Re: [PATCH v7 3/5] migration: Add zero-copy parameter for QMP/HMP for Linux

[Leonardo Bras Soares Passos]

Hello Peter,

On Thu, Jan 13, 2022 at 4:00 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Thu, Jan 06, 2022 at 07:13:40PM -0300, Leonardo Bras wrote:
> > Add property that allows zero-copy migration of memory pages,
> > and also includes a helper function migrate_use_zero_copy() to check
> > if it's enabled.
> >
> > No code is introduced to actually do the migration, but it allow
> > future implementations to enable/disable this feature.
> >
> > On non-Linux builds this parameter is compiled-out.
>
> I feel sad every time seeing a new parameter needs to be mostly duplicated 3
> times in the code. :(
>
> > diff --git a/migration/socket.c b/migration/socket.c
> > index 05705a32d8..f7a77aafd3 100644
> > --- a/migration/socket.c
> > +++ b/migration/socket.c
> > @@ -77,6 +77,11 @@ static void socket_outgoing_migration(QIOTask *task,
> >      } else {
> >          trace_migration_socket_outgoing_connected(data->hostname);
> >      }
> > +
> > +    if (migrate_use_zero_copy()) {
> > +        error_setg(&err, "Zero copy not available in migration");
> > +    }
>
> I got confused the 1st time looking at it..  I think this is not strongly
> needed, but that's okay:

The idea is to avoid some future issues on testing migration while bisecting.

>
> Reviewed-by: Peter Xu <peterx@redhat.com>

Thanks Peter!

>
> Thanks,
>
> --
> Peter Xu
>