diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 6703721..117b88a 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -536,7 +536,7 @@ static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
 	}
 }
 
-static void __gen8_do_map_pt(gen8_ppgtt_pde_t *pde,
+static void __gen8_do_map_pt(gen8_ppgtt_pde_t * const pde,
 			     struct i915_pagetab *pt,
 			     struct drm_device *dev)
 {
@@ -553,7 +553,7 @@ static void gen8_map_pagetable_range(struct i915_pagedir *pd,
 				     uint64_t length,
 				     struct drm_device *dev)
 {
-	gen8_ppgtt_pde_t *pagedir = kmap_atomic(pd->page);
+	gen8_ppgtt_pde_t * const pagedir = kmap_atomic(pd->page);
 	struct i915_pagetab *pt;
 	uint64_t temp, pde;
 
@@ -566,8 +566,9 @@ static void gen8_map_pagetable_range(struct i915_pagedir *pd,
 	kunmap_atomic(pagedir);
 }
 
-static void gen8_teardown_va_range(struct i915_address_space *vm,
-				   uint64_t start, uint64_t length)
+static void __gen8_teardown_va_range(struct i915_address_space *vm,
+				     uint64_t start, uint64_t length,
+				     bool dead)
 {
 	struct i915_hw_ppgtt *ppgtt =
 		        container_of(vm, struct i915_hw_ppgtt, base);
@@ -589,6 +590,13 @@ static void gen8_teardown_va_range(struct i915_address_space *vm,
 			     pdpe, vm);
 			continue;
 		} else {
+			if (dead && pd->zombie) {
+				WARN_ON(test_bit(pdpe, ppgtt->pdp.used_pdpes));
+				free_pd_single(pd, vm->dev);
+				ppgtt->pdp.pagedirs[pdpe] = NULL;
+				continue;
+			}
+
 			WARN(!test_bit(pdpe, ppgtt->pdp.used_pdpes),
 			     "PDPE %d not reserved, but is allocated (%p)",
 			     pdpe, vm);
@@ -600,34 +608,65 @@ static void gen8_teardown_va_range(struct i915_address_space *vm,
 				     "PDE %d is not allocated, but is reserved (%p)\n",
 				     pde, vm);
 				continue;
-			} else
+			} else {
+				if (dead && pt->zombie) {
+					WARN_ON(test_bit(pde, pd->used_pdes));
+					free_pt_single(pt, vm->dev);
+					pd->page_tables[pde] = NULL;
+					continue;
+				}
 				WARN(!test_bit(pde, pd->used_pdes),
 				     "PDE %d not reserved, but is allocated (%p)",
 				     pde, vm);
+			}
 
 			bitmap_clear(pt->used_ptes,
 				     gen8_pte_index(pd_start),
 				     gen8_pte_count(pd_start, pd_len));
 
+
 			if (bitmap_empty(pt->used_ptes, GEN8_PTES_PER_PT)) {
+				WARN_ON(!test_and_clear_bit(pde, pd->used_pdes));
+				if (!dead) {
+					pt->zombie = 1;
+					continue;
+				}
 				free_pt_single(pt, vm->dev);
 				pd->page_tables[pde] = NULL;
-				WARN_ON(!test_and_clear_bit(pde, pd->used_pdes));
+
 			}
 		}
 
+		gen8_ppgtt_clear_range(vm, pd_start, pd_len, true);
+
 		if (bitmap_empty(pd->used_pdes, I915_PDES_PER_PD)) {
+			WARN_ON(!test_and_clear_bit(pdpe, ppgtt->pdp.used_pdpes));
+			if (!dead) {
+				/* We've unmapped a possibly live context. Make
+				 * note of it so we can clean it up later. */
+				pd->zombie = 1;
+				continue;
+			}
 			free_pd_single(pd, vm->dev);
 			ppgtt->pdp.pagedirs[pdpe] = NULL;
-			WARN_ON(!test_and_clear_bit(pdpe, ppgtt->pdp.used_pdpes));
 		}
 	}
 }
 
+static void gen8_teardown_va_range(struct i915_address_space *vm,
+				   uint64_t start, uint64_t length)
+{
+	__gen8_teardown_va_range(vm, start, length, false);
+}
+
 static void gen8_ppgtt_free(struct i915_hw_ppgtt *ppgtt)
 {
-	gen8_teardown_va_range(&ppgtt->base,
-			       ppgtt->base.start, ppgtt->base.total);
+	trace_i915_va_teardown(&ppgtt->base,
+			       ppgtt->base.start, ppgtt->base.total,
+			       VM_TO_TRACE_NAME(&ppgtt->base));
+	__gen8_teardown_va_range(&ppgtt->base,
+				 ppgtt->base.start, ppgtt->base.total,
+				 true);
 }
 
 static void gen8_ppgtt_cleanup(struct i915_address_space *vm)
@@ -638,58 +677,167 @@ static void gen8_ppgtt_cleanup(struct i915_address_space *vm)
 	gen8_ppgtt_free(ppgtt);
 }
 
-static int gen8_ppgtt_alloc_pagetabs(struct i915_pagedir *pd,
+/**
+ * gen8_ppgtt_alloc_pagetabs() - Allocate page tables for VA range.
+ * @ppgtt:	Master ppgtt structure.
+ * @pd:		Page directory for this address range.
+ * @start:	Starting virtual address to begin allocations.
+ * @length	Size of the allocations.
+ * @new_pts:	Bitmap set by function with new allocations. Likely used by the
+ *		caller to free on error.
+ *
+ * Allocate the required number of page tables. Extremely similar to
+ * gen8_ppgtt_alloc_pagedirs(). The main difference is here we are limited by
+ * the page directory boundary (instead of the page directory pointer). That
+ * boundary is 1GB virtual. Therefore, unlike gen8_ppgtt_alloc_pagedirs(), it is
+ * possible, and likely that the caller will need to use multiple calls of this
+ * function to achieve the appropriate allocation.
+ *
+ * Return: 0 if success; negative error code otherwise.
+ */
+static int gen8_ppgtt_alloc_pagetabs(struct i915_hw_ppgtt *ppgtt,
+				     struct i915_pagedir *pd,
 				     uint64_t start,
 				     uint64_t length,
-				     struct drm_device *dev)
+				     unsigned long *new_pts)
 {
-	struct i915_pagetab *unused;
+	struct i915_pagetab *pt;
 	uint64_t temp;
 	uint32_t pde;
 
-	gen8_for_each_pde(unused, pd, start, length, temp, pde) {
-		BUG_ON(unused);
-		pd->page_tables[pde] = alloc_pt_single(dev);
-		if (IS_ERR(pd->page_tables[pde]))
+	gen8_for_each_pde(pt, pd, start, length, temp, pde) {
+		/* Don't reallocate page tables */
+		if (pt) {
+			/* Scratch is never allocated this way */
+			WARN_ON(pt->scratch);
+			/* If there is a zombie, we can reuse it and save time
+			 * on the allocation. If we clear the zombie status and
+			 * the caller somehow fails, we'll probably hit some
+			 * assertions, so it's up to them to fix up the bitmaps.
+			 */
+			continue;
+		}
+
+		pt = alloc_pt_single(ppgtt->base.dev);
+		if (IS_ERR(pt))
 			goto unwind_out;
+
+		pd->page_tables[pde] = pt;
+		set_bit(pde, new_pts);
 	}
 
 	return 0;
 
 unwind_out:
-	while (pde--)
-		free_pt_single(pd->page_tables[pde], dev);
+	for_each_set_bit(pde, new_pts, I915_PDES_PER_PD)
+		free_pt_single(pd->page_tables[pde], ppgtt->base.dev);
 
 	return -ENOMEM;
 }
 
-/* bitmap of new pagedirs */
-static int gen8_ppgtt_alloc_pagedirs(struct i915_pagedirpo *pdp,
+/**
+ * gen8_ppgtt_alloc_pagedirs() - Allocate page directories for VA range.
+ * @ppgtt:	Master ppgtt structure.
+ * @pdp:	Page directory pointer for this address range.
+ * @start:	Starting virtual address to begin allocations.
+ * @length	Size of the allocations.
+ * @new_pds	Bitmap set by function with new allocations. Likely used by the
+ *		caller to free on error.
+ *
+ * Allocate the required number of page directories starting at the pde index of
+ * @start, and ending at the pde index @start + @length. This function will skip
+ * over already allocated page directories within the range, and only allocate
+ * new ones, setting the appropriate pointer within the pdp as well as the
+ * correct position in the bitmap @new_pds.
+ *
+ * The function will only allocate the pages within the range for a give page
+ * directory pointer. In other words, if @start + @length straddles a virtually
+ * addressed PDP boundary (512GB for 4k pages), there will be more allocations
+ * required by the caller, This is not currently possible, and the BUG in the
+ * code will prevent it.
+ *
+ * Return: 0 if success; negative error code otherwise.
+ */
+static int gen8_ppgtt_alloc_pagedirs(struct i915_hw_ppgtt *ppgtt,
+				     struct i915_pagedirpo *pdp,
 				     uint64_t start,
 				     uint64_t length,
-				     struct drm_device *dev)
+				     unsigned long *new_pds)
 {
-	struct i915_pagedir *unused;
+	struct i915_pagedir *pd;
 	uint64_t temp;
 	uint32_t pdpe;
 
+	BUG_ON(!bitmap_empty(new_pds, GEN8_LEGACY_PDPES));
+
 	/* FIXME: PPGTT container_of won't work for 64b */
 	BUG_ON((start + length) > 0x800000000ULL);
 
-	gen8_for_each_pdpe(unused, pdp, start, length, temp, pdpe) {
-		BUG_ON(unused);
-		pdp->pagedirs[pdpe] = alloc_pd_single(dev);
+	gen8_for_each_pdpe(pd, pdp, start, length, temp, pdpe) {
+		if (pd)
+			continue;
 
-		if (IS_ERR(pdp->pagedirs[pdpe]))
+		pd = alloc_pd_single(ppgtt->base.dev);
+		if (IS_ERR(pd))
 			goto unwind_out;
+
+		pdp->pagedirs[pdpe] = pd;
+		set_bit(pdpe, new_pds);
 	}
 
 	return 0;
 
 unwind_out:
-	while (pdpe--)
-		free_pd_single(pdp->pagedirs[pdpe], dev);
+	for_each_set_bit(pdpe, new_pds, GEN8_LEGACY_PDPES)
+		free_pd_single(pdp->pagedirs[pdpe], ppgtt->base.dev);
+
+	return -ENOMEM;
+}
+
+static inline void
+free_gen8_temp_bitmaps(unsigned long *new_pds, unsigned long **new_pts)
+{
+	int i;
+	for (i = 0; i < GEN8_LEGACY_PDPES; i++)
+		kfree(new_pts[i]);
+	kfree(new_pts);
+	kfree(new_pds);
+}
+
+/* Fills in the page directory bitmap, ant the array of page tables bitmap. Both
+ * of these are based on the number of PDPEs in the system.
+ */
+int __must_check alloc_gen8_temp_bitmaps(unsigned long **new_pds,
+					 unsigned long ***new_pts)
+{
+	int i;
+	unsigned long *pds;
+	unsigned long **pts;
+
+	pds = kcalloc(BITS_TO_LONGS(GEN8_LEGACY_PDPES), sizeof(unsigned long), GFP_KERNEL);
+	if (!pds)
+		return -ENOMEM;
+
+	pts = kcalloc(I915_PDES_PER_PD, sizeof(unsigned long *), GFP_KERNEL);
+	if (!pts) {
+		kfree(pds);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < GEN8_LEGACY_PDPES; i++) {
+		pts[i] = kcalloc(BITS_TO_LONGS(I915_PDES_PER_PD),
+				 sizeof(unsigned long), GFP_KERNEL);
+		if (!pts[i])
+			goto err_out;
+	}
 
+	*new_pds = pds;
+	*new_pts = (unsigned long **)pts;
+
+	return 0;
+
+err_out:
+	free_gen8_temp_bitmaps(pds, pts);
 	return -ENOMEM;
 }
 
@@ -699,6 +847,7 @@ static int gen8_alloc_va_range(struct i915_address_space *vm,
 {
 	struct i915_hw_ppgtt *ppgtt =
 		container_of(vm, struct i915_hw_ppgtt, base);
+	unsigned long *new_page_dirs, **new_page_tables;
 	struct i915_pagedir *pd;
 	const uint64_t orig_start = start;
 	const uint64_t orig_length = length;
@@ -706,43 +855,103 @@ static int gen8_alloc_va_range(struct i915_address_space *vm,
 	uint32_t pdpe;
 	int ret;
 
-	/* Do the allocations first so we can easily bail out */
-	ret = gen8_ppgtt_alloc_pagedirs(&ppgtt->pdp, start, length,
-					ppgtt->base.dev);
+#ifndef CONFIG_64BIT
+	/* Disallow 64b address on 32b platforms. Nothing is wrong with doing
+	 * this in hardware, but a lot of the drm code is not prepared to handle
+	 * 64b offset on 32b platforms. */
+	if (start + length > 0x100000000ULL)
+		return -E2BIG;
+#endif
+
+	/* Wrap is never okay since we can only represent 48b, and we don't
+	 * actually use the other side of the canonical address space.
+	 */
+	if (WARN_ON(start + length < start))
+		return -ERANGE;
+
+	ret = alloc_gen8_temp_bitmaps(&new_page_dirs, &new_page_tables);
 	if (ret)
 		return ret;
 
+	/* Do the allocations first so we can easily bail out */
+	ret = gen8_ppgtt_alloc_pagedirs(ppgtt, &ppgtt->pdp, start, length,
+					new_page_dirs);
+	if (ret) {
+		free_gen8_temp_bitmaps(new_page_dirs, new_page_tables);
+		return ret;
+	}
+
+	/* For every page directory referenced, allocate page tables */
 	gen8_for_each_pdpe(pd, &ppgtt->pdp, start, length, temp, pdpe) {
-		ret = gen8_ppgtt_alloc_pagetabs(pd, start, length,
-						ppgtt->base.dev);
+		bitmap_zero(new_page_tables[pdpe], I915_PDES_PER_PD);
+		ret = gen8_ppgtt_alloc_pagetabs(ppgtt, pd, start, length,
+						new_page_tables[pdpe]);
 		if (ret)
 			goto err_out;
 	}
 
-	/* Now mark everything we've touched as used. This doesn't allow for
-	 * robust error checking, but it makes the code a hell of a lot simpler.
-	 */
 	start = orig_start;
 	length = orig_length;
 
+	/* Allocations have completed successfully, so set the bitmaps, and do
+	 * the mappings. */
 	gen8_for_each_pdpe(pd, &ppgtt->pdp, start, length, temp, pdpe) {
+		gen8_ppgtt_pde_t *const pagedir = kmap_atomic(pd->page);
 		struct i915_pagetab *pt;
 		uint64_t pd_len = gen8_clamp_pd(start, length);
 		uint64_t pd_start = start;
 		uint32_t pde;
-		gen8_for_each_pde(pt, &ppgtt->pd, pd_start, pd_len, temp, pde) {
-			bitmap_set(pd->page_tables[pde]->used_ptes,
-				   gen8_pte_index(start),
-				   gen8_pte_count(start, length));
+
+		/* Every pd should be allocated, we just did that above. */
+		BUG_ON(!pd);
+
+		gen8_for_each_pde(pt, pd, pd_start, pd_len, temp, pde) {
+			/* Same reasoning as pd */
+			BUG_ON(!pt);
+			BUG_ON(!pd_len);
+			BUG_ON(!gen8_pte_count(pd_start, pd_len));
+
+			/* Set our used ptes within the page table */
+			bitmap_set(pt->used_ptes,
+				   gen8_pte_index(pd_start),
+				   gen8_pte_count(pd_start, pd_len));
+
+			/* Our pde is now pointing to the pagetable, pt */
 			set_bit(pde, pd->used_pdes);
+
+			/* Map the PDE to the page table */
+			__gen8_do_map_pt(pagedir + pde, pt, vm->dev);
+
+			/* NB: We haven't yet mapped ptes to pages. At this
+			 * point we're still relying on insert_entries() */
+
+			/* No longer possible this page table is a zombie */
+			pt->zombie = 0;
 		}
+
+		if (!HAS_LLC(vm->dev))
+			drm_clflush_virt_range(pagedir, PAGE_SIZE);
+
+		kunmap_atomic(pagedir);
+
 		set_bit(pdpe, ppgtt->pdp.used_pdpes);
+		/* This pd is officially not a zombie either */
+		ppgtt->pdp.pagedirs[pdpe]->zombie = 0;
 	}
 
+	free_gen8_temp_bitmaps(new_page_dirs, new_page_tables);
 	return 0;
 
 err_out:
-	gen8_teardown_va_range(vm, orig_start, start);
+	while (pdpe--) {
+		for_each_set_bit(temp, new_page_tables[pdpe], I915_PDES_PER_PD)
+			free_pt_single(pd->page_tables[temp], vm->dev);
+	}
+
+	for_each_set_bit(pdpe, new_page_dirs, GEN8_LEGACY_PDPES)
+		free_pd_single(ppgtt->pdp.pagedirs[pdpe], vm->dev);
+
+	free_gen8_temp_bitmaps(new_page_dirs, new_page_tables);
 	return ret;
 }
 
@@ -753,37 +962,68 @@ err_out:
  * space.
  *
  */
-static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt, uint64_t size)
+static int gen8_ppgtt_init_common(struct i915_hw_ppgtt *ppgtt, uint64_t size)
 {
-	struct i915_pagedir *pd;
-	uint64_t temp, start = 0;
-	const uint64_t orig_length = size;
-	uint32_t pdpe;
-	int ret;
+	ppgtt->scratch_pd = alloc_pt_scratch(ppgtt->base.dev);
+	if (IS_ERR(ppgtt->scratch_pd))
+		return PTR_ERR(ppgtt->scratch_pd);
 
 	ppgtt->base.start = 0;
 	ppgtt->base.total = size;
-	ppgtt->base.clear_range = gen8_ppgtt_clear_range;
-	ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
 	ppgtt->base.cleanup = gen8_ppgtt_cleanup;
+	ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
+
 	ppgtt->switch_mm = gen8_mm_switch;
 
-	ppgtt->scratch_pd = alloc_pt_scratch(ppgtt->base.dev);
-	if (IS_ERR(ppgtt->scratch_pd))
-		return PTR_ERR(ppgtt->scratch_pd);
+	return 0;
+}
+
+static int gen8_aliasing_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
+{
+	struct drm_device *dev = ppgtt->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct i915_pagedir *pd;
+	uint64_t temp, start = 0, size = dev_priv->gtt.base.total;
+	uint32_t pdpe;
+	int ret;
 
+	ret = gen8_ppgtt_init_common(ppgtt, dev_priv->gtt.base.total);
+	if (ret)
+		return ret;
+
+	/* Aliasing PPGTT has to always work and be mapped because of the way we
+	 * use RESTORE_INHIBIT in the context switch. This will be fixed
+	 * eventually. */
 	ret = gen8_alloc_va_range(&ppgtt->base, start, size);
 	if (ret) {
 		free_pt_scratch(ppgtt->scratch_pd, ppgtt->base.dev);
 		return ret;
 	}
 
-	start = 0;
-	size = orig_length;
-
 	gen8_for_each_pdpe(pd, &ppgtt->pdp, start, size, temp, pdpe)
 		gen8_map_pagetable_range(pd, start, size, ppgtt->base.dev);
 
+	ppgtt->base.allocate_va_range = NULL;
+	ppgtt->base.teardown_va_range = NULL;
+	ppgtt->base.clear_range = gen8_ppgtt_clear_range;
+
+	return 0;
+}
+
+static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
+{
+	struct drm_device *dev = ppgtt->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int ret;
+
+	ret = gen8_ppgtt_init_common(ppgtt, dev_priv->gtt.base.total);
+	if (ret)
+		return ret;
+
+	ppgtt->base.allocate_va_range = gen8_alloc_va_range;
+	ppgtt->base.teardown_va_range = gen8_teardown_va_range;
+	ppgtt->base.clear_range = NULL;
+
 	return 0;
 }
 
@@ -1315,9 +1555,9 @@ static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt, bool aliasing)
 	if (ret)
 		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.allocate_va_range = aliasing ? NULL : gen6_alloc_va_range;
+	ppgtt->base.teardown_va_range = aliasing ? NULL : gen6_teardown_va_range;
+	ppgtt->base.clear_range = aliasing ? gen6_ppgtt_clear_range : NULL;
 	ppgtt->base.insert_entries = gen6_ppgtt_insert_entries;
 	ppgtt->base.cleanup = gen6_ppgtt_cleanup;
 	ppgtt->base.start = 0;
@@ -1355,8 +1595,10 @@ static int __hw_ppgtt_init(struct drm_device *dev, struct i915_hw_ppgtt *ppgtt,
 
 	if (INTEL_INFO(dev)->gen < 8)
 		return gen6_ppgtt_init(ppgtt, aliasing);
+	else if ((IS_GEN8(dev) || IS_GEN9(dev)) && aliasing)
+		return gen8_aliasing_ppgtt_init(ppgtt);
 	else if (IS_GEN8(dev) || IS_GEN9(dev))
-		return gen8_ppgtt_init(ppgtt, dev_priv->gtt.base.total);
+		return gen8_ppgtt_init(ppgtt);
 	else
 		BUG();
 }
@@ -1370,8 +1612,9 @@ int i915_ppgtt_init(struct drm_device *dev, struct i915_hw_ppgtt *ppgtt)
 		kref_init(&ppgtt->ref);
 		drm_mm_init(&ppgtt->base.mm, ppgtt->base.start,
 			    ppgtt->base.total);
-		ppgtt->base.clear_range(&ppgtt->base, 0,
-			    ppgtt->base.total, true);
+		if (ppgtt->base.clear_range)
+			ppgtt->base.clear_range(&ppgtt->base, 0,
+				ppgtt->base.total, true);
 		i915_init_vm(dev_priv, &ppgtt->base);
 	}
 
@@ -1489,10 +1732,7 @@ ppgtt_bind_vma(struct i915_vma *vma,
 
 static void ppgtt_unbind_vma(struct i915_vma *vma)
 {
-	vma->vm->clear_range(vma->vm,
-			     vma->node.start,
-			     vma->obj->base.size,
-			     true);
+	WARN_ON(vma->vm->teardown_va_range && vma->vm->clear_range);
 	if (vma->vm->teardown_va_range) {
 		trace_i915_va_teardown(vma->vm,
 				       vma->node.start, vma->node.size,
@@ -1501,7 +1741,14 @@ static void ppgtt_unbind_vma(struct i915_vma *vma)
 		vma->vm->teardown_va_range(vma->vm,
 					   vma->node.start, vma->node.size);
 		ppgtt_invalidate_tlbs(vma->vm);
-	}
+	} else if (vma->vm->clear_range) {
+		vma->vm->clear_range(vma->vm,
+				     vma->node.start,
+				     vma->obj->base.size,
+				     true);
+	} else
+		BUG();
+
 }
 
 extern int intel_iommu_gfx_mapped;
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 120f213..947d214 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -177,13 +177,26 @@ struct i915_vma {
 			u32 flags);
 };
 
-
+/* Zombies. We write page tables with the CPU, and hardware switches them with
+ * the GPU. As such, the only time we can safely remove a page table is when we
+ * know the context is idle. Since we have no good way to do this, we use the
+ * zombie.
+ *
+ * Under memory pressure, if the system is idle, zombies may be reaped.
+ *
+ * There are 3 states a page table can be in (not including scratch)
+ *  bitmap = 0, zombie = 0: unallocated
+ *  bitmap = 1, zombie = 0: allocated
+ *  bitmap = 0, zombie = 1: zombie
+ *  bitmap = 1, zombie = 1: invalid
+ */
 struct i915_pagetab {
 	struct page *page;
 	dma_addr_t daddr;
 
 	unsigned long *used_ptes;
 	unsigned int scratch:1;
+	unsigned zombie:1;
 };
 
 struct i915_pagedir {
@@ -195,6 +208,7 @@ struct i915_pagedir {
 
 	unsigned long *used_pdes;
 	struct i915_pagetab *page_tables[I915_PDES_PER_PD];
+	unsigned zombie:1;
 };
 
 struct i915_pagedirpo {
