Re: [Qemu-devel] Bug with qxl vga memory settings

[Gerd Hoffmann]

On 01/25/13 15:37, Fabio Fantoni wrote:
> Debugging qxl problem with xen I tested first qemu without xen and I
> found that qxl memory mapping problem is not only xen related.
> After some tests with qemu-only I found that -global qxl-vga.vram_size=N
> and -global qxl-vga.ram_size=N (where N is for example 16384 or 65536)
> are bugged.

ram_size + vram_size want bytes not kilobytes.

> Qxl ram regions with these parameters on all test are always:
> 
> qxl-0: ram/pri: 32 MB [region 0]
> qxl-0: vram/32: 0 MB [region 1]

Yep.  You'll get the minimum supported sizes due to the small numbers.

> Qemu crashes when start using qxl.

Oops.  That shouldn't happen of course, I'll have a look.

> With -global qxl-vga.vram_size_mb=N and -global qxl-vga.ram_size_mb=N it
> seems correctly working.

Ah, you've found the more user-friendly versions which accept megabytes
instead of bytes.

> For example I saw that on ALL tests with right qxl memory region 0 and 1
> there is also another unmapped region > 0 mb.

The rom bar maybe?  seabios maps that only temporary to load the vgabios.

> Is it correct or is it wrong and can be the cause of crash with xen if
> qemu search for videoram > region0+region1?
> qxl-0: ram/pri: 32 MB [region 0]
> qxl-0: vram/32: 32 MB [region 1]
> qxl-0: vram/64: 32 MB [unmapped]

vram/64 is a mirror of vram/32, but in a 64bit capable pci bar.  It will
show up if you make vram64_size_mb larger than vram_size_mb and allows
pretty big vram bars for 64bit guests.

> I saw also that qemu 1.3 debian package use vgabios from vgabios 0.7
> package instead of seabios 1.7.2 package.
> Can be a problem with qxl?

Both should work (assuming vgabios is taken from the repo @ qemu.org).

cheers,
  Gerd