Re: [Qemu-devel] [PATCH] migrate: Migration aborts abruptly for machine "none"

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

* Daniel P. Berrange (berrange@redhat.com) wrote:
> On Thu, Jan 26, 2017 at 02:46:52PM +0530, Ashijeet Acharya wrote:
> > Migration of a "none" machine with no RAM crashes abruptly as
> > bitmap_new() fails and thus aborts. Instead, place a check for
> > last_ram_offset() being '0' at the start of ram_save_setup() and
> > error out with a meaningful error message.
> > 
> > Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> > ---
> >  migration/ram.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/migration/ram.c b/migration/ram.c
> > index ef8fadf..bf05d69 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -1947,6 +1947,11 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> >  {
> >      RAMBlock *block;
> >  
> > +    if (last_ram_offset() == 0) {
> > +        error_report("Failed to migrate: No RAM available!");
> > +        return -1;
> > +    }
> > +
> 
> If we're merely going to block migration, as opposed to making it work,
> then IMHO we should use migration blockers registered at machine setup
> for this task.
> 
> We have a new cli arg added to QEMU to tell it to abort startup if the
> machine configuration is not migratable. That only works if using
> migration blockers - this check you've added is too late to be detected
> at startup.

Hmm, yes you're right, that would be better.
Although it does lead to an interesting situation where starting with a 'none'
and constructing it component at a time would get rejected by --only-migratable
even though the final construction is fine.

Dave

> 
> Regards,
> Daniel
> -- 
> |: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
> |: http://libvirt.org              -o-             http://virt-manager.org :|
> |: http://entangle-photo.org       -o-    http://search.cpan.org/~danberr/ :|
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK