Re: [Qemu-devel] [PATCH 2/3] migration: Remove use of old MigrationParams

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

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> 
> >> Forget -b/-i.
> >> 
> >> migration_set_parameter compression_threads 8
> >> 
> >> migrate <foo>
> >> 
> >> We don't use compression_threads at all
> >> 
> >> migrate_set_capability compress
> >> 
> >> migrate <foo>
> >> 
> >> Now, we use compression threads.
> >> 
> >> So, compression_threads parameter is a parameter that is only used when
> >> compress capability is enabled.
> >> 
> >> Same for block migration.  Block_incremental parameter is used only when
> >> block migration capability is setup.  No dependency check needed at all.
> >> 
> >> Or I am losing something obvious here?
> >
> > Ah, you've made up a new rule
> 
> Oops, I thought that was a rule on how things worked O:-)
> 
> >- I don't think it's a bad rule
> > but is it true? Do we always enable a capability before we use a
> > parameter? I don't think so - I think the tls parameters don't have
> > a capability.
> 
> To use tls paramater, we need to use an url with tls, no?
> 
> > My previous rule was just that if it was a bool it was a capability
> > and you can have whatever dependencies you like there - or none.
> 
> Dunno.
> 
> If you think that we can document it (one way or another), I am for it.
> 
> It is really weird that we both thought (reading) the interface that the
> rules are different O:-)

Well I think that's because no one ever defined any rules!  We just
created parameters because we needed something that could take
non-boolean values, but I don't think there's anything more
about the structure of their use that's actually defined.
Similarly, I don't think there's anything defined about the
structure of capabilities.

Dave

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