[libvirt] ivshmem server

Daniel P. Berrange berrange at redhat.com
Tue Nov 20 18:28:22 UTC 2012

On Tue, Nov 20, 2012 at 01:16:56PM -0500, Andrew Jones wrote:
> This mail is meant to get a discussion started. Please keep me on cc
> for the discussion, as I'm not subscribed to libvir-list.
> ivshmem is an implementation of an inter-VM communication channel.
> Support for this has been in qemu since v0.14.0 and libvirt patches
> have been recently posted[1]. What's still missing is the ivshmem
> server. The ivshmem server is needed when one would like to use
> interrupts with ivshmem. The server manages a set of eventfds
> to send/recv those interrupts. There is currently only one
> implementation of this server that I'm aware of, which is available
> from this git repo [2] in the ivshmem-server directory. My suggestion
> for libvirt is that this code be integrated into libvirt, rather
> than managed by libvirt, for the following reasons
> 1. libvirt should keep track of the socket path in order to build
>    ivshmem's command line anyway.
> 2. the current ivshmem server code is ~300 lines, so it shouldn't be
>    a large integration effort.
> 3. keeping ivhsmem server separate increases the package management
>    that distributions need to do. afaik, it isn't currently packaged
>    for any distribution.
> One concern I have with the git repo [2] is that I don't see any
> license for ivshmem-server. I've cc'ed Cam for his input.

I guess my main question would be how much more, if any, is the
ivshmem-server expected to grow over time ? I wouldn't want to
get into a fork-situation if people are planning to do much more
dev work on the current ivshmem-server code.

NB, if the code is integrated into libvirt, I think it would
still have to run in a separate daemon. The reason is that we
want to ensure that guests remain fully functional, even when
libvirtd is stopped (whether for RPM upgrade, or due to crash)

I've no particular strong opinion either way on your proposal.
On the surface it seems reasonable to me.

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