Re: [Qemu-devel] [PATCH 0/3] Add 'inline-fd:' protocol for migration

[Daniel P . Berrangé]

On Fri, Apr 12, 2019 at 12:13:51PM -0500, Eric Blake wrote:
> On 4/12/19 7:20 AM, Yury Kotov wrote:
> > Hi,
> > 
> > I've added 'inline-fd:' proto to simplify migration to/from fd.
> > I thought about modifying the existing 'fd:' proto but I'm not sure it's a
> > good idea to change it's contract.
> > 
> > Existing 'fd:' proto works with previously added fd by getfd or add-fd 
> > commands.
> > If client doesn't want to work with this fd before or after migration then 
> > it's
> > easier to send an fd with the migrate-* command. Also, client shouldn't 
> > maintain
> > this fd.
> 
> While the sentiment of making it easier by having fewer QMP commands
> might be worthwhile, I'm worried about whether this scales. Having just
> a limited set of commands that take an fd over SCM rights, and every
> other command wired to automagically work with existing named fds,
> scales a lot easier than having to teach individual commands how to take
> an fd inline.

Yeah I tend to agree - we use FD passing extensively across QMP/HMP
and all these commands are written to interact with "getfd". I think
it would be a step backwards to introduce a special case with
migration that doesn't use "getfd".

Regards,
Daniel
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