NetBSD guests won't boot with netbsd-9 DOM0

[Pierre Pronchery <khorben%defora.org@localhost>]

		Hi port-xen,

I am currently updating my hypervisors to netbsd-9, and unlike netbsd-8 
(where any xl command would hang) it seems to work fine, at least with 
my non-NetBSD guests.

In the case of NetBSD DOMU guests however, none of my previous (or new) 
guests boot. They all fail with this error: "mbr partition exceeds disk 
size". They work fine with netbsd-7 as hypervisor, including with a 
netbsd-9 DOMU kernel (with the same configuration file). Booting guests 
with a netbsd-8 DOMU kernel does not help.

I have done the math over and over again in fdisk(8) and disklabel(8), 
but saw nothing wrong. I suspect the guest does not see the right volume 
somehow.

Any other idea what might be going on?

For reference:

> Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
>     2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017,
>     2018, 2019 The NetBSD Foundation, Inc.  All rights reserved.
> Copyright (c) 1982, 1986, 1989, 1991, 1993
>     The Regents of the University of California.  All rights reserved.
>
> NetBSD 8.1_STABLE (XEN3_DOMU)
> total memory = 512 MB
> avail memory = 485 MB
> cpu_rng: RDRAND
> running cgd selftest aes-xts-256 aes-xts-512 done
> mainbus0 (root)
> hypervisor0 at mainbus0: Xen version 4.11.2nb0
> vcpu0 at hypervisor0
> vcpu0: Intel(R) Xeon(R) CPU E3-1246 v3 @ 3.50GHz, id 0x306c3
> vcpu0: package 0, core 0, smt 0
> xenbus0 at hypervisor0: Xen Virtual Bus Interface
> xencons0 at hypervisor0: Xen Virtual Console Driver
> xenbus: can't get state for device/suspend/event-channel (2)
> xbd0 at xenbus0 id 51712: Xen Virtual Block Device Interface
> xennet0 at xenbus0 id 0: Xen Virtual Network Interface
> xennet0: MAC address 11:22:33:44:55:66
> balloon0 at xenbus0 id 0: Xen Balloon driver
> balloon0: current reservation: 524288 KiB
> boot device: xbd0
> xennet0: using RX copy mode
> root on xbd0a dumps on xbd0b
> Supported file systems: mfs lfs ext2fs ffs nfs umap procfs overlay null kernfs fdesc union tmpfs smbfs puffs ptyfs ntfs msdos cd9660 coda
> no file system for xbd0 (dev 0x8e00)
> cannot mount root, error = 79
> root device (default xbd0a):     
> dump device (default xbd0b): 
> file system (default generic): 
> root on xbd0a dumps on xbd0b
> Supported file systems: mfs lfs ext2fs ffs nfs umap procfs overlay null kernfs fdesc union tmpfs smbfs puffs ptyfs ntfs msdos cd9660 coda
> no file system for xbd0 (dev 0x8e00)
> cannot mount root, error = 79
> root device (default xbd0a): help
> use one of: xbd0[a-p] xennet0 ddb halt reboot
> root device (default xbd0a): 
> dump device (default xbd0b): help
> use one of: xbd0[a-p] none ddb halt reboot
> dump device (default xbd0b): 
> file system (default generic): help
> use one of: generic lfs ext2fs ffs nfs smbfs ntfs msdos cd9660 coda ddb halt reboot
> file system (default generic): 
> root on xbd0a dumps on xbd0b
> Supported file systems: mfs lfs ext2fs ffs nfs umap procfs overlay null kernfs fdesc union tmpfs smbfs puffs ptyfs ntfs msdos cd9660 coda
> no file system for xbd0 (dev 0x8e00)
> cannot mount root, error = 
Cheers,
--
khorben