Re: [Qemu-devel] [PATCH 6/6] kvm: qemu: fix vga screendump

["andrzej zaborowski" <balrogg@gmail.com>]

2008/7/17 Anthony Liguori <aliguori@us.ibm.com>:
> From: Avi Kivity <avi@qumranet.com>
> Commit 737d2050 ("Implement resolution switching in common console code")
> uses qemu_console_resize() instead of dpy_resize().  This means console->ds
> is examined instead of the VGA private ds, and the resize does not take place,
> leading to a segfault.
>
> Fix by modifying the DisplayState directly rather than swapping the pointer.

The screen dumping is hacky but maybe it's a good idea to keep the
hacks local to hw/vga.c, with something like the following diff.  I
think we need to fix the screen dumping globally (some graphic cards
will need fixing too).

diff --git a/console.c b/console.c
index 1c94980..bc0c349 100644
--- a/console.c
+++ b/console.c
@@ -1334,8 +1334,7 @@ CharDriverState *text_console_init(DisplayState
*ds, const char *p)

 void qemu_console_resize(QEMUConsole *console, int width, int height)
 {
-    if (console->g_width != width || console->g_height != height
-        || !console->ds->data) {
+    if (console->g_width != width || console->g_height != height) {
         console->g_width = width;
         console->g_height = height;
         if (active_console == console) {
diff --git a/hw/vga.c b/hw/vga.c
index 5a3203c..5c66209 100644
--- a/hw/vga.c
+++ b/hw/vga.c
@@ -2228,8 +2228,6 @@ int pci_vga_init(PCIBus *bus, DisplayState *ds,
uint8_t *vga_ram_base,
 /********************************************************/
 /* vga screen dump */

-static int vga_save_w, vga_save_h;
-
 static void vga_save_dpy_update(DisplayState *s,
                                 int x, int y, int w, int h)
 {
@@ -2237,10 +2235,14 @@ static void vga_save_dpy_update(DisplayState *s,

 static void vga_save_dpy_resize(DisplayState *s, int w, int h)
 {
+}
+
+static void vga_save_dpy_alloc(DisplayState *s, int w, int h)
+{
     s->linesize = w * 4;
     s->data = qemu_malloc(h * s->linesize);
-    vga_save_w = w;
-    vga_save_h = h;
+    s->width = w;
+    s->height = h;
 }

 static void vga_save_dpy_refresh(DisplayState *s)
@@ -2281,26 +2283,27 @@ int ppm_save(const char *filename, uint8_t *data,
 static void vga_screen_dump(void *opaque, const char *filename)
 {
     VGAState *s = (VGAState *)opaque;
-    DisplayState *saved_ds, ds1, *ds = &ds1;
+    DisplayState saved_ds, *ds = s->ds;

     /* XXX: this is a little hackish */
-    vga_invalidate_display(s);
-    saved_ds = s->ds;
+    saved_ds = *s->ds;

     memset(ds, 0, sizeof(DisplayState));
     ds->dpy_update = vga_save_dpy_update;
     ds->dpy_resize = vga_save_dpy_resize;
     ds->dpy_refresh = vga_save_dpy_refresh;
     ds->depth = 32;
+    qemu_console_resize(s->console, -1, -1);

-    s->ds = ds;
     s->graphic_mode = -1;
+    ds->dpy_resize = vga_save_dpy_alloc;
+    vga_invalidate_display(s);
     vga_update_display(s);

     if (ds->data) {
-        ppm_save(filename, ds->data, vga_save_w, vga_save_h,
-                 s->ds->linesize);
+        ppm_save(filename, ds->data, ds->width, ds->height, ds->linesize);
+
         qemu_free(ds->data);
     }
-    s->ds = saved_ds;
+    *s->ds = saved_ds;
 }