7.0 RC2 kernel panic with Kqemu/AMD64

MFL Commissioner mfl-commissioner at marino.st
Sat Feb 16 19:10:39 UTC 2008

I would be happy to help debug this, although someone would have to give 
me step by step instructions on what to do exactly.
This is a development machine that (roughly) mirrors a production setup, 
so I have maintain the SMP/AMD64 configuration.
What I am still not quite clear on is this:  Is this a Qemu problem or 
FreeBSD kernel problem?

Anyway, I'll do what you ask to provide you with my backtraces, but I 
doubt that I will be able to interpret the results.

Juergen Lock wrote:
> On Sat, Feb 16, 2008 at 03:39:02AM -0600, John Marino wrote:
> Looks like you are running amd64 SMP, it is a known problem that kqemu
> doesn't really work in that case (see pkg-message of the qemu port);
> the exact cause of this is still unknown - the backtraces I got are rather
> weird and not really helpful, see this thread:
> 	http://lists.freebsd.org/pipermail/freebsd-emulation/2007-November/004182.html
> and there also is:
> 	http://www.freebsd.org/cgi/query-pr.cgi?pr=113430
> If you or anyone else wants to help debug this you are very welcome of
> course (it was suggested this might be a cache coherency issue, so maybe
> your backtraces will look different since you're on an AMD CPU - mine is
> Intel), otherwise your best bet probably is to use an UP kernel, or an
> i386 install, interestingly there kqemu works also with SMP.  (well or
> disable kqemu of course.)
>  Oh, another reason for my weird backtraces might be the minidump race,
> and if I read the commitlogs right it is not actually fixed (I obtained
> my dumps before it was discovered), the patches only made sure not to
> write over the end of swap.  So maybe I should try again with minidumps
> disabled (if thats possible), one of these days...
>  Sorry,
> 	Juergen

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