vga: move computation of dirty memory region later

Move the computation of region_start and region_end after the value of
"bits" is known.  This makes it possible to distinguish modes that
support horizontal pel panning from modes that do not.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 25 insertions, 25 deletions

diff --git a/hw/display/vga.c b/hw/display/vga.c
index 4795a00..b4ceff7 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1501,31 +1501,6 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
     disp_width = width;
     depth = s->get_bpp(s);
 
-    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 (region_end > s->vbe_size || depth == 0 || depth == 15) {
-        /*
-         * We land here on:
-         *  - wraps around (can happen with cirrus vbe modes)
-         *  - depth == 0 (256 color palette video mode)
-         *  - depth == 15
-         *
-         * Take the safe and slow route:
-         *   - create a dirty bitmap snapshot for all vga memory.
-         *   - force shadowing (so all vga memory access goes
-         *     through vga_read_*() helpers).
-         *
-         * Given this affects only vga features which are pretty much
-         * unused by modern guests there should be no performance
-         * impact.
-         */
-        region_start = 0;
-        region_end = s->vbe_size;
-        force_shadow = true;
-    }
-
     /* bits 5-6: 0 = 16-color mode, 1 = 4-color mode, 2 = 256-color mode.  */
     shift_control = (s->gr[VGA_GFX_MODE] >> 5) & 3;
     double_scan = (s->cr[VGA_CRTC_MAX_SCAN] >> 7);
@@ -1597,6 +1572,31 @@ static void vga_draw_graphic(VGACommonState *s, int full_update)
         }
     }
 
+    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 (region_end > s->vbe_size || depth == 0 || depth == 15) {
+        /*
+         * We land here on:
+         *  - wraps around (can happen with cirrus vbe modes)
+         *  - depth == 0 (256 color palette video mode)
+         *  - depth == 15
+         *
+         * Take the safe and slow route:
+         *   - create a dirty bitmap snapshot for all vga memory.
+         *   - force shadowing (so all vga memory access goes
+         *     through vga_read_*() helpers).
+         *
+         * Given this affects only vga features which are pretty much
+         * unused by modern guests there should be no performance
+         * impact.
+         */
+        region_start = 0;
+        region_end = s->vbe_size;
+        force_shadow = true;
+    }
+
     /*
      * Check whether we can share the surface with the backend
      * or whether we need a shadow surface. We share native