drm/vmwgfx: Fix a width / pitch mismatch on framebuffer updates

When the framebuffer is a vmwgfx dma buffer and a proxy surface is
created, the vmw_kms_update_proxy() function requires that the proxy
surface width and the framebuffer pitch are compatible, otherwise
display corruption occurs as seen in gnome-shell/native with software
3D. Since the framebuffer pitch is determined by user-space, allocate
a proxy surface the width of which is based on the framebuffer pitch
rather than on the framebuffer width.

Cc: <stable@vger.kernel.org>
Reported-by: Raphael Hertzog <buxy@kali.org>
Tested-by:  Mati Aharoni <muts@kali.org>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

@@ -763,21 +763,25 @@ static int vmw_create_dmabuf_proxy(struct drm_device *dev,
 	uint32_t format;
 	struct drm_vmw_size content_base_size;
 	struct vmw_resource *res;
+	unsigned int bytes_pp;
 	int ret;
 
 	switch (mode_cmd->depth) {
 	case 32:
 	case 24:
 		format = SVGA3D_X8R8G8B8;
+		bytes_pp = 4;
 		break;
 
 	case 16:
 	case 15:
 		format = SVGA3D_R5G6B5;
+		bytes_pp = 2;
 		break;
 
 	case 8:
 		format = SVGA3D_P8;
+		bytes_pp = 1;
 		break;
 
 	default:
@@ -785,7 +789,7 @@ static int vmw_create_dmabuf_proxy(struct drm_device *dev,
 		return -EINVAL;
 	}
 
-	content_base_size.width  = mode_cmd->width;
+	content_base_size.width  = mode_cmd->pitch / bytes_pp;
 	content_base_size.height = mode_cmd->height;
 	content_base_size.depth  = 1;