semantic: 0.200
other: 0.145
device: 0.095
socket: 0.082
PID: 0.067
debug: 0.065
graphic: 0.063
files: 0.059
vnc: 0.047
performance: 0.042
network: 0.037
boot: 0.035
permissions: 0.033
KVM: 0.029
files: 0.180
debug: 0.164
semantic: 0.133
other: 0.114
PID: 0.062
performance: 0.056
graphic: 0.047
network: 0.047
device: 0.046
socket: 0.042
boot: 0.036
vnc: 0.030
KVM: 0.026
permissions: 0.017

unsupported screen resolution crashes sdl-qemu

if the (windows) guest sets a screen resolution that the SDL backend does not support,
qemu does an exit(1).
with this fix, the the resolution is still wrong (only part of the desktop is displayed),
but qemu keeps running and the guest can auto-revert the video mode:

ui/sdl.c:do_sdl_resize()
    SDL_Surface * tmp_screen;
    tmp_screen = SDL_SetVideoMode(width, height, bpp, flags);
    if (!tmp_screen) {
//      fprintf(stderr, "Could not open SDL display (%dx%dx%d): %s\n", width, 
//              height, bpp, SDL_GetError());
//      exit(1);
    } else {
        real_screen = tmp_screen;
    }

Sorry, a little confusion what's the problem you want to solve?

its in the first sentence. let me rephrase: the (windows) guest can select some screen resolution which SDL cannot
provide. what happens is that qemu quits without giving the quest a chance to shut down. thats like having a monitor
that crashes windows when it doesnt support the video mode.

Yes, it is a bug. It should go back to the previous setting if the new screen resolution falied.
I will send a patch later. 

Thanks.

Patch posted:

http://patchwork.ozlabs.org/patch/270084/

this patch does solve the problem

Patch has been included here a while ago already:
http://git.qemu.org/?p=qemu.git;a=commitdiff;h=898ae2846de4dcb1
... so this ticket could now be marked as fixed.