Re: [PATCH 2/2] kvm tools: Add virtio-9p

Ingo Molnar
2011-05-17T19:20:58Z

* Sasha Levin <levinsasha928@gmail.com> wrote:

> On Tue, 2011-05-17 at 20:40 +0200, Ingo Molnar wrote:
> > * Sasha Levin <levinsasha928@gmail.com> wrote:
> >
> > > 3. Within the guest, mount the fs:
> > > mount -t 9p -otrans=virtio kvm_9p <local_dir> -oversion=9p2000
> > > This will mount the 9p server to local_dir.
> >
> > Really cool!
>
> Thanks!
>
> > is root-9p possible? I.e. ideally i'd like to have no image at all - just a
> > guest kernel and a directory hierarchy for the guest filesystem.
>
> >From what I can tell, not currently.
>
> 'kvm_9p' isn't created as a device under /dev, it's just a name used
> internally by 9pnet_virtio (and located under sysfs).
>
> I couldn't figure out which params the kernel would expect to boot using
> 9p over virtio (theres no device name to begin with).
>
> I've also couldn't find anything that suggested it's possible to boot
> using virtio-9p as rootfs.

This needs guest kernel support, in form of a small amount of 9p specific
mounting glue code that the guest kernel will run if either a .config option is
set or a boot commandline is specified.

Such a thing already exists for another networked filesystem: NFS, so i would
suggest looking at the CONFIG_ROOT_NFS=y glue in Linux, i think 9p mounting
support would be welcome!

Thanks,

Ingo