Re: [Xen-devel] [Xen Hackathon] new PV drivers

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-06-09 at 10:42 +0100, Stefano Stabellini wrote:
> On Mon, 9 Jun 2014, Ian Campbell wrote:
> > On Fri, 2014-06-06 at 14:56 +0100, Anil Madhavapeddy wrote:
> > > On 3 Jun 2014, at 12:47, Stefano Stabellini 
> > > <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > > 
> > > > Present (by memory):
> > > > - Julien Grall,
> > > > - Stefano Stabellini,
> > > > - Ian Campbell,
> > > > - Roger Pau Monne,
> > > > - Dario Faggioli,
> > > > - Andrii Tseglytskyi,
> > > > - David Vrabel,
> > > > - Konrad Wilk.
> > > > 
> > > > * What new PV devices do we need? What has been done already?
> > > 
> > > I missed this session, but was wondering about an entropy driver.
> > > We're integrating an OCaml SSL/TLS into MirageOS, and it's not clear
> > > how PV guests should go about getting a strong source of entropy from
> > > the outside world in a reasonably portable way.
> > > 
> > > VirtIO has a RNG [1] -- has anyone got any interest in a PV protocol
> > > for Xen that does the same?
> > 
> > IMHO support for these sorts of things is actually one of the few good
> > reasons to be considering support for basic virtio on Xen.
> > 
> > Alternatively AIUI a bunch of these sort of virtio devices are just
> > protocols built on top of virtio_serial, so we could perhaps be thinking
> > of repurposing them over Xen's serial PV device. Dave S was
> > investigating the difference between libvirt "serial" and "channel"
> > recently and AIUI the difference was that a channel could be named in
> > order to support bindings to these higher level things (i.e. appearing
> > to the guest as /dev/rng instead of /dev/hvcN).
> 
> However writing a good PV-RNG should be far easier than making virtio
> work properly with Xen PV guests.

True. I was mostly thinking about the trivial ones which didn't need
zero copy/DMA which might have made it simpler.

In any case as I said I think most of the interesting little ones are
actually based on the virtio-serial so making them work over xen PV
console channels should be pretty easy.

Ian.


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