Re: [PATCH v3 00/11] tests/migration-test: Allow testing older machine types

[Fabiano Rosas]

Fabiano Rosas <farosas@suse.de> writes:

> This adds support for running migration-test with two different QEMU
> versions to test migration compatibility. The tests automatically
> choose the latest machine type supported by both QEMU versions.

Let me point out two situations that came up while developing this:

1) There was a generic command line change in QEMU (-audio option)
   introduced this cycle that was ported to the command line used by
   libqtest.c. This means that when using the same command line to
   start both guests, the older one will not recognize the option and
   will break.

   Ideally, we would keep command lines out of the library and require
   each test to provide their own. Then maybe the migration code could
   cope with the change somehow.

2) When fixing an issue during a release cycle, that issue can still
   show up on the next one when using this series to test
   compatibility. There's probably not much we can do here, but
   remember the issues that were already fixed and ignore them when
   they appear in these compatibiliy tests.

I don't see how to avoid the situations above, but I think their
existence implies we cannot enable by default any sort of migration
compatibility testing that uses a live guest.