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[Qemu-devel] Re: pc-bios/bios.bin - where it comes from?


From: Anthony Liguori
Subject: [Qemu-devel] Re: pc-bios/bios.bin - where it comes from?
Date: Thu, 04 Mar 2010 21:50:27 -0600
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On 03/04/2010 04:46 PM, Michael Tokarev wrote:
Hello.

There are a few bugs filed about an.. interesting
behavour.  For example:

  http://www.mail-archive.com/address@hidden/msg29834.html
  https://bugs.launchpad.net/qemu/+bug/513273

After quite some mix-n-matching, at least on my test machine,
I can say that the issue gets triggered by seabios.  When
using pc-bios/bios.bin everything is ok.  But when using
any other bios.bin, even downloading seabios-0.5.1.tar.gz
and building it - on a debian lenny system anyway - by
running `make', the problem triggers.

I tried different versions/variations of vgabios.bin
(it's only -vga std which triggers the issue so far),
including 0.6b and 0.6c built from sources, vgabios.bin
from debian packages (0.6b and 0.6c), and the one
included in qemu-0.12.3.tar.gz.  And my conclusion
so far is that vgabios.bin has exactly _no_ effect on
the issue.

But when using bios.bin from qemu-kvm-0.12.3.tar.gz,
and _only_ that bios.bin, the problem goes away.

pc-bios/bios.bin gets built from roms/seabios.

We don't ship seabios 0.5.1 in 0.12.3, we ship 0.5.1-stable which is two commits ahead of 0.5.1.

So the question arises: where that pc-bios/bios.bin
comes from into qemu-0.12.3.tar.gz?  It is either
built from some other sources (not from seabios-0.5.1),
or built with some extra/different compiler/linker options,
or built using different compiler/linker.

This is partially confirmed on ubuntu as well, but,
as far as I understand, there the behavour is different
with different versions of vgabios.

One of the reasons we include a git submodule and the source for the bios is so that distributors don't have to deal with building the packages independently. Morale of the story is, just use the source we ship and don't try to be more clever than that :-)

In case it's not clear: I'm testing qemu-kvm-0.12.3;
bios.bin is the same in qemu-0.12.3 and qemu-kvm-0.12.3.

BTW, is there any reason preventing updating vgabios
to 0.6c version - the latest released one?

There's no compelling improvement in 0.6c and updating vgabios is not something I'm eager to do unless there's a strong justification.

Regards,

Anthony Liguori



Thanks!

/mjt
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