EOLing of qemu machine types

[Serge Hallyn]

Hi,

In order to facilitate the migration of VMs across host releases,
we done two things - we added release-specific machine types (i.e.
pc-i440fx-trusty and soon pc-1.0-precise), and we introduced a
package called ipxe-precise containing the legacy pxe-roms for
14.04.  An open question is how long to maintain both of these.

For ipxe-precise, we are currently planning to only have that
package in 14.04.  The idea is that that once you've migrated a
VM from a precise to a trusty host, you'll need to change the
machine type and reboot pc-i440fx-trusty before next migrating to
a 16.04 host.

Not as clear is how long to maintain, say pc-1.0-precise and
pc-i440fx-trusty.  My thought is that pc-1.0-precise should exist
only through 14.04 (not in utopic), and likewise pc-i440fx-trusty
should only eixst through 16.04.  If you wish to migrate a VM from
a 14.04 host to say 18.04, you'll need to go through a 16.04 host
first and find a time in the next two years to convert the VM to
the 16.04 default machine type.  This will also allow us to make
sure that any ipxe-trusty package, should we need it, only needs
to exist in 16.04.

Does this seem sensible?  Any suggestions/alternatives are
appreciated.

thanks,
-serge