[libvirt PATCH 6/9] qemu: Allow NBD migration over UNIX socket

[Jiri Denemark]

On Tue, Aug 25, 2020 at 16:28:12 +0100, Daniel P. Berrangé wrote:
> On Tue, Aug 25, 2020 at 07:47:12AM +0200, Martin Kletzander wrote:
> > Adds new typed param for migration and uses this as a UNIX socket path that
> > should be used for the NBD part of migration.  And also adds virsh support.
> > 
> > Partially resolves: https://bugzilla.redhat.com/1638889
> > 
> > Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> > ---
> >  docs/manpages/virsh.rst          |   8 +++
> >  include/libvirt/libvirt-domain.h |  12 ++++
> >  src/qemu/qemu_domain.h           |   1 +
> >  src/qemu/qemu_driver.c           |  33 ++++++++--
> >  src/qemu/qemu_migration.c        | 110 ++++++++++++++++++++++---------
> >  src/qemu/qemu_migration.h        |   3 +
> >  src/qemu/qemu_migration_cookie.c |  22 +++++--
> >  src/qemu/qemu_migration_cookie.h |   1 +
> >  tools/virsh-domain.c             |  12 ++++
> >  9 files changed, 160 insertions(+), 42 deletions(-)
> > 
> > diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst
> > index 9187037a5615..75f475eea6ad 100644
> > --- a/docs/manpages/virsh.rst
> > +++ b/docs/manpages/virsh.rst
> > @@ -3113,6 +3113,7 @@ migrate
> >        [--postcopy-bandwidth bandwidth]
> >        [--parallel [--parallel-connections connections]]
> >        [--bandwidth bandwidth] [--tls-destination hostname]
> > +      [--disks-socket socket-path]
> 
> For the primary migration connection we have a proper URI, so we can
> support new schemes without adding new parameters for each one.
> 
> For the NBD connetion we have the "disk port" parameter only, not a
> full URI.
> 
> Adding "disks socket" makes this design mistake worse.
> 
> IMHO we should add a "disks uri" accepting the exact same syntax
> as the migration URI.

Oh yeah, thanks for mentioning this. I originally thought about generic
disks-uri too, but forgot about it when getting back to the review after
lunch :-/

Just beware the migration URI is basically passed through to QEMU, while
we use nbd or nbd+unix URIs for disks when talking to QEMU and we should
not use these in the API. Just tcp:// or unix:// and translate them to
the correct QEMU nbd URI internally.

Jirka