From: Brent Cook <busterb@gmail.com>
Subject: Re: Sysupgrade on i386 vmm to current snapshot hangs on boot into upgrade kernel
To: Mike Larkin <mlarkin@nested.page>
Cc: Thomas de Grivel <thodg@kmx.io>, Alexander Bluhm <bluhm@openbsd.org>,  OpenBSD technical list <tech@openbsd.org>
Date: Sun, 29 Mar 2026 20:04:28 -0500

On Fri, Mar 27, 2026 at 10:53 AM Mike Larkin <mlarkin@nested.page> wrote:

> 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.
>

Unfortunately (or fortunately), I built a new test kernel to start debugging
today, but the VM didn't have the updated user space for the pledge changes
(why I was trying to update to a snapshot in the first place), and the
system was basically unusable after that. So I did a reinstall using a
snapshot from today, and it worked perfectly in VMM for install, and now that
is running without issues.

When the next snapshot comes out, I'll try again.


> >
> >
> > >
> > > 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
>