Re: ddb in domU

["Jonathan A. Kollasch" <jakllsch%kollasch.net@localhost>]

On Tue, Nov 05, 2024 at 09:06:48AM -0500, Greg Troxel wrote:
> I am trying to debug zfs lockups, and using a domU.  I have succeeded in
> provoking a lockup, I think.  I have an 'xl console' open.
> 
> ddb(4) says +++++ will enter ddb on a domU, but that's for a domU kernel
> presumably.   My domU is HVM with GENERIC.  So I can send "break".  But
> I haven't been able to find what to type to send break.
> 
> It is seeming like one needs a kernel option in the domUs kernel, or to
> get hw.cnmagic, or something.

There might not be a way to send a break in xl console; you'll probably
want to set hw.cnmagic with sysctl.conf or a custom kernel with
option CNMAGIC.  See cn_set_magic(9) for encoding, although "+++++" will
work.