
> +static bool __vmw_piter_sg_next(struct vmw_piter *viter)
> +{
> +	return __sg_page_iter_next(&viter->iter);
> +}
> +
> +
> +/**
> + * Helper functions to return a pointer to the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * These functions return a pointer to the page currently
> + * pointed to by @viter. Functions are selected depending on the
> + * current mapping mode.
> + */
> +static struct page *__vmw_piter_non_sg_page(struct vmw_piter *viter)
> +{
> +	return viter->pages[viter->i];
> +}
> +
> +static struct page *__vmw_piter_sg_page(struct vmw_piter *viter)
> +{
> +	return sg_page_iter_page(&viter->iter);
> +}
> +
> +
> +/**
> + * Helper functions to return the DMA address of the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * These functions return the DMA address of the page currently
> + * pointed to by @viter. Functions are selected depending on the
> + * current mapping mode.
> + */
> +static dma_addr_t __vmw_piter_phys_addr(struct vmw_piter *viter)
> +{
> +	return page_to_phys(viter->pages[viter->i]);
> +}
> +
> +static dma_addr_t __vmw_piter_dma_addr(struct vmw_piter *viter)
> +{
> +	return viter->addrs[viter->i];
> +}
> +
> +static dma_addr_t __vmw_piter_sg_addr(struct vmw_piter *viter)
> +{
> +	return sg_page_iter_dma_address(&viter->iter);
> +}
> +
> +
> +/**
> + * vmw_piter_start - Initialize a struct vmw_piter.
> + *
> + * @viter: Pointer to the iterator to initialize
> + * @vsgt: Pointer to a struct vmw_sg_table to initialize from
> + *
> + * Note that we're following the convention of __sg_page_iter_start, so that
> + * the iterator doesn't point to a valid page after initialization; it has
> + * to be advanced one step first.
> + */
> +void vmw_piter_start(struct vmw_piter *viter, const struct vmw_sg_table *vsgt,
> +		     unsigned long p_offset)
> +{
> +	viter->i = p_offset - 1;
> +	viter->num_pages = vsgt->num_pages;
> +	switch (vsgt->mode) {
> +	case vmw_dma_phys:
> +		viter->next = &__vmw_piter_non_sg_next;
> +		viter->dma_address = &__vmw_piter_phys_addr;
> +		viter->page = &__vmw_piter_non_sg_page;
> +		viter->pages = vsgt->pages;
> +		break;
> +	case vmw_dma_alloc_coherent:
> +		viter->next = &__vmw_piter_non_sg_next;
> +		viter->dma_address = &__vmw_piter_dma_addr;
> +		viter->page = &__vmw_piter_non_sg_page;
> +		viter->addrs = vsgt->addrs;
> +		break;
> +	case vmw_dma_map_populate:
> +	case vmw_dma_map_bind:
> +		viter->next = &__vmw_piter_sg_next;
> +		viter->dma_address = &__vmw_piter_sg_addr;
> +		viter->page = &__vmw_piter_sg_page;
> +		__sg_page_iter_start(&viter->iter, vsgt->sgt->sgl,
> +				     vsgt->sgt->orig_nents, p_offset);
> +		break;
> +	default:
> +		BUG();
> +	}
> +}
> +
> +/**
> + * vmw_ttm_unmap_from_dma - unmap  device addresses previsouly mapped for
> + * TTM pages
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_backend
> + *
> + * Used to free dma mappings previously mapped by vmw_ttm_map_for_dma.
> + */
> +static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct device *dev = vmw_tt->dev_priv->dev->dev;
> +
> +	dma_unmap_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.nents,
> +		DMA_BIDIRECTIONAL);
> +	vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents;
> +}
> +
> +/**
> + * vmw_ttm_map_for_dma - map TTM pages to get device addresses
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_backend
> + *
> + * This function is used to get device addresses from the kernel DMA layer.
> + * However, it's violating the DMA API in that when this operation has been
> + * performed, it's illegal for the CPU to write to the pages without first
> + * unmapping the DMA mappings, or calling dma_sync_sg_for_cpu(). It is
> + * therefore only legal to call this function if we know that the function
> + * dma_sync_sg_for_cpu() is a NOP, and dma_sync_sg_for_device() is at most
> + * a CPU write buffer flush.
> + */
> +static int vmw_ttm_map_for_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct device *dev = vmw_tt->dev_priv->dev->dev;
> +	int ret;
> +
> +	ret = dma_map_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.orig_nents,
> +			 DMA_BIDIRECTIONAL);
> +	if (unlikely(ret == 0))
> +		return -ENOMEM;
> +
> +	vmw_tt->sgt.nents = ret;
> +
> +	return 0;
> +}
> +
> +/**
> + * vmw_ttm_map_dma - Make sure TTM pages are visible to the device
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_tt
> + *
> + * Select the correct function for and make sure the TTM pages are
> + * visible to the device. Allocate storage for the device mappings.
> + * If a mapping has already been performed, indicated by the storage
> + * pointer being non NULL, the function returns success.
> + */
> +static int vmw_ttm_map_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
> +	struct vmw_sg_table *vsgt = &vmw_tt->vsgt;
> +	struct vmw_piter iter;
> +	dma_addr_t old;
> +	int ret = 0;
> +	static size_t sgl_size;
> +	static size_t sgt_size;
> +
> +	if (vmw_tt->mapped)
> +		return 0;
> +
> +	vsgt->mode = dev_priv->map_mode;
> +	vsgt->pages = vmw_tt->dma_ttm.ttm.pages;
> +	vsgt->num_pages = vmw_tt->dma_ttm.ttm.num_pages;
> +	vsgt->addrs = vmw_tt->dma_ttm.dma_address;
> +	vsgt->sgt = &vmw_tt->sgt;
> +
> +	switch (dev_priv->map_mode) {
> +	case vmw_dma_map_bind:
> +	case vmw_dma_map_populate:
> +		if (unlikely(!sgl_size)) {
> +			sgl_size = ttm_round_pot(sizeof(struct scatterlist));
> +			sgt_size = ttm_round_pot(sizeof(struct sg_table));
> +		}
> +		vmw_tt->sg_alloc_size = sgt_size + sgl_size * vsgt->num_pages;
> +		ret = ttm_mem_global_alloc(glob, vmw_tt->sg_alloc_size, false,
> +					   true);
> +		if (unlikely(ret != 0))
> +			return ret;
> +
> +		ret = sg_alloc_table_from_pages(&vmw_tt->sgt, vsgt->pages,
> +						vsgt->num_pages, 0,
> +						(unsigned long)
> +						vsgt->num_pages << PAGE_SHIFT,
> +						GFP_KERNEL);
> +		if (unlikely(ret != 0))
> +			goto out_sg_alloc_fail;
> +
> +		if (vsgt->num_pages > vmw_tt->sgt.nents) {
> +			uint64_t over_alloc =
> +				sgl_size * (vsgt->num_pages -
> +					    vmw_tt->sgt.nents);
> +
> +			ttm_mem_global_free(glob, over_alloc);
> +			vmw_tt->sg_alloc_size -= over_alloc;
> +		}
> +
> +		ret = vmw_ttm_map_for_dma(vmw_tt);
> +		if (unlikely(ret != 0))
> +			goto out_map_fail;
> +
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	old = ~((dma_addr_t) 0);
> +	vmw_tt->vsgt.num_regions = 0;
> +	for (vmw_piter_start(&iter, vsgt, 0); vmw_piter_next(&iter);) {
> +		dma_addr_t cur = vmw_piter_dma_addr(&iter);
> +
> +		if (cur != old + PAGE_SIZE)
> +			vmw_tt->vsgt.num_regions++;
> +		old = cur;
> +	}
> +
> +	vmw_tt->mapped = true;
> +	return 0;
> +
> +out_map_fail:
> +	sg_free_table(vmw_tt->vsgt.sgt);
> +	vmw_tt->vsgt.sgt = NULL;
> +out_sg_alloc_fail:
> +	ttm_mem_global_free(glob, vmw_tt->sg_alloc_size);
> +	return ret;
> +}
> +
> +/**
> + * vmw_ttm_unmap_dma - Tear down any TTM page device mappings
> + *
> + * @vmw_tt: Pointer to a struct vmw_ttm_tt
> + *
> + * Tear down any previously set up device DMA mappings and free
> + * any storage space allocated for them. If there are no mappings set up,
> + * this function is a NOP.
> + */
> +static void vmw_ttm_unmap_dma(struct vmw_ttm_tt *vmw_tt)
> +{
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +
> +	if (!vmw_tt->vsgt.sgt)
> +		return;
> +
> +	switch (dev_priv->map_mode) {
> +	case vmw_dma_map_bind:
> +	case vmw_dma_map_populate:
> +		vmw_ttm_unmap_from_dma(vmw_tt);
> +		sg_free_table(vmw_tt->vsgt.sgt);
> +		vmw_tt->vsgt.sgt = NULL;
> +		ttm_mem_global_free(vmw_mem_glob(dev_priv),
> +				    vmw_tt->sg_alloc_size);
> +		break;
> +	default:
> +		break;
> +	}
> +	vmw_tt->mapped = false;
> +}
> +
>  static int vmw_ttm_bind(struct ttm_tt *ttm, struct ttm_mem_reg *bo_mem)
>  {
> -	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
> +	struct vmw_ttm_tt *vmw_be =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
> +	int ret;
> +
> +	ret = vmw_ttm_map_dma(vmw_be);
> +	if (unlikely(ret != 0))
> +		return ret;
>  
>  	vmw_be->gmr_id = bo_mem->start;
>  
> -	return vmw_gmr_bind(vmw_be->dev_priv, ttm->pages,
> +	return vmw_gmr_bind(vmw_be->dev_priv, &vmw_be->vsgt,
>  			    ttm->num_pages, vmw_be->gmr_id);
>  }
>  
>  static int vmw_ttm_unbind(struct ttm_tt *ttm)
>  {
> -	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
> +	struct vmw_ttm_tt *vmw_be =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
>  
>  	vmw_gmr_unbind(vmw_be->dev_priv, vmw_be->gmr_id);
> +
> +	if (vmw_be->dev_priv->map_mode == vmw_dma_map_bind)
> +		vmw_ttm_unmap_dma(vmw_be);
> +
>  	return 0;
>  }
>  
>  static void vmw_ttm_destroy(struct ttm_tt *ttm)
>  {
> -	struct vmw_ttm_tt *vmw_be = container_of(ttm, struct vmw_ttm_tt, ttm);
> -
> -	ttm_tt_fini(ttm);
> +	struct vmw_ttm_tt *vmw_be =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
> +
> +	vmw_ttm_unmap_dma(vmw_be);
> +	if (vmw_be->dev_priv->map_mode == vmw_dma_alloc_coherent)
> +		ttm_dma_tt_fini(&vmw_be->dma_ttm);
> +	else
> +		ttm_tt_fini(ttm);
>  	kfree(vmw_be);
>  }
>  
> +static int vmw_ttm_populate(struct ttm_tt *ttm)
> +{
> +	struct vmw_ttm_tt *vmw_tt =
> +		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
> +	int ret;
> +
> +	if (ttm->state != tt_unpopulated)
> +		return 0;
> +
> +	if (dev_priv->map_mode == vmw_dma_alloc_coherent) {
> +		size_t size =
> +			ttm_round_pot(ttm->num_pages * sizeof(dma_addr_t));
> +		ret = ttm_mem_global_alloc(glob, size, false, true);
> +		if (unlikely(ret != 0))
> +			return ret;
> +
> +		ret = ttm_dma_populate(&vmw_tt->dma_ttm, dev_priv->dev->dev);
> +		if (unlikely(ret != 0))
> +			ttm_mem_global_free(glob, size);
> +	} else
> +		ret = ttm_pool_populate(ttm);
> +
> +	return ret;
> +}
> +
> +static void vmw_ttm_unpopulate(struct ttm_tt *ttm)
> +{
> +	struct vmw_ttm_tt *vmw_tt = container_of(ttm, struct vmw_ttm_tt,
> +						 dma_ttm.ttm);
> +	struct vmw_private *dev_priv = vmw_tt->dev_priv;
> +	struct ttm_mem_global *glob = vmw_mem_glob(dev_priv);
> +
> +	vmw_ttm_unmap_dma(vmw_tt);
> +	if (dev_priv->map_mode == vmw_dma_alloc_coherent) {
> +		size_t size =
> +			ttm_round_pot(ttm->num_pages * sizeof(dma_addr_t));
> +
> +		ttm_dma_unpopulate(&vmw_tt->dma_ttm, dev_priv->dev->dev);
> +		ttm_mem_global_free(glob, size);
> +	} else
> +		ttm_pool_unpopulate(ttm);
> +}
> +
>  static struct ttm_backend_func vmw_ttm_func = {
>  	.bind = vmw_ttm_bind,
>  	.unbind = vmw_ttm_unbind,
> @@ -183,20 +520,28 @@ struct ttm_tt *vmw_ttm_tt_create(struct ttm_bo_device *bdev,
>  				 struct page *dummy_read_page)
>  {
>  	struct vmw_ttm_tt *vmw_be;
> +	int ret;
>  
> -	vmw_be = kmalloc(sizeof(*vmw_be), GFP_KERNEL);
> +	vmw_be = kzalloc(sizeof(*vmw_be), GFP_KERNEL);
>  	if (!vmw_be)
>  		return NULL;
>  
> -	vmw_be->ttm.func = &vmw_ttm_func;
> +	vmw_be->dma_ttm.ttm.func = &vmw_ttm_func;
>  	vmw_be->dev_priv = container_of(bdev, struct vmw_private, bdev);
>  
> -	if (ttm_tt_init(&vmw_be->ttm, bdev, size, page_flags, dummy_read_page)) {
> -		kfree(vmw_be);
> -		return NULL;
> -	}
> -
> -	return &vmw_be->ttm;
> +	if (vmw_be->dev_priv->map_mode == vmw_dma_alloc_coherent)
> +		ret = ttm_dma_tt_init(&vmw_be->dma_ttm, bdev, size, page_flags,
> +				      dummy_read_page);
> +	else
> +		ret = ttm_tt_init(&vmw_be->dma_ttm.ttm, bdev, size, page_flags,
> +				  dummy_read_page);
> +	if (unlikely(ret != 0))
> +		goto out_no_init;
> +
> +	return &vmw_be->dma_ttm.ttm;
> +out_no_init:
> +	kfree(vmw_be);
> +	return NULL;
>  }
>  
>  int vmw_invalidate_caches(struct ttm_bo_device *bdev, uint32_t flags)
> @@ -332,8 +677,8 @@ static int vmw_sync_obj_wait(void *sync_obj, bool lazy, bool interruptible)
>  
>  struct ttm_bo_driver vmw_bo_driver = {
>  	.ttm_tt_create = &vmw_ttm_tt_create,
> -	.ttm_tt_populate = &ttm_pool_populate,
> -	.ttm_tt_unpopulate = &ttm_pool_unpopulate,
> +	.ttm_tt_populate = &vmw_ttm_populate,
> +	.ttm_tt_unpopulate = &vmw_ttm_unpopulate,
>  	.invalidate_caches = vmw_invalidate_caches,
>  	.init_mem_type = vmw_init_mem_type,
>  	.evict_flags = vmw_evict_flags,
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 1a90f0a..0b5c781 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -32,6 +32,7 @@
>  #include <drm/ttm/ttm_bo_driver.h>
>  #include <drm/ttm/ttm_object.h>
>  #include <drm/ttm/ttm_module.h>
> +#include <linux/dma_remapping.h>
>  
>  #define VMWGFX_DRIVER_NAME "vmwgfx"
>  #define VMWGFX_DRIVER_DESC "Linux drm driver for VMware graphics devices"
> @@ -185,6 +186,9 @@ static struct pci_device_id vmw_pci_id_list[] = {
>  MODULE_DEVICE_TABLE(pci, vmw_pci_id_list);
>  
>  static int enable_fbdev = IS_ENABLED(CONFIG_DRM_VMWGFX_FBCON);
> +static int vmw_force_iommu;
> +static int vmw_restrict_iommu;
> +static int vmw_force_coherent;
>  
>  static int vmw_probe(struct pci_dev *, const struct pci_device_id *);
>  static void vmw_master_init(struct vmw_master *);
> @@ -193,6 +197,13 @@ static int vmwgfx_pm_notifier(struct notifier_block *nb, unsigned long val,
>  
>  MODULE_PARM_DESC(enable_fbdev, "Enable vmwgfx fbdev");
>  module_param_named(enable_fbdev, enable_fbdev, int, 0600);
> +MODULE_PARM_DESC(force_dma_api, "Force using the DMA API for TTM pages");
> +module_param_named(force_dma_api, vmw_force_iommu, int, 0600);
> +MODULE_PARM_DESC(restrict_iommu, "Try to limit IOMMU usage for TTM pages");
> +module_param_named(restrict_iommu, vmw_restrict_iommu, int, 0600);
> +MODULE_PARM_DESC(force_coherent, "Force coherent TTM pages");
> +module_param_named(force_coherent, vmw_force_coherent, int, 0600);
> +
>  
>  static void vmw_print_capabilities(uint32_t capabilities)
>  {
> @@ -427,12 +438,78 @@ static void vmw_get_initial_size(struct vmw_private *dev_priv)
>  	dev_priv->initial_height = height;
>  }
>  
> +/**
> + * vmw_dma_select_mode - Determine how DMA mappings should be set up for this
> + * system.
> + *
> + * @dev_priv: Pointer to a struct vmw_private
> + *
> + * This functions tries to determine the IOMMU setup and what actions
> + * need to be taken by the driver to make system pages visible to the
> + * device.
> + * If this function decides that DMA is not possible, it returns -EINVAL.
> + * The driver may then try to disable features of the device that require
> + * DMA.
> + */
> +static int vmw_dma_select_mode(struct vmw_private *dev_priv)
> +{
> +	const struct dma_map_ops *dma_ops = get_dma_ops(dev_priv->dev->dev);
> +	static const char *names[vmw_dma_map_max] = {
> +		[vmw_dma_phys] = "Using physical TTM page addresses.",
> +		[vmw_dma_alloc_coherent] = "Using coherent TTM pages.",
> +		[vmw_dma_map_populate] = "Keeping DMA mappings.",
> +		[vmw_dma_map_bind] = "Giving up DMA mappings early."};
> +
> +#ifdef CONFIG_INTEL_IOMMU
> +	if (intel_iommu_enabled) {
> +		dev_priv->map_mode = vmw_dma_map_populate;
> +		goto out_fixup;
> +	}
> +#endif
> +
> +	if (!(vmw_force_iommu || vmw_force_coherent)) {
> +		dev_priv->map_mode = vmw_dma_phys;
> +		DRM_INFO("DMA map mode: %s\n", names[dev_priv->map_mode]);
> +		return 0;
> +	}
> +
> +	dev_priv->map_mode = vmw_dma_map_populate;
> +
> +	if (dma_ops->sync_single_for_cpu)
> +		dev_priv->map_mode = vmw_dma_alloc_coherent;
> +#ifdef CONFIG_SWIOTLB
> +	if (swiotlb_nr_tbl() == 0)
> +		dev_priv->map_mode = vmw_dma_map_populate;
> +#endif
> +
> +out_fixup:
> +	if (dev_priv->map_mode == vmw_dma_map_populate &&
> +	    vmw_restrict_iommu)
> +		dev_priv->map_mode = vmw_dma_map_bind;
> +
> +	if (vmw_force_coherent)
> +		dev_priv->map_mode = vmw_dma_alloc_coherent;
> +
> +#if !defined(CONFIG_SWIOTLB) && !defined(CONFIG_INTEL_IOMMU)
> +	/*
> +	 * No coherent page pool
> +	 */
> +	if (dev_priv->map_mode == vmw_dma_alloc_coherent)
> +		return -EINVAL;
> +#endif
> +
> +	DRM_INFO("DMA map mode: %s\n", names[dev_priv->map_mode]);
> +
> +	return 0;
> +}
> +
>  static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>  {
>  	struct vmw_private *dev_priv;
>  	int ret;
>  	uint32_t svga_id;
>  	enum vmw_res_type i;
> +	bool refuse_dma = false;
>  
>  	dev_priv = kzalloc(sizeof(*dev_priv), GFP_KERNEL);
>  	if (unlikely(dev_priv == NULL)) {
> @@ -481,6 +558,11 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>  	}
>  
>  	dev_priv->capabilities = vmw_read(dev_priv, SVGA_REG_CAPABILITIES);
> +	ret = vmw_dma_select_mode(dev_priv);
> +	if (unlikely(ret != 0)) {
> +		DRM_INFO("Restricting capabilities due to IOMMU setup.\n");
> +		refuse_dma = true;
> +	}
>  
>  	dev_priv->vram_size = vmw_read(dev_priv, SVGA_REG_VRAM_SIZE);
>  	dev_priv->mmio_size = vmw_read(dev_priv, SVGA_REG_MEM_SIZE);
> @@ -558,8 +640,9 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>  	}
>  
>  	dev_priv->has_gmr = true;
> -	if (ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_GMR,
> -			   dev_priv->max_gmr_ids) != 0) {
> +	if (((dev_priv->capabilities & (SVGA_CAP_GMR | SVGA_CAP_GMR2)) == 0) ||
> +	    refuse_dma || ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_GMR,
> +					 dev_priv->max_gmr_ids) != 0) {
>  		DRM_INFO("No GMR memory available. "
>  			 "Graphics memory resources are very limited.\n");
>  		dev_priv->has_gmr = false;
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> index 150ec64..e401d5d 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> @@ -177,6 +177,58 @@ struct vmw_res_cache_entry {
>  	struct vmw_resource_val_node *node;
>  };
>  
> +/**
> + * enum vmw_dma_map_mode - indicate how to perform TTM page dma mappings.
> + */
> +enum vmw_dma_map_mode {
> +	vmw_dma_phys,           /* Use physical page addresses */
> +	vmw_dma_alloc_coherent, /* Use TTM coherent pages */
> +	vmw_dma_map_populate,   /* Unmap from DMA just after unpopulate */
> +	vmw_dma_map_bind,       /* Unmap from DMA just before unbind */
> +	vmw_dma_map_max
> +};
> +
> +/**
> + * struct vmw_sg_table - Scatter/gather table for binding, with additional
> + * device-specific information.
> + *
> + * @sgt: Pointer to a struct sg_table with binding information
> + * @num_regions: Number of regions with device-address contigous pages
> + */
> +struct vmw_sg_table {
> +	enum vmw_dma_map_mode mode;
> +	struct page **pages;
> +	const dma_addr_t *addrs;
> +	struct sg_table *sgt;
> +	unsigned long num_regions;
> +	unsigned long num_pages;
> +};
> +
> +/**
> + * struct vmw_piter - Page iterator that iterates over a list of pages
> + * and DMA addresses that could be either a scatter-gather list or
> + * arrays
> + *
> + * @pages: Array of page pointers to the pages.
> + * @addrs: DMA addresses to the pages if coherent pages are used.
> + * @iter: Scatter-gather page iterator. Current position in SG list.
> + * @i: Current position in arrays.
> + * @num_pages: Number of pages total.
> + * @next: Function to advance the iterator. Returns false if past the list
> + * of pages, true otherwise.
> + * @dma_address: Function to return the DMA address of the current page.
> + */
> +struct vmw_piter {
> +	struct page **pages;
> +	const dma_addr_t *addrs;
> +	struct sg_page_iter iter;
> +	unsigned long i;
> +	unsigned long num_pages;
> +	bool (*next)(struct vmw_piter *);
> +	dma_addr_t (*dma_address)(struct vmw_piter *);
> +	struct page *(*page)(struct vmw_piter *);
> +};
> +
>  struct vmw_sw_context{
>  	struct drm_open_hash res_ht;
>  	bool res_ht_initialized;
> @@ -358,6 +410,11 @@ struct vmw_private {
>  
>  	struct list_head res_lru[vmw_res_max];
>  	uint32_t used_memory_size;
> +
> +	/*
> +	 * DMA mapping stuff.
> +	 */
> +	enum vmw_dma_map_mode map_mode;
>  };
>  
>  static inline struct vmw_surface *vmw_res_to_srf(struct vmw_resource *res)
> @@ -405,7 +462,7 @@ void vmw_3d_resource_dec(struct vmw_private *dev_priv, bool hide_svga);
>   */
>  
>  extern int vmw_gmr_bind(struct vmw_private *dev_priv,
> -			struct page *pages[],
> +			const struct vmw_sg_table *vsgt,
>  			unsigned long num_pages,
>  			int gmr_id);
>  extern void vmw_gmr_unbind(struct vmw_private *dev_priv, int gmr_id);
> @@ -568,6 +625,45 @@ extern struct ttm_placement vmw_evictable_placement;
>  extern struct ttm_placement vmw_srf_placement;
>  extern struct ttm_bo_driver vmw_bo_driver;
>  extern int vmw_dma_quiescent(struct drm_device *dev);
> +extern void vmw_piter_start(struct vmw_piter *viter,
> +			    const struct vmw_sg_table *vsgt,
> +			    unsigned long p_offs);
> +
> +/**
> + * vmw_piter_next - Advance the iterator one page.
> + *
> + * @viter: Pointer to the iterator to advance.
> + *
> + * Returns false if past the list of pages, true otherwise.
> + */
> +static inline bool vmw_piter_next(struct vmw_piter *viter)
> +{
> +	return viter->next(viter);
> +}
> +
> +/**
> + * vmw_piter_dma_addr - Return the DMA address of the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * Returns the DMA address of the page pointed to by @viter.
> + */
> +static inline dma_addr_t vmw_piter_dma_addr(struct vmw_piter *viter)
> +{
> +	return viter->dma_address(viter);
> +}
> +
> +/**
> + * vmw_piter_page - Return a pointer to the current page.
> + *
> + * @viter: Pointer to the iterator
> + *
> + * Returns the DMA address of the page pointed to by @viter.
> + */
> +static inline struct page *vmw_piter_page(struct vmw_piter *viter)
> +{
> +	return viter->page(viter);
> +}
>  
>  /**
>   * Command submission - vmwgfx_execbuf.c
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c b/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
> index 1a0bf07..6d09523 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gmr.c
> @@ -32,9 +32,11 @@
>  #define VMW_PPN_SIZE (sizeof(unsigned long))
>  /* A future safe maximum remap size. */
>  #define VMW_PPN_PER_REMAP ((31 * 1024) / VMW_PPN_SIZE)
> +#define DMA_ADDR_INVALID ((dma_addr_t) 0)
> +#define DMA_PAGE_INVALID 0UL
>  
>  static int vmw_gmr2_bind(struct vmw_private *dev_priv,
> -			 struct page *pages[],
> +			 struct vmw_piter *iter,
>  			 unsigned long num_pages,
>  			 int gmr_id)
>  {
> @@ -81,11 +83,13 @@ static int vmw_gmr2_bind(struct vmw_private *dev_priv,
>  
>  		for (i = 0; i < nr; ++i) {
>  			if (VMW_PPN_SIZE <= 4)
> -				*cmd = page_to_pfn(*pages++);
> +				*cmd = vmw_piter_dma_addr(iter) >> PAGE_SHIFT;
>  			else
> -				*((uint64_t *)cmd) = page_to_pfn(*pages++);
> +				*((uint64_t *)cmd) = vmw_piter_dma_addr(iter) >>
> +					PAGE_SHIFT;
>  
>  			cmd += VMW_PPN_SIZE / sizeof(*cmd);
> +			vmw_piter_next(iter);
>  		}
>  
>  		num_pages -= nr;
> @@ -120,22 +124,54 @@ static void vmw_gmr2_unbind(struct vmw_private *dev_priv,
>  	vmw_fifo_commit(dev_priv, define_size);
>  }
>  
> +
> +static void vmw_gmr_free_descriptors(struct device *dev, dma_addr_t desc_dma,
> +				     struct list_head *desc_pages)
> +{
> +	struct page *page, *next;
> +	struct svga_guest_mem_descriptor *page_virtual;
> +	unsigned int desc_per_page = PAGE_SIZE /
> +		sizeof(struct svga_guest_mem_descriptor) - 1;
> +
> +	if (list_empty(desc_pages))
> +		return;
> +
> +	list_for_each_entry_safe(page, next, desc_pages, lru) {
> +		list_del_init(&page->lru);
> +
> +		if (likely(desc_dma != DMA_ADDR_INVALID)) {
> +			dma_unmap_page(dev, desc_dma, PAGE_SIZE,
> +				       DMA_TO_DEVICE);
> +		}
> +
> +		page_virtual = kmap_atomic(page);
> +		desc_dma = page_virtual[desc_per_page].ppn << PAGE_SHIFT;
> +		kunmap_atomic(page_virtual);
> +
> +		__free_page(page);
> +	}
> +}
> +
>  /**
>   * FIXME: Adjust to the ttm lowmem / highmem storage to minimize
>   * the number of used descriptors.
> + *
>   */
>  
> -static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
> -				     struct page *pages[],
> -				     unsigned long num_pages)
> +static int vmw_gmr_build_descriptors(struct device *dev,
> +				     struct list_head *desc_pages,
> +				     struct vmw_piter *iter,
> +				     unsigned long num_pages,
> +				     dma_addr_t *first_dma)
>  {
> -	struct page *page, *next;
> +	struct page *page;
>  	struct svga_guest_mem_descriptor *page_virtual = NULL;
>  	struct svga_guest_mem_descriptor *desc_virtual = NULL;
>  	unsigned int desc_per_page;
>  	unsigned long prev_pfn;
>  	unsigned long pfn;
>  	int ret;
> +	dma_addr_t desc_dma;
>  
>  	desc_per_page = PAGE_SIZE /
>  	    sizeof(struct svga_guest_mem_descriptor) - 1;
> @@ -148,23 +184,12 @@ static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
>  		}
>  
>  		list_add_tail(&page->lru, desc_pages);
> -
> -		/*
> -		 * Point previous page terminating descriptor to this
> -		 * page before unmapping it.
> -		 */
> -
> -		if (likely(page_virtual != NULL)) {
> -			desc_virtual->ppn = page_to_pfn(page);
> -			kunmap_atomic(page_virtual);
> -		}
> -
>  		page_virtual = kmap_atomic(page);
>  		desc_virtual = page_virtual - 1;
>  		prev_pfn = ~(0UL);
>  
>  		while (likely(num_pages != 0)) {
> -			pfn = page_to_pfn(*pages);
> +			pfn = vmw_piter_dma_addr(iter) >> PAGE_SHIFT;
>  
>  			if (pfn != prev_pfn + 1) {
>  
> @@ -181,104 +206,81 @@ static int vmw_gmr_build_descriptors(struct list_head *desc_pages,
>  			}
>  			prev_pfn = pfn;
>  			--num_pages;
> -			++pages;
> +			vmw_piter_next(iter);
>  		}
>  
> -		(++desc_virtual)->ppn = cpu_to_le32(0);
> +		(++desc_virtual)->ppn = DMA_PAGE_INVALID;
>  		desc_virtual->num_pages = cpu_to_le32(0);
> +		kunmap_atomic(page_virtual);
>  	}
>  
> -	if (likely(page_virtual != NULL))
> +	desc_dma = 0;
> +	list_for_each_entry_reverse(page, desc_pages, lru) {
> +		page_virtual = kmap_atomic(page);
> +		page_virtual[desc_per_page].ppn = desc_dma >> PAGE_SHIFT;
>  		kunmap_atomic(page_virtual);
> +		desc_dma = dma_map_page(dev, page, 0, PAGE_SIZE,
> +					DMA_TO_DEVICE);
> +
> +		if (unlikely(dma_mapping_error(dev, desc_dma)))
> +			goto out_err;
> +	}
> +	*first_dma = desc_dma;
>  
>  	return 0;
>  out_err:
> -	list_for_each_entry_safe(page, next, desc_pages, lru) {
> -		list_del_init(&page->lru);
> -		__free_page(page);
> -	}
> +	vmw_gmr_free_descriptors(dev, DMA_ADDR_INVALID, desc_pages);
>  	return ret;
>  }
>  
> -static inline void vmw_gmr_free_descriptors(struct list_head *desc_pages)
> -{
> -	struct page *page, *next;
> -
> -	list_for_each_entry_safe(page, next, desc_pages, lru) {
> -		list_del_init(&page->lru);
> -		__free_page(page);
> -	}
> -}
> -
>  static void vmw_gmr_fire_descriptors(struct vmw_private *dev_priv,
> -				     int gmr_id, struct list_head *desc_pages)
> +				     int gmr_id, dma_addr_t desc_dma)
>  {
> -	struct page *page;
> -
> -	if (unlikely(list_empty(desc_pages)))
> -		return;
> -
> -	page = list_entry(desc_pages->next, struct page, lru);
> -
>  	mutex_lock(&dev_priv->hw_mutex);
>  
>  	vmw_write(dev_priv, SVGA_REG_GMR_ID, gmr_id);
>  	wmb();
> -	vmw_write(dev_priv, SVGA_REG_GMR_DESCRIPTOR, page_to_pfn(page));
> +	vmw_write(dev_priv, SVGA_REG_GMR_DESCRIPTOR, desc_dma >> PAGE_SHIFT);
>  	mb();
>  
>  	mutex_unlock(&dev_priv->hw_mutex);
>  
>  }
>  
> -/**
> - * FIXME: Adjust to the ttm lowmem / highmem storage to minimize
> - * the number of used descriptors.
> - */
> -
> -static unsigned long vmw_gmr_count_descriptors(struct page *pages[],
> -					unsigned long num_pages)
> -{
> -	unsigned long prev_pfn = ~(0UL);
> -	unsigned long pfn;
> -	unsigned long descriptors = 0;
> -
> -	while (num_pages--) {
> -		pfn = page_to_pfn(*pages++);
> -		if (prev_pfn + 1 != pfn)
> -			++descriptors;
> -		prev_pfn = pfn;
> -	}
> -
> -	return descriptors;
> -}
> -
>  int vmw_gmr_bind(struct vmw_private *dev_priv,
> -		 struct page *pages[],
> +		 const struct vmw_sg_table *vsgt,
>  		 unsigned long num_pages,
>  		 int gmr_id)
>  {
>  	struct list_head desc_pages;
> +	dma_addr_t desc_dma = 0;
> +	struct device *dev = dev_priv->dev->dev;
> +	struct vmw_piter data_iter;
>  	int ret;
>  
> +	vmw_piter_start(&data_iter, vsgt, 0);
> +
> +	if (unlikely(!vmw_piter_next(&data_iter)))
> +		return 0;
> +
>  	if (likely(dev_priv->capabilities & SVGA_CAP_GMR2))
> -		return vmw_gmr2_bind(dev_priv, pages, num_pages, gmr_id);
> +		return vmw_gmr2_bind(dev_priv, &data_iter, num_pages, gmr_id);
>  
>  	if (unlikely(!(dev_priv->capabilities & SVGA_CAP_GMR)))
>  		return -EINVAL;
>  
> -	if (vmw_gmr_count_descriptors(pages, num_pages) >
> -	    dev_priv->max_gmr_descriptors)
> +	if (vsgt->num_regions > dev_priv->max_gmr_descriptors)
>  		return -EINVAL;
>  
>  	INIT_LIST_HEAD(&desc_pages);
>  
> -	ret = vmw_gmr_build_descriptors(&desc_pages, pages, num_pages);
> +	ret = vmw_gmr_build_descriptors(dev, &desc_pages, &data_iter,
> +					num_pages, &desc_dma);
>  	if (unlikely(ret != 0))
>  		return ret;
>  
> -	vmw_gmr_fire_descriptors(dev_priv, gmr_id, &desc_pages);
> -	vmw_gmr_free_descriptors(&desc_pages);
> +	vmw_gmr_fire_descriptors(dev_priv, gmr_id, desc_dma);
> +	vmw_gmr_free_descriptors(dev, desc_dma, &desc_pages);
>  
>  	return 0;
>  }
> -- 
> 1.7.10.4

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Re: [PATCH 2/2] drm/vmwgfx: Use the linux DMA api to get valid device addresses of pages

[Thomas Hellstrom]

On 11/04/2013 05:27 PM, Daniel Vetter wrote:
> On Mon, Nov 04, 2013 at 05:57:39AM -0800, Thomas Hellstrom wrote:
>> The code handles three different cases:
>> 1) physical page addresses. The ttm page array is used.
>> 2) DMA subsystem addresses. A scatter-gather list is used.
>> 3) Coherent pages. The ttm dma pool is used, together with the dma_ttm
>> array os dma_addr_t
>>
>> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
>> Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
> For i915.ko use we've added page iterators which should walk the physical
> backing storage.
>
> commit a321e91b6d73ed011ffceed384c40d2785cf723b
> Author: Imre Deak <imre.deak@intel.com>
> Date:   Wed Feb 27 17:02:56 2013 -0800
>
>      lib/scatterlist: add simple page iterator
>
>

Yes, I saw those iterators, (nice stuff!) and my patch are using them as 
a "base class", handling also
TTM page - and dma address arrays basically with the same interface. In 
the long run we might
want to move ttm over to sg_tables as well.

One problem, though, the page iterators break in the mapped case where
sg_dma_len(sg) != sg_len(sg).
An iommu implementation is allowed to reduce the sg list to a single 
segment, in which case those page
iterators will fall apart. I was planning to see if I could fix that up, 
but unfortunately there is no generic
dma_to_phys.
It all works now because intel_iommu, amd_iommu and swiotlb all keep the 
number of entries in an
sg list across mapping....

/Thomas

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Re: [PATCH 0/2] Make the vmwgfx driver reasonably DMA-API compliant

[Thomas Hellstrom]

On 11/04/2013 05:30 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Nov 04, 2013 at 05:57:37AM -0800, Thomas Hellstrom wrote:
>> These patches makes the vmwgfx driver use the DMA API to obtain valid
>> device addresses rather than blindly using physical addresses.
>>
>> The main motivation is to be able to use a virtual IOMMU in the future.
> Ooooh. Neat! Are there any RFC patches available?
>
Nope, not yet.

Thanks,
Thomas

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Re: [PATCH 1/2] drm/ttm: Enable the dma page pool also for intel IOMMUs

[Thomas Hellstrom]

On 11/04/2013 05:34 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Nov 04, 2013 at 05:57:38AM -0800, Thomas Hellstrom wrote:
>> Used by the vmwgfx driver
> That looks OK to me. And baremetal should not be
> affected as the Intel VT-d driver turns of the SWIOTLB
> driver - so it will still use the classic ttm pool code.
>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>
>
Thanks for reviewing, Konrad.

/Thomas

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Re: [PATCH 2/2] drm/vmwgfx: Use the linux DMA api to get valid device addresses of pages

[Thomas Hellstrom]

On 11/04/2013 05:40 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Nov 04, 2013 at 05:57:39AM -0800, Thomas Hellstrom wrote:
>> The code handles three different cases:
>> 1) physical page addresses. The ttm page array is used.
>> 2) DMA subsystem addresses. A scatter-gather list is used.
>> 3) Coherent pages. The ttm dma pool is used, together with the dma_ttm
>> array os dma_addr_t
>>
>> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
>> Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
> I looked at it from the TTM DMA perspective and it looks OK for me.
>
Great. Thanks,

Thomas

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