diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 814d894..4d48617 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -863,37 +863,13 @@ void i915_cmd_parser_fini_ring(struct intel_engine_cs *ring)
 static u32 *vmap_batch(struct drm_i915_gem_object *obj,
 		       unsigned start, unsigned len)
 {
-	int i;
-	void *addr = NULL;
-	struct sg_page_iter sg_iter;
-	int first_page = start >> PAGE_SHIFT;
-	int last_page = (len + start + 4095) >> PAGE_SHIFT;
-	int npages = last_page - first_page;
-	struct page **pages;
-
-	pages = drm_malloc_ab(npages, sizeof(*pages));
-	if (pages == NULL) {
-		DRM_DEBUG_DRIVER("Failed to get space for pages\n");
-		goto finish;
-	}
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, first_page) {
-		pages[i++] = sg_page_iter_page(&sg_iter);
-		if (i == npages)
-			break;
-	}
+	unsigned long first, npages;
 
-	addr = vmap(pages, i, 0, PAGE_KERNEL);
-	if (addr == NULL) {
-		DRM_DEBUG_DRIVER("Failed to vmap pages\n");
-		goto finish;
-	}
+	/* Convert [start, len) to pages */
+	first = start >> PAGE_SHIFT;
+	npages = DIV_ROUND_UP(start + len, PAGE_SIZE) - first;
 
-finish:
-	if (pages)
-		drm_free_large(pages);
-	return (u32*)addr;
+	return i915_gem_object_vmap_range(obj, first, npages);
 }
 
 /* Returns a vmap'd pointer to dest_obj, which the caller must unmap */
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a4dcb74..b3ae191 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2983,6 +2983,10 @@ static inline void i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
 	obj->pages_pin_count--;
 }
 
+void *__must_check i915_gem_object_vmap_range(struct drm_i915_gem_object *obj,
+					      unsigned long first,
+					      unsigned long npages);
+
 int __must_check i915_mutex_lock_interruptible(struct drm_device *dev);
 int i915_gem_object_sync(struct drm_i915_gem_object *obj,
 			 struct intel_engine_cs *to,
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 3d31d3a..d7c9ccd 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2400,6 +2400,65 @@ static void i915_gem_object_free_mmap_offset(struct drm_i915_gem_object *obj)
 	return 0;
 }
 
+/**
+ * i915_gem_object_vmap_range - map some or all of a GEM object into kernel space
+ * @obj: the GEM object to be mapped
+ * @first: offset in pages of the start of the range to be mapped
+ * @npages: length in pages of the range to be mapped. For convenience, a
+ *          length of zero is taken to mean "the remainder of the object"
+ *
+ * Map a given range of a GEM object into kernel virtual space.  The caller must
+ * make sure the associated pages are gathered and pinned before calling this
+ * function, and is responsible for unmapping the returned address when it is no
+ * longer required.
+ *
+ * Returns the address at which the object has been mapped, or NULL on failure.
+ */
+void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj,
+				 unsigned long first,
+				 unsigned long npages)
+{
+	unsigned long max_pages = obj->base.size >> PAGE_SHIFT;
+	struct scatterlist *sg = obj->pages->sgl;
+	struct sg_page_iter sg_iter;
+	struct page **pages;
+	unsigned long i = 0;
+	void *addr = NULL;
+
+	/* Minimal range check */
+	if (first + npages > max_pages) {
+		DRM_DEBUG_DRIVER("Invalid page range\n");
+		return NULL;
+	}
+
+	/* npages==0 is shorthand for "the rest of the object" */
+	if (npages == 0)
+		npages = max_pages - first;
+
+	pages = drm_malloc_gfp(npages, sizeof(*pages), GFP_TEMPORARY);
+	if (pages == NULL) {
+		DRM_DEBUG_DRIVER("Failed to get space for pages\n");
+		return NULL;
+	}
+
+	for_each_sg_page(sg, &sg_iter, max_pages, first) {
+		pages[i] = sg_page_iter_page(&sg_iter);
+		if (++i == npages) {
+			addr = vmap(pages, npages, 0, PAGE_KERNEL);
+			break;
+		}
+	}
+
+	/* We should have got here via the 'break' above */
+	WARN_ON(i != npages);
+	if (addr == NULL)
+		DRM_DEBUG_DRIVER("Failed to vmap pages\n");
+
+	drm_free_large(pages);
+
+	return addr;
+}
+
 void i915_vma_move_to_active(struct i915_vma *vma,
 			     struct drm_i915_gem_request *req)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 616f078..3a5d01a 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -108,9 +108,7 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 {
 	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
 	struct drm_device *dev = obj->base.dev;
-	struct sg_page_iter sg_iter;
-	struct page **pages;
-	int ret, i;
+	int ret;
 
 	ret = i915_mutex_lock_interruptible(dev);
 	if (ret)
@@ -129,16 +127,7 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 
 	ret = -ENOMEM;
 
-	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
-	if (pages == NULL)
-		goto err_unpin;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
-		pages[i++] = sg_page_iter_page(&sg_iter);
-
-	obj->dma_buf_vmapping = vmap(pages, i, 0, PAGE_KERNEL);
-	drm_free_large(pages);
+	obj->dma_buf_vmapping = i915_gem_object_vmap_range(obj, 0, 0);
 
 	if (!obj->dma_buf_vmapping)
 		goto err_unpin;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 8f52556..58a18e1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2064,27 +2064,6 @@ void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 	i915_gem_object_ggtt_unpin(ringbuf->obj);
 }
 
-static u32 *vmap_obj(struct drm_i915_gem_object *obj)
-{
-	struct sg_page_iter sg_iter;
-	struct page **pages;
-	void *addr;
-	int i;
-
-	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
-	if (pages == NULL)
-		return NULL;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
-		pages[i++] = sg_page_iter_page(&sg_iter);
-
-	addr = vmap(pages, i, 0, PAGE_KERNEL);
-	drm_free_large(pages);
-
-	return addr;
-}
-
 int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 				     struct intel_ringbuffer *ringbuf)
 {
@@ -2101,7 +2080,7 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 		if (ret)
 			goto unpin;
 
-		ringbuf->virtual_start = vmap_obj(obj);
+		ringbuf->virtual_start = i915_gem_object_vmap_range(obj, 0, 0);
 		if (ringbuf->virtual_start == NULL) {
 			ret = -ENOMEM;
 			goto unpin;
