Re: [RFC] VirtFS support on Xen

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: xen-devel-bounces@lists.xen.org [mailto:xen-devel-
> bounces@lists.xen.org] On Behalf Of Wei Liu
> Sent: 22 January 2016 10:51
> To: Bob Liu
> Cc: Xen-devel; Wei Liu; David Vrabel
> Subject: Re: [Xen-devel] [RFC] VirtFS support on Xen
> 
> On Fri, Jan 22, 2016 at 06:45:30PM +0800, Bob Liu wrote:
> > Hi Wei,
> >
> > On 01/21/2016 06:59 PM, Wei Liu wrote:
> > > On Thu, Jan 21, 2016 at 10:50:08AM +0000, David Vrabel wrote:
> > >> On 21/01/16 10:28, Wei Liu wrote:
> > >>> [RFC] VirtFS support on Xen
> > >>>
> > >>> # Introduction
> > >>>
> > >>> QEMU/KVM supports file system passthrough via an interface called
> > >>> VirtFS [0]. VirtFS is in turn implemented with 9pfs protocol [1] and
> > >>> VirtIO transport.
> > >>>
> > >>> Xen used to have its own implementation of file system passthrough
> > >>> called XenFS, but that has been inactive for a few years. The latest
> > >>> update was in 2009 [2].
> > >>>
> > >>> This project aims to add VirtFS support on Xen. This is more
> > >>> sustainable than inventing our own wheel.#
> > >>
> > >> What's the use case for this?  Who wants this feature?
> > >>
> > >
> > > Anyone who wants file system passthrough.  More specifically, VM-
> based
> > > container solutions can share files from host file system.
> > >
> >
> > I'm a bit confused, can't we just use the VirtFS of Qemu?
> > E.g
> > ./configure --with-extra-qemuu-configure-args="--enable-virtfs"
> >
> 
> Yes, in theory you can -- with VirtIO transport. But I'm not sure if
> Virtio has been fixed to work with Xen.  That also means you need QEMU
> emulation, which we don't really need (or want) when running in PV or
> PVH mode.
> 

Is there not scope for:

a) Fixing VirtIO so it does work with Xen?
b) Resurrecting the idea of emulator disaggregation so that we could spawn a QEMU that only serves as a VirtIO backend so that this can be used for PV/PHV guests?

Seems like a better solution that implementing our own 9p transport and backend.

  Paul

> 
> Wei.
> 
> 
> > Thanks,
> > Bob
> >
> > > http://xendevsummit2015.sched.org/event/3WDg/xen-containers-
> better-way-to-run-docker-containers-sainath-grandhi-
> intel?iframe=no&w=&sidebar=yes&bg=no
> > > http://xendevsummit2015.sched.org/event/3X1L/hyper-make-vm-run-
> like-containers-xu-wang-hyper?iframe=no&w=&sidebar=yes&bg=no
> > >
> > > Wei.
> > >
> 
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