[Virtio-fs] xfstest results for virtio-fs on aarch64

[Stefan Hajnoczi]

On Wed, Oct 16, 2019 at 03:21:52AM +0900, Chirantan Ekbote wrote:
> On Wed, Oct 16, 2019 at 2:28 AM Boeuf, Sebastien
> <sebastien.boeuf at intel.com> wrote:
> >
> > Thanks Dave for adding me to the loop here!
> >
> > On Tue, 2019-10-15 at 17:26 +0100, Dr. David Alan Gilbert wrote:
> > > * Chirantan Ekbote (chirantan at chromium.org) wrote:
> > > > On Wed, Oct 16, 2019 at 12:58 AM Dr. David Alan Gilbert
> > > > <dgilbert at redhat.com> wrote:
> > > > > * Chirantan Ekbote (chirantan at chromium.org) wrote:
> > > > > > I'm not using virtiofsd.  We have our own server for crosvm,
> > > > > > which
> > > > > > supports multiple queues.
> > > > >
> > > > > Ah excellent; is that public anywhere?
> > > > >
> > > >
> > > > It's currently under review here:
> > > > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1758103
> > > >
> > > > I expect to have it merged sometime this week.
> >
> > Oh that's very nice to hear. We have some code from the cloud-
> > hypervisor project where we have a vhost-user-net implementation
> > relying on some sort of a wrapper code similar to what all vhost-user
> > daemon implementations would reuse (libvhost-user kind of thing).
> >
> > We're planning to see this wrapper code land on Rust-VMM at some point,
> > which is why it would be interesting if you could rebase this virtio-fs
> > daemon code on top of this small library. If you don't have the
> > bandwidth, we could probably look at it if that's something you would
> > be interested in.
> >
> > Here is the code for the small wrapper crate:
> > https://github.com/intel/cloud-hypervisor/blob/master/vhost_user_backend/src/lib.rs
> >
> > And here is the vhost-user-net example using it:
> > https://github.com/intel/cloud-hypervisor/blob/master/src/bin/vhost_user_net.rs
> >
> 
> Our virtio-fs server is not a vhost-user device (this was one of the
> reasons we didn't want to use virtiofsd).  It currently just runs
> directly as a child process of crosvm (like all other crosvm devices).
> So unless I'm missing something I don't think there's much to be
> gained by rebasing on vhost_user_backend.

I'm also interested in porting the server over to vhost-user so that
other VMMs like QEMU and cloud-hypervisor can use it.

From a quick look at the code last night, here are things that were not
carried over from virtiofsd:
 * DAX is not supported
 * The FUSE protocol version is a bit dated, e.g. copy_file_range() is
   not supported.
 * Requests are processed synchronously for each virtqueue and therefore
   performance is limited.  The server won't saturate the queue depth
   supported by the host kernel and hardware.

Have I missed anything?  Otherwise it looks quite close to
passthrough_ll.c.

Stefan
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