vga display update mis-calculated the region for the dirty bitmap
snapshot in case the scanlines are padded.  This can triggere an
assert in cpu_physical_memory_snapshot_get_dirty().

Fixes: fec5e8c92becad223df9d972770522f64aafdb72
Reported-by: Kevin Wolf <kwolf@redhat.com>
Reported-by: 李强 <liqiang6-s@360.cn>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/display/vga.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/display/vga.c b/hw/display/vga.c
index b2516c8d21..dcc95f88e2 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1630,7 +1630,7 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
     if (!full_update) {
         vga_sync_dirty_bitmap(s);
         snap = memory_region_snapshot_and_clear_dirty(&s->vram, addr1,
-                                                      bwidth * height,
+                                                      line_offset * height,
                                                       DIRTY_MEMORY_VGA);
     }
 
-- 
2.9.3