[GEDI] [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling

[Daniel P. Berrangé]

On Tue, May 07, 2024 at 06:52:50AM +0200, Jinpu Wang wrote:
> Hi Peter, hi Daniel,
> On Mon, May 6, 2024 at 5:29 PM Peter Xu <peterx at redhat.com> wrote:
> >
> > On Mon, May 06, 2024 at 12:08:43PM +0200, Jinpu Wang wrote:
> > > Hi Peter, hi Daniel,
> >
> > Hi, Jinpu,
> >
> > Thanks for sharing this test results.  Sounds like a great news.
> >
> > What's your plan next?  Would it then be worthwhile / possible moving QEMU
> > into that direction?  Would that greatly simplify rdma code as Dan
> > mentioned?
> I'm rather not familiar with QEMU migration yet,  from the test
> result, I think it's a possible direction,
> just we need to at least based on a rather recent release like
> rdma-core v33 with proper 'fork' support.
> 
> Maybe Dan or you could give more detail about what you have in mind
> for using rsocket as a replacement for the future.
> We will also look into the implementation details in the meantime.

The migration/socket.c file is the entrypoint for traditional TCP
based migration code. It uses the QIOChannelSocket class which is
written against the traditional sockets APIs, and uses the QAPI
SocketAddress data type to configure it..

My thought was that potentially SocketAddress could be extended to
offer RDMA addressing eg


{ 'union': 'SocketAddress',
  'base': { 'type': 'SocketAddressType' },
  'discriminator': 'type',
  'data': { 'inet': 'InetSocketAddress',
            'unix': 'UnixSocketAddress',
            'vsock': 'VsockSocketAddress',
            'fd': 'FdSocketAddress',
	    'rdma': 'InetSocketAddress' } }

And then QIOChannelSocket could be also extended to call the
alternative 'rsockets' APIs where needed. That would mean that
existing sockets migration code would almost "just work" with
RDMA. Theoreticaly any other part of QEMU using QIOChannelSocket
would also then magically support RDMA too, with very little (if
any) extra work.

With regards,
Daniel
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