Re: [Qemu-devel] [RFC PATCH RDMA support v4: 09/10] check for QMP string and bypass nonblock() calls

[Michael R. Hines]

On 03/19/2013 05:23 AM, Paolo Bonzini wrote:
> Yes---this is a separate patch.  Apologies if you had the if(fd != -1)
> before. :)  In fact, both the if(fd != -1) and the
> if(!migrate_use_rdma(f)) are bad, but I prefer to eliminate as many uses
> as possible of migrate_use_rdma.
I agree. In my current patch I've eliminated all of them.

> Does librdmacm support non-blocking operation, similar to select() or
> poll()?  Perhaps we can add support for that later.

Yes, it does, actually. The library provides what is called an "event 
channel".
(This term is overloaded by other technologies, but that's OK).

An event channel is a file descriptor provided by (I believe) the rdma_cm
kernel module driver.

When you poll on this file descriptor, it can tell you all sorts of things
just like other files or sockets like when data is ready or when
events of interest have completed (like the completion queue has elements).

In my current patch, I'm using this during 
"rdma_accept_incoming_connection()",
but I'm not currently using it for the rest of the coroutine on the 
receiver side.