drm/nv50: align size of buffer object to the right boundaries.

- In the current situation the padding that is added is dangerous to write
  to, userspace could potentially overwrite parts of another bo.
- Depth and stencil buffers are supposed to be large enough in general so
  the waste of memory should be acceptable.
- Alternatives are hiding the padding from users or splitting vram into 2
  zones.

Signed-off-by: Maarten Maathuis <madman2003@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index db0ed4c..028719f 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -65,8 +65,10 @@ nouveau_bo_fixup_align(struct drm_device *dev,
 
        /*
         * Some of the tile_flags have a periodic structure of N*4096 bytes,
-        * align to to that as well as the page size. Overallocate memory to
-        * avoid corruption of other buffer objects.
+        * align to to that as well as the page size. Align the size to the
+        * appropriate boundaries. This does imply that sizes are rounded up
+        * 3-7 pages, so be aware of this and do not waste memory by allocating
+        * many small buffers.
         */
        if (dev_priv->card_type == NV_50) {
                uint32_t block_size = nouveau_mem_fb_amount(dev) >> 15;
@@ -77,22 +79,20 @@ nouveau_bo_fixup_align(struct drm_device *dev,
                case 0x2800:
                case 0x4800:
                case 0x7a00:
-                       *size = roundup(*size, block_size);
                        if (is_power_of_2(block_size)) {
-                               *size += 3 * block_size;
                                for (i = 1; i < 10; i++) {
                                        *align = 12 * i * block_size;
                                        if (!(*align % 65536))
                                                break;
                                }
                        } else {
-                               *size += 6 * block_size;
                                for (i = 1; i < 10; i++) {
                                        *align = 8 * i * block_size;
                                        if (!(*align % 65536))
                                                break;
                                }
                        }
+                       *size = roundup(*size, *align);
                        break;
                default:
                        break;