Recent versions of pxeboot hang/panic on AMD platform.

[Luigi Rizzo]

On Fri, Nov 21, 2008 at 03:23:25PM -0800, Andrew Thompson wrote:
> On Sat, Nov 22, 2008 at 12:14:00AM +0100, Luigi Rizzo wrote:
> > [copying some people involved with recent related commits]
> > 
> > As reported in  kern/118222 recent versions of pxeboot hang/panic
> > on AMD platform.
> > 
> > Initial reports mentioned that the RELENG_6 versions worked well,
> > however i found out that even the recent RELENG_6 code is problematic.
> > 
> > Specifically, the problem i see on two machines with AMD CPU (one
> > is an Asus M2N-VM) motherboard netbooting with PXEboot, is that the
> > loading of config files or binary modules (kernel, etc.) randomly
> > hangs with recent version of pxeboot (RELENG_6, RELENG_7 and HEAD
> > all give the same behaviour).
> 
> I have found that the kernel size can trigger this for me, after
> reducing the size I didnt experience loader hangs with pxe. You may want
> to experiment with this in your investigations.

no luck - the hang often occurs as early as while reading loader.conf,
which is way smaller than the kernel.

Assuming that the interrupt thing is a possible cause for the bug,
I can understand that the kernel size can affect the probability of
getting an interrupt at the wrong time.

There was one bug due to memory overflow that i fixed in a recent
commit to head (see boot/common/interp.c),
but this only helped on a different amd64 motherboard.

cheers
luigi