Panic compiling qemu under amd64

[Julio Merino <jmmv%julipedia.org@localhost>]

Hello,

I thought I'd draw some attention to PR kern/45361 by asking
current-users if anyone else can experience this problem.  It has been
showing up here for a few weeks already (IIRC) with a stock GENERIC kernel.

I can consistently crash my amd64 virtual machine by compiling qemu.
The crash typically happens when building the intel-hda.c file, although
the crash exposes itself in many different ways.  Sometimes, the machine
just locks up.  Other times, it shows a stacktrace involving kevent1().
 And at least one time, the stacktrace was related to vmem_alloc().
(See the bug report for the full stack traces.)

The kernel I'm running now has LOCKDEBUG enabled in an attempt to get
some extra information out of the lock ups, but this does not seem to
have helped.  I'm building qemu with options "-sdl" if that matters.

All my attempts to investigate the crash by using the core dump in
/var/crash have been futile.  Either the core dump is corrupt or gdb
cannot really extract any useful data out of them...

Can anyone reproduce these crashes?

Thanks.