Re: Regression with latest SeaBIOS booting multi-disk root LVs?

[Gerd Hoffmann]

On Mon, Sep 21, 2020 at 03:10:51PM +0200, Stefan Reiter wrote:
> Hi list,
> 
> since SeaBIOS 1.14.0 (QEMU 5.1) VMs with LVM root disks spanning more than
> one PV fail to boot, if only the first is set as bootable. I believe this is
> due to the changes in SeaBIOS only initializing drives marked as 'bootable'
> by QEMU.
> 
> One fix is to mark all disks containing root data as bootable, but existing
> setups will still break on upgrade (where only the disk containing the
> bootloader is marked). This is not ideal.
> 
> Discovered by a user in our bugtracker:
> https://bugzilla.proxmox.com/show_bug.cgi?id=3011
> 
> and verified by installing Ubuntu 20.04 w/ LVM and GRUB on virtio-scsi, then
> expanding the LV to a second disk.
> 
> I found that just reverting SeaBIOS to 1.13.0 makes it work again, same
> guest install, even with QEMU 5.1.
> 
> Is this intended behaviour?

Yes, it is intentional.  Save some memory and speed up boot by not
initializing disks which are not needed.

> Any fix or workaround?

 - Assign a bootindex to all drives needed, as you already figured, or

 - Start qemu with -boot strict=off, or

 - Install guest with a /boot filesystem on a normal partition.  Which
   is IMHO a good idea anyway for robustness reasons, you can use all
   lvm features without worrying whenever grub is able to cope or not.

take care,
  Gerd