[10/24] drm/i915: Track GEN6 page table usage

Commit Message

Michel Thierry Dec. 18, 2014, 5:10 p.m. UTC

From: Ben Widawsky <[e-mail]>

Instead of implementing the full tracking + dynamic allocation, this
patch does a bit less than half of the work, by tracking and warning on
unexpected conditions. The tracking itself follows which PTEs within a
page table are currently being used for objects. The next patch will
modify this to actually allocate the page tables only when necessary.

With the current patch there isn't much in the way of making a gen
agnostic range allocation function. However, in the next patch we'll add
more specificity which makes having separate functions a bit easier to
manage.

One important change introduced here is that DMA mappings are
created/destroyed at the same page directories/tables are
allocated/deallocated.

Notice that aliasing PPGTT is not managed here. The patch which actually
begins dynamic allocation/teardown explains the reasoning for this.

v2: s/pdp.pagedir/pdp.pagedirs
Make a scratch page allocation helper

v3: Rebase and expand commit message.

Signed-off-by: Ben Widawsky <[e-mail]>
Signed-off-by: Michel Thierry <[e-mail]> (v3)
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 300 ++++++++++++++++++++++++++----------
 drivers/gpu/drm/i915/i915_gem_gtt.h | 151 +++++++++++++-----
 2 files changed, 333 insertions(+), 118 deletions(-)

Comments

Daniel Vetter Dec. 18, 2014, 9:06 p.m. UTC | #1

Ok this is just a very coarse high level comment. The only thing I really
looked for is very the dynamic pagetable allocation point happens and how
out-of-memory is handled in there.

But I've noticed that while trying to look for that that the patches and
code have a lot of history and often code comments and commit message
don't really agree with the code any more. I think that should be
carefully reviewed to make it less confusing.

On Thu, Dec 18, 2014 at 05:10:07PM +0000, Michel Thierry wrote:
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
> index c08fe8b..2eb6011 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.h
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
> @@ -54,7 +54,10 @@ typedef gen8_gtt_pte_t gen8_ppgtt_pde_t;
>  #define GEN6_PPGTT_PD_ENTRIES		512
>  #define GEN6_PD_SIZE			(GEN6_PPGTT_PD_ENTRIES * PAGE_SIZE)
>  #define GEN6_PD_ALIGN			(PAGE_SIZE * 16)
> +#define GEN6_PDE_SHIFT          22
>  #define GEN6_PDE_VALID			(1 << 0)
> +#define GEN6_PDE_MASK			(GEN6_PPGTT_PD_ENTRIES-1)
> +#define NUM_PTE(pde_shift)		(1 << (pde_shift - PAGE_SHIFT))
>  
>  #define GEN7_PTE_CACHE_L3_LLC		(3 << 1)
>  
> @@ -182,9 +185,33 @@ struct i915_vma {
>  	 * setting the valid PTE entries to a reserved scratch page. */
>  	void (*unbind_vma)(struct i915_vma *vma);
>  	/* Map an object into an address space with the given cache flags. */
> -	void (*bind_vma)(struct i915_vma *vma,
> -			 enum i915_cache_level cache_level,
> -			 u32 flags);
> +	int (*bind_vma)(struct i915_vma *vma,
> +			enum i915_cache_level cache_level,
> +			u32 flags);
> +};

So this patch changes the interface of vma->bind_vma to return errors when
the pagetable alloc fails. Afaics none of the callers get updated, and I
didn't see those adjustments in any other patch in this series. This
doesn't work (or I'm blind).

Also I'm not too happy with smashing this into ->bind_vma: This function
is also called in places where we know that the pagetables must be there
already, namely when changing pte bits in i915_gem_object_set_cache_level.

Imo we should add an explicit call to allocate required pagetables in
i915_gem_object_bind_to_vm, which is the only place which actually needs
this (I think).
-Daniel

Patch

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 564770f..faa0603 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -138,10 +138,9 @@  static int sanitize_enable_ppgtt(struct drm_device *dev, int enable_ppgtt)
 		return has_aliasing_ppgtt ? 1 : 0;
 }
 
-
-static void ppgtt_bind_vma(struct i915_vma *vma,
-			   enum i915_cache_level cache_level,
-			   u32 flags);
+static int ppgtt_bind_vma(struct i915_vma *vma,
+			  enum i915_cache_level cache_level,
+			  u32 flags);
 static void ppgtt_unbind_vma(struct i915_vma *vma);
 
 static inline gen8_gtt_pte_t gen8_pte_encode(dma_addr_t addr,
@@ -275,27 +274,99 @@  static gen6_gtt_pte_t iris_pte_encode(dma_addr_t addr,
 	return pte;
 }
 
-static void free_pt_single(struct i915_pagetab *pt)
-{
+#define i915_dma_unmap_single(px, dev) do { \
+	pci_unmap_page((dev)->pdev, (px)->daddr, 4096, PCI_DMA_BIDIRECTIONAL); \
+} while (0);
+
+/**
+ * i915_dma_map_px_single() - Create a dma mapping for a page table/dir/etc.
+ * @px:		Page table/dir/etc to get a DMA map for
+ * @dev:	drm device
+ *
+ * Page table allocations are unified across all gens. They always require a
+ * single 4k allocation, as well as a DMA mapping. If we keep the structs
+ * symmetric here, the simple macro covers us for every page table type.
+ *
+ * Return: 0 if success.
+ */
+#define i915_dma_map_px_single(px, dev) \
+	pci_dma_mapping_error((dev)->pdev, \
+			      (px)->daddr = pci_map_page((dev)->pdev, \
+							 (px)->page, 0, 4096, \
+							 PCI_DMA_BIDIRECTIONAL))
+
+static void __free_pt_single(struct i915_pagetab *pt, struct drm_device *dev,
+			     int scratch)
+{
+	if (WARN(scratch ^ pt->scratch,
+		 "Tried to free scratch = %d. Is scratch = %d\n",
+		 scratch, pt->scratch))
+		return;
+
 	if (WARN_ON(!pt->page))
 		return;
+
+	if (!scratch) {
+		const size_t count = INTEL_INFO(dev)->gen >= 8 ?
+			GEN8_PTES_PER_PAGE : I915_PPGTT_PT_ENTRIES;
+		WARN(!bitmap_empty(pt->used_ptes, count),
+		     "Free page table with %d used pages\n",
+		     bitmap_weight(pt->used_ptes, count));
+	}
+
+	i915_dma_unmap_single(pt, dev);
 	__free_page(pt->page);
+	kfree(pt->used_ptes);
 	kfree(pt);
 }
 
-static struct i915_pagetab *alloc_pt_single(void)
+#define free_pt_single(pt, dev) \
+	__free_pt_single(pt, dev, false)
+#define free_pt_scratch(pt, dev) \
+	__free_pt_single(pt, dev, true)
+
+static struct i915_pagetab *alloc_pt_single(struct drm_device *dev)
 {
 	struct i915_pagetab *pt;
+	const size_t count = INTEL_INFO(dev)->gen >= 8 ?
+		GEN8_PTES_PER_PAGE : I915_PPGTT_PT_ENTRIES;
+	int ret = -ENOMEM;
 
 	pt = kzalloc(sizeof(*pt), GFP_KERNEL);
 	if (!pt)
 		return ERR_PTR(-ENOMEM);
 
+	pt->used_ptes = kcalloc(BITS_TO_LONGS(count), sizeof(*pt->used_ptes),
+				GFP_KERNEL);
+
+	if (!pt->used_ptes)
+		goto fail_bitmap;
+
 	pt->page = alloc_page(GFP_KERNEL | __GFP_ZERO);
-	if (!pt->page) {
-		kfree(pt);
-		return ERR_PTR(-ENOMEM);
-	}
+	if (!pt->page)
+		goto fail_page;
+
+	ret = i915_dma_map_px_single(pt, dev);
+	if (ret)
+		goto fail_dma;
+
+	return pt;
+
+fail_dma:
+	__free_page(pt->page);
+fail_page:
+	kfree(pt->used_ptes);
+fail_bitmap:
+	kfree(pt);
+
+	return ERR_PTR(ret);
+}
+
+static inline struct i915_pagetab *alloc_pt_scratch(struct drm_device *dev)
+{
+	struct i915_pagetab *pt = alloc_pt_single(dev);
+	if (!IS_ERR(pt))
+		pt->scratch = 1;
 
 	return pt;
 }
@@ -313,7 +384,9 @@  static struct i915_pagetab *alloc_pt_single(void)
  *
  * Return: 0 if allocation succeeded.
  */
-static int alloc_pt_range(struct i915_pagedir *pd, uint16_t pde, size_t count)
+static int alloc_pt_range(struct i915_pagedir *pd, uint16_t pde, size_t count,
+		  struct drm_device *dev)
+
 {
 	int i, ret;
 
@@ -323,7 +396,7 @@  static int alloc_pt_range(struct i915_pagedir *pd, uint16_t pde, size_t count)
 	BUG_ON(pde + count > GEN6_PPGTT_PD_ENTRIES);
 
 	for (i = pde; i < pde + count; i++) {
-		struct i915_pagetab *pt = alloc_pt_single();
+		struct i915_pagetab *pt = alloc_pt_single(dev);
 		if (IS_ERR(pt)) {
 			ret = PTR_ERR(pt);
 			goto err_out;
@@ -338,7 +411,7 @@  static int alloc_pt_range(struct i915_pagedir *pd, uint16_t pde, size_t count)
 
 err_out:
 	while (i--)
-		free_pt_single(pd->page_tables[i]);
+		free_pt_single(pd->page_tables[i], dev);
 	return ret;
 }
 
@@ -506,7 +579,7 @@  static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
 	}
 }
 
-static void gen8_free_page_tables(struct i915_pagedir *pd)
+static void gen8_free_page_tables(struct i915_pagedir *pd, struct drm_device *dev)
 {
 	int i;
 
@@ -514,7 +587,7 @@  static void gen8_free_page_tables(struct i915_pagedir *pd)
 		return;
 
 	for (i = 0; i < GEN8_PDES_PER_PAGE; i++) {
-		free_pt_single(pd->page_tables[i]);
+		free_pt_single(pd->page_tables[i], dev);
 		pd->page_tables[i] = NULL;
 	}
 }
@@ -524,7 +597,7 @@  static void gen8_ppgtt_free(struct i915_hw_ppgtt *ppgtt)
 	int i;
 
 	for (i = 0; i < ppgtt->num_pd_pages; i++) {
-		gen8_free_page_tables(ppgtt->pdp.pagedir[i]);
+		gen8_free_page_tables(ppgtt->pdp.pagedir[i], ppgtt->base.dev);
 		free_pd_single(ppgtt->pdp.pagedir[i]);
 	}
 }
@@ -569,7 +642,7 @@  static int gen8_ppgtt_allocate_page_tables(struct i915_hw_ppgtt *ppgtt)
 
 	for (i = 0; i < ppgtt->num_pd_pages; i++) {
 		ret = alloc_pt_range(ppgtt->pdp.pagedir[i],
-				     0, GEN8_PDES_PER_PAGE);
+				     0, GEN8_PDES_PER_PAGE, ppgtt->base.dev);
 		if (ret)
 			goto unwind_out;
 	}
@@ -578,7 +651,7 @@  static int gen8_ppgtt_allocate_page_tables(struct i915_hw_ppgtt *ppgtt)
 
 unwind_out:
 	while (i--)
-		gen8_free_page_tables(ppgtt->pdp.pagedir[i]);
+		gen8_free_page_tables(ppgtt->pdp.pagedir[i], ppgtt->base.dev);
 
 	return -ENOMEM;
 }
@@ -808,26 +881,36 @@  static void gen6_dump_ppgtt(struct i915_hw_ppgtt *ppgtt, struct seq_file *m)
 	}
 }
 
-static void gen6_write_pdes(struct i915_hw_ppgtt *ppgtt)
+/* Write pde (index) from the page directory @pd to the page table @pt */
+static void gen6_write_pdes(struct i915_pagedir *pd,
+			    const int pde, struct i915_pagetab *pt)
 {
-	struct drm_i915_private *dev_priv = ppgtt->base.dev->dev_private;
-	gen6_gtt_pte_t __iomem *pd_addr;
-	uint32_t pd_entry;
-	int i;
+	struct i915_hw_ppgtt *ppgtt =
+		container_of(pd, struct i915_hw_ppgtt, pd);
+	u32 pd_entry;
 
-	WARN_ON(ppgtt->pd.pd_offset & 0x3f);
-	pd_addr = (gen6_gtt_pte_t __iomem*)dev_priv->gtt.gsm +
-		ppgtt->pd.pd_offset / sizeof(gen6_gtt_pte_t);
-	for (i = 0; i < ppgtt->num_pd_entries; i++) {
-		dma_addr_t pt_addr;
+	pd_entry = GEN6_PDE_ADDR_ENCODE(pt->daddr);
+	pd_entry |= GEN6_PDE_VALID;
 
-		pt_addr = ppgtt->pd.page_tables[i]->daddr;
-		pd_entry = GEN6_PDE_ADDR_ENCODE(pt_addr);
-		pd_entry |= GEN6_PDE_VALID;
+	writel(pd_entry, ppgtt->pd_addr + pde);
 
-		writel(pd_entry, pd_addr + i);
-	}
-	readl(pd_addr);
+	/* XXX: Caller needs to make sure the write completes if necessary */
+}
+
+/* Write all the page tables found in the ppgtt structure to incrementing page
+ * directories. */
+static void gen6_write_page_range(struct drm_i915_private *dev_priv,
+				struct i915_pagedir *pd, uint32_t start, uint32_t length)
+{
+	struct i915_pagetab *pt;
+	uint32_t pde, temp;
+
+	gen6_for_each_pde(pt, pd, start, length, temp, pde)
+		gen6_write_pdes(pd, pde, pt);
+
+	/* Make sure write is complete before other code can use this page
+	 * table. Also require for WC mapped PTEs */
+	readl(dev_priv->gtt.gsm);
 }
 
 static uint32_t get_pd_offset(struct i915_hw_ppgtt *ppgtt)
@@ -1043,13 +1126,59 @@  static void gen6_ppgtt_unmap_pages(struct i915_hw_ppgtt *ppgtt)
 			       4096, PCI_DMA_BIDIRECTIONAL);
 }
 
+static int gen6_alloc_va_range(struct i915_address_space *vm,
+			       uint64_t start, uint64_t length)
+{
+	struct i915_hw_ppgtt *ppgtt =
+				container_of(vm, struct i915_hw_ppgtt, base);
+	struct i915_pagetab *pt;
+	uint32_t pde, temp;
+
+	gen6_for_each_pde(pt, &ppgtt->pd, start, length, temp, pde) {
+		int j;
+
+		DECLARE_BITMAP(tmp_bitmap, I915_PPGTT_PT_ENTRIES);
+		bitmap_zero(tmp_bitmap, I915_PPGTT_PT_ENTRIES);
+		bitmap_set(tmp_bitmap, gen6_pte_index(start),
+			   gen6_pte_count(start, length));
+
+		/* TODO: To be done in the next patch. Map the page/insert
+		 * entries here */
+		for_each_set_bit(j, tmp_bitmap, I915_PPGTT_PT_ENTRIES) {
+			if (test_bit(j, pt->used_ptes)) {
+				/* Check that we're changing cache levels */
+			}
+		}
+
+		bitmap_or(pt->used_ptes, pt->used_ptes, tmp_bitmap,
+				I915_PPGTT_PT_ENTRIES);
+	}
+
+	return 0;
+}
+
+static void gen6_teardown_va_range(struct i915_address_space *vm,
+				   uint64_t start, uint64_t length)
+{
+	struct i915_hw_ppgtt *ppgtt =
+				container_of(vm, struct i915_hw_ppgtt, base);
+	struct i915_pagetab *pt;
+	uint32_t pde, temp;
+
+	gen6_for_each_pde(pt, &ppgtt->pd, start, length, temp, pde) {
+		bitmap_clear(pt->used_ptes, gen6_pte_index(start),
+			     gen6_pte_count(start, length));
+	}
+}
+
 static void gen6_ppgtt_free(struct i915_hw_ppgtt *ppgtt)
 {
 	int i;
 
 	for (i = 0; i < ppgtt->num_pd_entries; i++)
-		free_pt_single(ppgtt->pd.page_tables[i]);
+		free_pt_single(ppgtt->pd.page_tables[i], ppgtt->base.dev);
 
+	free_pt_scratch(ppgtt->scratch_pt, ppgtt->base.dev);
 	free_pd_single(&ppgtt->pd);
 }
 
@@ -1076,6 +1205,9 @@  static int gen6_ppgtt_allocate_page_directories(struct i915_hw_ppgtt *ppgtt)
 	 * size. We allocate at the top of the GTT to avoid fragmentation.
 	 */
 	BUG_ON(!drm_mm_initialized(&dev_priv->gtt.base.mm));
+	ppgtt->scratch_pt = alloc_pt_scratch(ppgtt->base.dev);
+	if (IS_ERR(ppgtt->scratch_pt))
+		return PTR_ERR(ppgtt->scratch_pt);
 alloc:
 	ret = drm_mm_insert_node_in_range_generic(&dev_priv->gtt.base.mm,
 						  &ppgtt->node, GEN6_PD_SIZE,
@@ -1089,20 +1221,25 @@  alloc:
 					       0, dev_priv->gtt.base.total,
 					       0);
 		if (ret)
-			return ret;
+			goto err_out;
 
 		retried = true;
 		goto alloc;
 	}
 
 	if (ret)
-		return ret;
+		goto err_out;
+
 
 	if (ppgtt->node.start < dev_priv->gtt.mappable_end)
 		DRM_DEBUG("Forced to use aperture for PDEs\n");
 
 	ppgtt->num_pd_entries = GEN6_PPGTT_PD_ENTRIES;
 	return 0;
+
+err_out:
+	free_pt_scratch(ppgtt->scratch_pt, ppgtt->base.dev);
+	return ret;
 }
 
 static int gen6_ppgtt_alloc(struct i915_hw_ppgtt *ppgtt)
@@ -1113,7 +1250,9 @@  static int gen6_ppgtt_alloc(struct i915_hw_ppgtt *ppgtt)
 	if (ret)
 		return ret;
 
-	ret = alloc_pt_range(&ppgtt->pd, 0, ppgtt->num_pd_entries);
+	ret = alloc_pt_range(&ppgtt->pd, 0, ppgtt->num_pd_entries,
+			ppgtt->base.dev);
+
 	if (ret) {
 		drm_mm_remove_node(&ppgtt->node);
 		return ret;
@@ -1122,30 +1261,6 @@  static int gen6_ppgtt_alloc(struct i915_hw_ppgtt *ppgtt)
 	return 0;
 }
 
-static int gen6_ppgtt_setup_page_tables(struct i915_hw_ppgtt *ppgtt)
-{
-	struct drm_device *dev = ppgtt->base.dev;
-	int i;
-
-	for (i = 0; i < ppgtt->num_pd_entries; i++) {
-		struct page *page;
-		dma_addr_t pt_addr;
-
-		page = ppgtt->pd.page_tables[i]->page;
-		pt_addr = pci_map_page(dev->pdev, page, 0, 4096,
-				       PCI_DMA_BIDIRECTIONAL);
-
-		if (pci_dma_mapping_error(dev->pdev, pt_addr)) {
-			gen6_ppgtt_unmap_pages(ppgtt);
-			return -EIO;
-		}
-
-		ppgtt->pd.page_tables[i]->daddr = pt_addr;
-	}
-
-	return 0;
-}
-
 static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
 {
 	struct drm_device *dev = ppgtt->base.dev;
@@ -1166,12 +1281,8 @@  static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
 	if (ret)
 		return ret;
 
-	ret = gen6_ppgtt_setup_page_tables(ppgtt);
-	if (ret) {
-		gen6_ppgtt_free(ppgtt);
-		return ret;
-	}
-
+	ppgtt->base.allocate_va_range = gen6_alloc_va_range;
+	ppgtt->base.teardown_va_range = gen6_teardown_va_range;
 	ppgtt->base.clear_range = gen6_ppgtt_clear_range;
 	ppgtt->base.insert_entries = gen6_ppgtt_insert_entries;
 	ppgtt->base.cleanup = gen6_ppgtt_cleanup;
@@ -1182,11 +1293,15 @@  static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
 	ppgtt->pd.pd_offset =
 		ppgtt->node.start / PAGE_SIZE * sizeof(gen6_gtt_pte_t);
 
+	ppgtt->pd_addr = (gen6_gtt_pte_t __iomem *)dev_priv->gtt.gsm +
+		ppgtt->pd.pd_offset / sizeof(gen6_gtt_pte_t);
+
+	gen6_write_page_range(dev_priv, &ppgtt->pd, 0, ppgtt->base.total);
+
 	DRM_DEBUG_DRIVER("Allocated pde space (%ldM) at GTT entry: %lx\n",
 			 ppgtt->node.size >> 20,
 			 ppgtt->node.start / PAGE_SIZE);
 
-	gen6_write_pdes(ppgtt);
 	DRM_DEBUG("Adding PPGTT at offset %x\n",
 		  ppgtt->pd.pd_offset << 10);
 
@@ -1301,17 +1416,28 @@  void  i915_ppgtt_release(struct kref *kref)
 	kfree(ppgtt);
 }
 
-static void
+static int
 ppgtt_bind_vma(struct i915_vma *vma,
 	       enum i915_cache_level cache_level,
 	       u32 flags)
 {
+	int ret;
+
 	/* Currently applicable only to VLV */
 	if (vma->obj->gt_ro)
 		flags |= PTE_READ_ONLY;
 
+	if (vma->vm->allocate_va_range) {
+		ret = vma->vm->allocate_va_range(vma->vm,
+						 vma->node.start,
+						 vma->node.size);
+		if (ret)
+			return ret;
+	}
+
 	vma->vm->insert_entries(vma->vm, vma->obj->pages, vma->node.start,
 				cache_level, flags);
+	return 0;
 }
 
 static void ppgtt_unbind_vma(struct i915_vma *vma)
@@ -1320,6 +1446,9 @@  static void ppgtt_unbind_vma(struct i915_vma *vma)
 			     vma->node.start,
 			     vma->obj->base.size,
 			     true);
+	if (vma->vm->teardown_va_range)
+		vma->vm->teardown_va_range(vma->vm,
+					   vma->node.start, vma->node.size);
 }
 
 extern int intel_iommu_gfx_mapped;
@@ -1463,13 +1592,14 @@  void i915_gem_restore_gtt_mappings(struct drm_device *dev)
 
 	list_for_each_entry(vm, &dev_priv->vm_list, global_link) {
 		/* TODO: Perhaps it shouldn't be gen6 specific */
-		if (i915_is_ggtt(vm)) {
-			if (dev_priv->mm.aliasing_ppgtt)
-				gen6_write_pdes(dev_priv->mm.aliasing_ppgtt);
-			continue;
-		}
 
-		gen6_write_pdes(container_of(vm, struct i915_hw_ppgtt, base));
+		struct i915_hw_ppgtt *ppgtt =
+			container_of(vm, struct i915_hw_ppgtt, base);
+
+		if (i915_is_ggtt(vm))
+			ppgtt = dev_priv->mm.aliasing_ppgtt;
+
+		gen6_write_page_range(dev_priv, &ppgtt->pd, 0, ppgtt->num_pd_entries);
 	}
 
 	i915_ggtt_flush(dev_priv);
@@ -1634,9 +1764,9 @@  static void gen6_ggtt_clear_range(struct i915_address_space *vm,
 }
 
 
-static void i915_ggtt_bind_vma(struct i915_vma *vma,
-			       enum i915_cache_level cache_level,
-			       u32 unused)
+static int i915_ggtt_bind_vma(struct i915_vma *vma,
+			      enum i915_cache_level cache_level,
+			      u32 unused)
 {
 	const unsigned long entry = vma->node.start >> PAGE_SHIFT;
 	unsigned int flags = (cache_level == I915_CACHE_NONE) ?
@@ -1645,6 +1775,8 @@  static void i915_ggtt_bind_vma(struct i915_vma *vma,
 	BUG_ON(!i915_is_ggtt(vma->vm));
 	intel_gtt_insert_sg_entries(vma->ggtt_view.pages, entry, flags);
 	vma->bound = GLOBAL_BIND;
+
+	return 0;
 }
 
 static void i915_ggtt_clear_range(struct i915_address_space *vm,
@@ -1667,9 +1799,9 @@  static void i915_ggtt_unbind_vma(struct i915_vma *vma)
 	intel_gtt_clear_range(first, size);
 }
 
-static void ggtt_bind_vma(struct i915_vma *vma,
-			  enum i915_cache_level cache_level,
-			  u32 flags)
+static int ggtt_bind_vma(struct i915_vma *vma,
+			 enum i915_cache_level cache_level,
+			 u32 flags)
 {
 	struct drm_device *dev = vma->vm->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -1710,6 +1842,8 @@  static void ggtt_bind_vma(struct i915_vma *vma,
 					    cache_level, flags);
 		vma->bound |= LOCAL_BIND;
 	}
+
+	return 0;
 }
 
 static void ggtt_unbind_vma(struct i915_vma *vma)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index c08fe8b..2eb6011 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -54,7 +54,10 @@  typedef gen8_gtt_pte_t gen8_ppgtt_pde_t;
 #define GEN6_PPGTT_PD_ENTRIES		512
 #define GEN6_PD_SIZE			(GEN6_PPGTT_PD_ENTRIES * PAGE_SIZE)
 #define GEN6_PD_ALIGN			(PAGE_SIZE * 16)
+#define GEN6_PDE_SHIFT          22
 #define GEN6_PDE_VALID			(1 << 0)
+#define GEN6_PDE_MASK			(GEN6_PPGTT_PD_ENTRIES-1)
+#define NUM_PTE(pde_shift)		(1 << (pde_shift - PAGE_SHIFT))
 
 #define GEN7_PTE_CACHE_L3_LLC		(3 << 1)
 
@@ -182,9 +185,33 @@  struct i915_vma {
 	 * setting the valid PTE entries to a reserved scratch page. */
 	void (*unbind_vma)(struct i915_vma *vma);
 	/* Map an object into an address space with the given cache flags. */
-	void (*bind_vma)(struct i915_vma *vma,
-			 enum i915_cache_level cache_level,
-			 u32 flags);
+	int (*bind_vma)(struct i915_vma *vma,
+			enum i915_cache_level cache_level,
+			u32 flags);
+};
+
+
+struct i915_pagetab {
+	struct page *page;
+	dma_addr_t daddr;
+
+	unsigned long *used_ptes;
+	unsigned int scratch:1;
+};
+
+struct i915_pagedir {
+	struct page *page; /* NULL for GEN6-GEN7 */
+	union {
+		uint32_t pd_offset;
+		dma_addr_t daddr;
+	};
+
+	struct i915_pagetab *page_tables[GEN6_PPGTT_PD_ENTRIES];
+};
+
+struct i915_pagedirpo {
+	/* struct page *page; */
+	struct i915_pagedir *pagedir[GEN8_LEGACY_PDPES];
 };
 
 struct i915_address_space {
@@ -226,6 +253,12 @@  struct i915_address_space {
 	gen6_gtt_pte_t (*pte_encode)(dma_addr_t addr,
 				     enum i915_cache_level level,
 				     bool valid, u32 flags); /* Create a valid PTE */
+	int (*allocate_va_range)(struct i915_address_space *vm,
+				 uint64_t start,
+				 uint64_t length);
+	void (*teardown_va_range)(struct i915_address_space *vm,
+				  uint64_t start,
+				  uint64_t length);
 	void (*clear_range)(struct i915_address_space *vm,
 			    uint64_t start,
 			    uint64_t length,
@@ -237,6 +270,29 @@  struct i915_address_space {
 	void (*cleanup)(struct i915_address_space *vm);
 };
 
+struct i915_hw_ppgtt {
+	struct i915_address_space base;
+	struct kref ref;
+	struct drm_mm_node node;
+	unsigned num_pd_entries;
+	unsigned num_pd_pages; /* gen8+ */
+	union {
+		struct i915_pagedirpo pdp;
+		struct i915_pagedir pd;
+	};
+
+	struct i915_pagetab *scratch_pt;
+
+	struct drm_i915_file_private *file_priv;
+
+	gen6_gtt_pte_t __iomem *pd_addr;
+
+	int (*enable)(struct i915_hw_ppgtt *ppgtt);
+	int (*switch_mm)(struct i915_hw_ppgtt *ppgtt,
+			 struct intel_engine_cs *ring);
+	void (*debug_dump)(struct i915_hw_ppgtt *ppgtt, struct seq_file *m);
+};
+
 /* The Graphics Translation Table is the way in which GEN hardware translates a
  * Graphics Virtual Address into a Physical Address. In addition to the normal
  * collateral associated with any va->pa translations GEN hardware also has a
@@ -265,44 +321,69 @@  struct i915_gtt {
 			  unsigned long *mappable_end);
 };
 
-struct i915_pagetab {
-	struct page *page;
-	dma_addr_t daddr;
-};
+/* For each pde iterates over every pde between from start until start + length.
+ * If start, and start+length are not perfectly divisible, the macro will round
+ * down, and up as needed. The macro modifies pde, start, and length. Dev is
+ * only used to differentiate shift values. Temp is temp.  On gen6/7, start = 0,
+ * and length = 2G effectively iterates over every PDE in the system. On gen8+
+ * it simply iterates over every page directory entry in a page directory.
+ *
+ * XXX: temp is not actually needed, but it saves doing the ALIGN operation.
+ */
+#define gen6_for_each_pde(pt, pd, start, length, temp, iter) \
+	for (iter = gen6_pde_index(start), pt = (pd)->page_tables[iter]; \
+	     length > 0 && iter < GEN6_PPGTT_PD_ENTRIES; \
+	     pt = (pd)->page_tables[++iter], \
+	     temp = ALIGN(start+1, 1 << GEN6_PDE_SHIFT) - start, \
+	     temp = min(temp, (unsigned)length), \
+	     start += temp, length -= temp)
+
+static inline uint32_t i915_pte_index(uint64_t address, uint32_t pde_shift)
+{
+	const uint32_t mask = NUM_PTE(pde_shift) - 1;
+	return (address >> PAGE_SHIFT) & mask;
+}
 
-struct i915_pagedir {
-	struct page *page; /* NULL for GEN6-GEN7 */
-	union {
-		uint32_t pd_offset;
-		dma_addr_t daddr;
-	};
+/* Helper to counts the number of PTEs within the given length. This count does
+* not cross a page table boundary, so the max value would be
+* I915_PPGTT_PT_ENTRIES for GEN6, and GEN8_PTES_PER_PAGE for GEN8.
+*/
+static inline size_t i915_pte_count(uint64_t addr, size_t length,
+					uint32_t pde_shift)
+{
+	const uint64_t mask = ~((1 << pde_shift) - 1);
+	uint64_t end;
 
-	struct i915_pagetab *page_tables[GEN6_PPGTT_PD_ENTRIES]; /* PDEs */
-};
+	BUG_ON(length == 0);
+	BUG_ON(offset_in_page(addr|length));
 
-struct i915_pagedirpo {
-	/* struct page *page; */
-	struct i915_pagedir *pagedir[GEN8_LEGACY_PDPES];
-};
+	end = addr + length;
 
-struct i915_hw_ppgtt {
-	struct i915_address_space base;
-	struct kref ref;
-	struct drm_mm_node node;
-	unsigned num_pd_entries;
-	unsigned num_pd_pages; /* gen8+ */
-	union {
-		struct i915_pagedirpo pdp;
-		struct i915_pagedir pd;
-	};
+	if ((addr & mask) != (end & mask))
+		return NUM_PTE(pde_shift) - i915_pte_index(addr, pde_shift);
 
-	struct drm_i915_file_private *file_priv;
+	return i915_pte_index(end, pde_shift) - i915_pte_index(addr, pde_shift);
+}
 
-	int (*enable)(struct i915_hw_ppgtt *ppgtt);
-	int (*switch_mm)(struct i915_hw_ppgtt *ppgtt,
-			 struct intel_engine_cs *ring);
-	void (*debug_dump)(struct i915_hw_ppgtt *ppgtt, struct seq_file *m);
-};
+static inline uint32_t i915_pde_index(uint64_t addr, uint32_t shift)
+{
+	return (addr >> shift) & GEN6_PDE_MASK;
+}
+
+static inline uint32_t gen6_pte_index(uint32_t addr)
+{
+	return i915_pte_index(addr, GEN6_PDE_SHIFT);
+}
+
+static inline size_t gen6_pte_count(uint32_t addr, uint32_t length)
+{
+	return i915_pte_count(addr, length, GEN6_PDE_SHIFT);
+}
+
+static inline uint32_t gen6_pde_index(uint32_t addr)
+{
+	return i915_pde_index(addr, GEN6_PDE_SHIFT);
+}
 
 int i915_gem_gtt_init(struct drm_device *dev);
 void i915_gem_init_global_gtt(struct drm_device *dev);