[PATCH] drm/virtio: Use vmalloc for command buffer allocations.

[David Riley]

Userspace requested command buffer allocations could be too large
to make as a contiguous allocation.  Use vmalloc if necessary to
satisfy those allocations.

Signed-off-by: David Riley <davidriley at chromium.org>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c |  4 +-
 drivers/gpu/drm/virtio/virtgpu_vq.c    | 74 ++++++++++++++++++++++++--
 2 files changed, 73 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index ac60be9b5c19..a8732a8af766 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -195,7 +195,7 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		goto out_free;
 
-	buf = memdup_user(u64_to_user_ptr(exbuf->command), exbuf->size);
+	buf = vmemdup_user(u64_to_user_ptr(exbuf->command), exbuf->size);
 	if (IS_ERR(buf)) {
 		ret = PTR_ERR(buf);
 		goto out_unresv;
@@ -230,7 +230,7 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 	return 0;
 
 out_memdup:
-	kfree(buf);
+	kvfree(buf);
 out_unresv:
 	ttm_eu_backoff_reservation(&ticket, &validate_list);
 out_free:
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index 981ee16e3ee9..bcbc48b7284f 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -154,7 +154,7 @@ static void free_vbuf(struct virtio_gpu_device *vgdev,
 {
 	if (vbuf->resp_size > MAX_INLINE_RESP_SIZE)
 		kfree(vbuf->resp_buf);
-	kfree(vbuf->data_buf);
+	kvfree(vbuf->data_buf);
 	kmem_cache_free(vgdev->vbufs, vbuf);
 }
 
@@ -251,6 +251,59 @@ void virtio_gpu_dequeue_cursor_func(struct work_struct *work)
 	wake_up(&vgdev->cursorq.ack_queue);
 }
 
+/* How many bytes left in this page. */
+static unsigned int rest_of_page(void *data)
+{
+	return PAGE_SIZE - offset_in_page(data);
+}
+
+/* Create sg_table from a vmalloc'd buffer. */
+static struct sg_table *vmalloc_to_sgt(char *data, uint32_t size)
+{
+	int nents, ret, s, i;
+	struct sg_table *sgt;
+	struct scatterlist *sg;
+	struct page *pg;
+
+	sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
+	if (!sgt)
+		return NULL;
+
+	nents = DIV_ROUND_UP(size, PAGE_SIZE) + 1;
+	ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
+	if (ret) {
+		kfree(sgt);
+		return NULL;
+	}
+
+	for_each_sg(sgt->sgl, sg, nents, i) {
+		pg = vmalloc_to_page(data);
+		if (!pg) {
+			sg_free_table(sgt);
+			kfree(sgt);
+			return NULL;
+		}
+
+		s = rest_of_page(data);
+		if (s > size)
+			s = size;
+
+		sg_set_page(sg, pg, s, offset_in_page(data));
+
+		size -= s;
+		data += s;
+
+		if (size) {
+			sg_unmark_end(sg);
+		} else {
+			sg_mark_end(sg);
+			break;
+		}
+	}
+
+	return sgt;
+}
+
 static int virtio_gpu_queue_ctrl_buffer_locked(struct virtio_gpu_device *vgdev,
 					       struct virtio_gpu_vbuffer *vbuf)
 		__releases(&vgdev->ctrlq.qlock)
@@ -260,6 +313,7 @@ static int virtio_gpu_queue_ctrl_buffer_locked(struct virtio_gpu_device *vgdev,
 	struct scatterlist *sgs[3], vcmd, vout, vresp;
 	int outcnt = 0, incnt = 0;
 	int ret;
+	struct sg_table *sgt = NULL;
 
 	if (!vgdev->vqs_ready)
 		return -ENODEV;
@@ -269,8 +323,17 @@ static int virtio_gpu_queue_ctrl_buffer_locked(struct virtio_gpu_device *vgdev,
 	outcnt++;
 
 	if (vbuf->data_size) {
-		sg_init_one(&vout, vbuf->data_buf, vbuf->data_size);
-		sgs[outcnt + incnt] = &vout;
+		if (is_vmalloc_addr(vbuf->data_buf)) {
+			spin_unlock(&vgdev->ctrlq.qlock);
+			sgt = vmalloc_to_sgt(vbuf->data_buf, vbuf->data_size);
+			spin_lock(&vgdev->ctrlq.qlock);
+			if (!sgt)
+				return -ENOMEM;
+			sgs[outcnt + incnt] = sgt->sgl;
+		} else {
+			sg_init_one(&vout, vbuf->data_buf, vbuf->data_size);
+			sgs[outcnt + incnt] = &vout;
+		}
 		outcnt++;
 	}
 
@@ -294,6 +357,11 @@ static int virtio_gpu_queue_ctrl_buffer_locked(struct virtio_gpu_device *vgdev,
 		virtqueue_kick(vq);
 	}
 
+	if (sgt) {
+		sg_free_table(sgt);
+		kfree(sgt);
+	}
+
 	if (!ret)
 		ret = vq->num_free;
 	return ret;
-- 
2.23.0.187.g17f5b7556c-goog