Re: [Xen-devel] [RFC] VirtFS support on Xen

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Sat, Jan 23, 2016 at 01:33:40PM +0800, Bob Liu wrote:
> 
> On 01/22/2016 06:50 PM, Wei Liu wrote:
> > 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.
> > 
> 
> Just make sure if I get it right, in the KVM case:
> Linux guest(v9fs-client) -> VirtIO transport -> Qemu(v9fs-server) -> Local 
> file system in Host
> 
> And your plan is:
> DomU(v9fs-client) -> XEN transport:grant map based -> Qemu(v9fs-server) -> 
> Local file system in Dom0
> 

Yes. Your understanding is correct.

> Which means we need to implement a XEN-transport in linux/net/9p/, and also 
> make Qemu can recognize this transport because we need Qemu to run as the 
> v9fs-server anyway?
> 

Yes. There will be code in both QEMU and Linux kernel.

Wei.

> Bob

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