Re: [Qemu-devel] Towards an ivshmem 2.0?

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Mon, Jan 16, 2017 at 02:10:17PM +0100, Jan Kiszka wrote:
> On 2017-01-16 13:41, Marc-André Lureau wrote:
> > On Mon, Jan 16, 2017 at 12:37 PM Jan Kiszka <jan.kiszka@siemens.com
> > <mailto:jan.kiszka@siemens.com>> wrote:
> >     So, this is our proposal. Would be great to hear some opinions if you
> >     see value in adding support for such an "ivshmem 2.0" device to QEMU as
> >     well and expand its ecosystem towards Linux upstream, maybe also DPDK
> >     again. If you see problems in the new design /wrt what QEMU provides so
> >     far with its ivshmem device, let's discuss how to resolve them. Looking
> >     forward to any feedback!
> > 
> > 
> > My feeling is that ivshmem is not being actively developped in qemu, but
> > rather virtio-based solutions (vhost-pci for vm2vm).
> 
> As pointed out, for us it's most important to keep the design simple -
> even at the price of "reinventing" some drivers for upstream (at least,
> we do not need two sets of drivers because our interface is fully
> symmetric). I don't see yet how vhost-pci could achieve the same, but
> I'm open to learn more!

The concept of symmetry is nice but only applies for communications
channels like networking and serial.

It doesn't apply for I/O that is fundamentally asymmetric like disk I/O.

I just wanted to point this out because lack symmetry has also bothered
me about virtio but it's actually impossible to achieve it for all
device types.

Stefan

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