vga: adjust dirty memory region if pel panning is active

When pel panning is active, one more byte is read from each of the VGA
memory planes.  This has to be accounted in the computation of region_end,
otherwise vga_draw_graphic() fails an assertion:

qemu-system-i386: ../system/physmem.c:946: cpu_physical_memory_snapshot_get_dirty: Assertion `start + length <= snap->end' failed.

Reported-by: Helge Konetzka <hk@zapateado.de>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2244
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/hw/display/vga.c b/hw/display/vga.c
index b4ceff70eb890c791f5b87bda6403fa0bcf3e853..40acd19e72ab1415db777953959355b368a34a89 100644 (file)
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1571,11 +1571,15 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
             break;
         }
     }
+    hpel = bits <= 8 ? s->params.hpel : 0;
 
     region_start = (s->params.start_addr * 4);
     region_end = region_start + (ram_addr_t)s->params.line_offset * height;
     region_end += width * depth / 8; /* scanline length */
     region_end -= s->params.line_offset;
+    if (hpel) {
+        region_end += 4;
+    }
     if (region_end > s->vbe_size || depth == 0 || depth == 15) {
         /*
          * We land here on:
@@ -1660,7 +1664,6 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
            width, height, v, line_offset, s->cr[9], s->cr[VGA_CRTC_MODE],
            s->params.line_compare, sr(s, VGA_SEQ_CLOCK_MODE));
 #endif
-    hpel = bits <= 8 ? s->params.hpel : 0;
     addr1 = (s->params.start_addr * 4);
     bwidth = DIV_ROUND_UP(width * bits, 8);
     if (hpel) {