On Thu, Mar 26, 2026 at 11:20:14AM -0500, Brent Cook wrote:
> On Thu, Mar 26, 2026 at 8:35 AM Thomas de Grivel <thodg@kmx.io> wrote:
>
> > I could not boot OpenBSD i386 on an amd64 VM, how did you do ?
> >
>
> I mostly just followed the FAQ VMM guide. It was a bit of a struggle
> getting the networking correct. I had some non-typical routing on my host
> box, and it made the NAT recipe not work initially.
>
>
> >
> > On Thu, Mar 26, 2026 at 2:18 PM Alexander Bluhm <bluhm@openbsd.org> wrote:
> > >
> > > On Thu, Mar 26, 2026 at 12:42:41AM -0500, Brent Cook wrote:
> > > > I was trying to sysupgrade -s a 7.8 VMM machine to a 7.9 snapshot, but
> > the
> > > > upgrade hangs on boot, and am not quite sure how to proceed.  Is this
> > > > something that should work?
> > > >
> > > > I can reset the machine and it comes back fine with the old kernel
> > again.
> > > > The host machine is already running a 6.9 snapshot from this week.
> > >
> > > Running OpenBSD i386 as guest in vmm/vmd is quite broken.  Sometimes
> > > it hangs durign boot soemwhere at "scsibus1 at softraid0: 256
> > > targets".  But the hang happens not reliably, sometimes the machine
> > > is runnig fine.  This makes tracking the bug down difficult.
> > >
> > > We made some experiments with various versions of the host system
> > > and the bug is present at least since OpenBSD 7.4.
> > >
> > > bluhm
> >
> >
> That's good to know, that matches what I'm seeing. It is definitely hanging
> reliably at least with the small/install kernel, so I might be able to
> bisect where it's stuck.

FWIW it also hangs the same way on Hyper-V. At least there if you try a few
dozen times, you might get lucky and have it work. This leads me to believe
it's something in the i386 kernel itself or one of the drivers that is causing
this and not vmm/vmd per-se.

A year or so ago, we determined that how you boot the installer makes a
difference but I can't remember what configuration worked. Eg, booting bsd.rd
manually via vmctl start -b, vs booting the cdXX.iso image vs booting the
installXX.img image vs booting bsd.rd from your already-installed image.

One of those worked reliably and the others were hit and miss.

The right way to debug this is to do it in bochs or qemu+gdb stub where you
can break into the machine with a debugger and see what's going on.

FWIW it's number 196 on my to-do list :)

196 openbsd vmm i386 hang on some ramdisks

-ml