[SeaBIOS] Boot failure with MS-Dos 6.22 (due to bad BIOS build?)

Daniel P. Berrange berrange at redhat.com
Wed Feb 29 10:19:52 CET 2012

On Wed, Feb 29, 2012 at 03:45:13AM -0500, Kevin O'Connor wrote:
> On Mon, Feb 27, 2012 at 04:25:09PM +0100, Jan Kiszka wrote:
> > On 2012-02-27 10:51, Daniel P. Berrange wrote:
> > > I'm seeing current QEMU GIT fail to boot MS-Dos 6.22 with the following
> > > crash:
> > > 
> > > # qemu-system-x86_64 -fda ~/MS-DOS\ 6.22.img  -m 1 -curses
> Does the error persist when run with "-m 2"?  If more memory fixes the
> issue, then it is likely already fixed in upstream (commit 890d9851).
> The bugs fixed in that commit are null pointer derefernce errors - in
> SeaBIOS, a write to "NULL" actually alters the memory at address 0,
> which can corrupt the interrupt table - these can lead to
> unpredictable errors, as the timing between when an irq fires and when
> the corruption occurs can vary.  DOS might overwrite the irq entries
> with its own settings, and thus depending on timing may cover up the
> error.  In short, I wouldn't assume the problem is the toolchain.

The error occurs no matter what '-m XX' setting I give it. I did a git
bisect across a Seabios GIT from master down torel- and could
not reproduce it with any BIOS I built myself. Hence the only conclusion
I could come to is that the QEMU binary was broken in some way.

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