[libvirt] [PATCHv6 5/6] bhyve: Add console support for grub-bhyve bootloader

[Roman Bogorodskiy]

  Conrad Meyer wrote:

> This enables booting interactive GRUB menus (e.g. install CDs) with
> libvirt-bhyve.
> 
> Caveat: A terminal other than the '--console' option to 'virsh start'
> (e.g. 'cu -l /dev/nmdm0B -s 115200') must be used to connect to
> grub-bhyve because the bhyve loader path is synchronous and must occur
> before the VM actually starts.
> 
> Changing the bhyveProcessStart logic around to accommodate '--console'
> for interactive loader use seems like a significant project and probably
> not worth it, if UEFI/BIOS support for bhyve is "coming soon."

I'm still feeling doubtful about this part. I see the impact of this
change in the following way.

 * Users, who wish to use console with grub-bhyve:
   - They still cannot use 'virsh console' for that and need to use 'cu'
     or something like that
   - They need to update to a specific grub-bhyve version (currently
     unreleased). The information about required version is not very
     easy to find, so the chance is high that most users will miss it

 * Users, who doesn't need to use console with grub-bhyve:
   - They will still need to update to the specific grub-bhyve version,
     otherwise a domain with bhyve-grub bootloader will fail with not
     very obvious from user's POV error because of the unknown argument
     to grub-bhyve

If we leave the thing as is, e.g. only have bootloader support, then we
will have:

 * Users, who with to use console with grub-bhyve:
   - Have to construct bootloader_args manually to add the --cons-dev 
   argument
   - Like in a case with an explicit support, cannot use 'virsh console'
     for the bootloader step
   - Obviously, need to update grub-bhyve

 * users, who doesn't need to use console with grub-bhyve
   - Nothing changes for them, they can use an older grub-bhyve without
     issues

Roman Bogorodskiy