Re: [PULL 22/33] migration: remove the QEMUFileOps 'get_buffer' callback

[Peter Xu]

On Thu, Jun 23, 2022 at 09:47:51AM +0100, Daniel P. Berrangé wrote:
> > Hmm, when I wanted to run the whole bunch of the migration-test again I
> > found that precopy tls test hangs (/x86_64/migration/precopy/unix/tls/psk).
> > Though for this time it also hangs for me even with the master branch, so
> > maybe not anything wrong with this specific pull req but still something
> > needs fixing..
> 
> That pre-existing test has been runnnig by default in CI for a while
> now, under different OS builds, so I'm surprised. Is there anything
> especially unusual / different about your setup that could explain
> why you see hang that we don't get anywhere else ?

TL;DR: I think it's not run in CI?

Please see ufd_version_check(), as when uffd not detected we'll skip the
whole thing.

We really need to apply this patch, soon-ish..

  https://lore.kernel.org/all/20210615175523.439830-2-peterx@redhat.com/

I can easily reproduce the hang on two x86_64 hosts I have, with current
master commit (2b049d2c8dc01de750410f8f1a4eac498c04c723).  Or am I the only
one?

So I think it also means we don't run migration unit tests on non-Linux
OSes for sure because uffd was never there, meanwhile it also requires
(mostly) root privilege even for Linux hosts so if the sysctl knob was not
set properly (on sysctl.unprivileged_userfaultfd=1) the test can be skipped
too.

When I was changing migration code in the past few months (at least after
I'm aware CI was probably not running it), I ran migration-test manually
with root, but that's not ideal...

-- 
Peter Xu