qxl: don't create too large primary surface

Limit primary to qemu vgamem size, to avoid reaching
qemu guest bug "requested primary larger than framebuffer"
on resizing screen too large to fit.

Remove unneeded and misleading variables.

Related to:
https://bugzilla.redhat.com/show_bug.cgi?id=1127552

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/qxl/qxl_display.c

@@ -572,7 +572,6 @@ static int qxl_crtc_mode_set(struct drm_crtc *crtc,
 	struct qxl_framebuffer *qfb;
 	struct qxl_bo *bo, *old_bo = NULL;
 	struct qxl_crtc *qcrtc = to_qxl_crtc(crtc);
-	uint32_t width, height, base_offset;
 	bool recreate_primary = false;
 	int ret;
 	int surf_id;
@@ -602,9 +601,10 @@ static int qxl_crtc_mode_set(struct drm_crtc *crtc,
 	if (qcrtc->index == 0)
 		recreate_primary = true;
 
-	width = mode->hdisplay;
-	height = mode->vdisplay;
-	base_offset = 0;
+	if (bo->surf.stride * bo->surf.height > qdev->vram_size) {
+		DRM_ERROR("Mode doesn't fit in vram size (vgamem)");
+		return -EINVAL;
+        }
 
 	ret = qxl_bo_reserve(bo, false);
 	if (ret != 0)
@@ -618,10 +618,10 @@ static int qxl_crtc_mode_set(struct drm_crtc *crtc,
 	if (recreate_primary) {
 		qxl_io_destroy_primary(qdev);
 		qxl_io_log(qdev,
-			   "recreate primary: %dx%d (was %dx%d,%d,%d)\n",
-			   width, height, bo->surf.width,
-			   bo->surf.height, bo->surf.stride, bo->surf.format);
-		qxl_io_create_primary(qdev, base_offset, bo);
+			   "recreate primary: %dx%d,%d,%d\n",
+			   bo->surf.width, bo->surf.height,
+			   bo->surf.stride, bo->surf.format);
+		qxl_io_create_primary(qdev, 0, bo);
 		bo->is_primary = true;
 	}