Re: [PATCH] tests/migration: Print some debug on bad status

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

Hi Jens,
  the unplug failover stuff is triggering an assertion occasionally on
aarch64; but
  a) I'm not sure the right way to fix it
  b) And I'm out for a little over a week

so...

* no-reply@patchew.org (no-reply@patchew.org) wrote:
> Patchew URL: https://patchew.org/QEMU/20191108104307.125020-1-dgilbert@redhat.com/
> 
> 
> 
> Hi,
> 
> This series failed the docker-quick@centos7 build test. Please find the testing commands and
> their output below. If you have Docker installed, you can probably reproduce it
> locally.
> 
> === TEST SCRIPT BEGIN ===
> #!/bin/bash
> make docker-image-centos7 V=1 NETWORK=1
> time make docker-test-quick@centos7 SHOW_ENV=1 J=14 NETWORK=1
> === TEST SCRIPT END ===
> 
>   TEST    check-unit: tests/test-bdrv-drain
> wait_for_migration_fail: unexpected status status=wait-unplug allow_active=1

In tests/migration-test.c we've got wait_for_migration_fail, and it's
expecting the state to be any one of:
   setup, failed or maybe active

but it's getting surprised by seeing a 'wait-unplug'

So the question is should we see a wait-unplug?

the migration code has:

    if (qemu_savevm_nr_failover_devices()) {
        migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
                          MIGRATION_STATUS_WAIT_UNPLUG);

Should qemu_savevm_nr_failover_devices() be true?
On aarch64 it seems to have a virtio-net device by default
and qemu_savevm_nr_failover_devices() checks for devices
having dev_unplug_pending but doesn't call it.

I see two fixes but am not sure which is right:
   a) Add 'wait-unplug' to the wait_for_migration_fail
      (easy)
   b) Actually call dev_unplug_pending in qemu_savevm_nr_failover_devices
      so that on a guest which has a virtio-net, but no failover device,
      the state isn't entered.

I think (b) is better, since we shouldn't be exposing the wait-unplug
event on setups that don't expect it; but I don't understand the unplug
enough to know if this is a safe change.

Thoughts?

Dave

--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK