Re: [Qemu-devel] [PATCH v3 2/2] docs: update ivshmem device spec

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Fri, Aug 08, 2014 at 10:55:18AM +0200, David Marchand wrote:
> +For each client (QEMU processes) that connects to the server:
> +- the server assigns an ID for this client and sends this ID to him as the first
> +  message,
> +- the server sends a fd to the shared memory object to this client,
> +- the server creates a new set of host eventfds associated to the new client and
> +  sends this set to all already connected clients,
> +- finally, the server sends all the eventfds sets for all clients to the new
> +  client.

The protocol is not extensible and no version number is exchanged.  For
the most part this should be okay because clients must run on the same
machine as the server.  It is assumed clients and server are compatible
with each other.

I wonder if we'll get into trouble later if the protocol needs to be
extended or some operation needs to happen, like upgrading QEMU or the
ivshmem-server.  At the very least someone building from source but
using system QEMU or ivshmem-server could get confusing failures if the
protocol doesn't match.

How about sending a version message as the first thing during a
connection?

Stefan

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