Re: [Qemu-devel] [PATCH v2 1/2] virtio: add vhost-user-fs base device

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Cornelia Huck (cohuck@redhat.com) wrote:
> On Fri, 23 Aug 2019 18:56:56 +0100
> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> 
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > The virtio-fs virtio device provides shared file system access using
> > the FUSE protocol carried ovew virtio.
> > The actual file server is implemented in an external vhost-user-fs device
> > backend process.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  configure                                   |  13 +
> >  hw/virtio/Makefile.objs                     |   1 +
> >  hw/virtio/vhost-user-fs.c                   | 297 ++++++++++++++++++++
> >  include/hw/virtio/vhost-user-fs.h           |  45 +++
> >  include/standard-headers/linux/virtio_fs.h  |  41 +++
> >  include/standard-headers/linux/virtio_ids.h |   1 +
> >  6 files changed, 398 insertions(+)
> >  create mode 100644 hw/virtio/vhost-user-fs.c
> >  create mode 100644 include/hw/virtio/vhost-user-fs.h
> >  create mode 100644 include/standard-headers/linux/virtio_fs.h
> > 
> 
> > diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> > new file mode 100644
> > index 0000000000..72e270d869
> > --- /dev/null
> > +++ b/hw/virtio/vhost-user-fs.c
> > @@ -0,0 +1,297 @@
> > +/*
> > + * Vhost-user filesystem virtio device
> > + *
> > + * Copyright 2018 Red Hat, Inc.
> 
> Should that be 2018, 2019? (Also for vhost-user-fs.h.)

Will fix.

> > + *
> > + * Authors:
> > + *  Stefan Hajnoczi <stefanha@redhat.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or
> > + * (at your option) any later version.  See the COPYING file in the
> > + * top-level directory.
> > + */
> > +
> 
> (...)

??

> > +static void vuf_start(VirtIODevice *vdev)
> > +{
> > +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> > +    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> > +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> > +    int ret;
> > +    int i;
> > +
> > +    if (!k->set_guest_notifiers) {
> > +        error_report("binding does not support guest notifiers");
> > +        return;
> > +    }
> > +
> > +    ret = vhost_dev_enable_notifiers(&fs->vhost_dev, vdev);
> > +    if (ret < 0) {
> > +        error_report("Error enabling host notifiers: %d", -ret);
> > +        return;
> > +    }
> > +
> > +    ret = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, true);
> > +    if (ret < 0) {
> > +        error_report("Error binding guest notifier: %d", -ret);
> > +        goto err_host_notifiers;
> > +    }
> > +
> > +    fs->vhost_dev.acked_features = vdev->guest_features;
> > +    ret = vhost_dev_start(&fs->vhost_dev, vdev);
> > +    if (ret < 0) {
> > +        error_report("Error starting vhost: %d", -ret);
> > +        goto err_guest_notifiers;
> > +    }
> > +
> > +    /*
> > +     * guest_notifier_mask/pending not used yet, so just unmask
> > +     * everything here.  virtio-pci will do the right thing by
> > +     * enabling/disabling irqfd.
> 
> I still think referring to virtio-pci doing the right thing is not the
> right thing here :) Can you spell out _what_ the right thing actually
> is?

mst: Can you look at this?

This appears to be a chunk of code that's copied into many vhost files;
it's in at least vhost-user.c, vhost-user-blk.c, vhost-scsi-common.c and
vhost-vsock.c - it seemns to go back until at least 2013.

> > +     */
> > +    for (i = 0; i < fs->vhost_dev.nvqs; i++) {
> > +        vhost_virtqueue_mask(&fs->vhost_dev, vdev, i, false);
> > +    }
> > +
> > +    return;
> > +
> > +err_guest_notifiers:
> > +    k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
> > +err_host_notifiers:
> > +    vhost_dev_disable_notifiers(&fs->vhost_dev, vdev);
> > +}
> > +
> 
> (...)
> 
> > diff --git a/include/standard-headers/linux/virtio_fs.h b/include/standard-headers/linux/virtio_fs.h
> > new file mode 100644
> > index 0000000000..00bd7a6fa7
> > --- /dev/null
> > +++ b/include/standard-headers/linux/virtio_fs.h
> 
> This will probably be imported from the Linux source code, right? If
> yes, this should go into a separate patch (and the headers update patch
> probably needs an update.)

OK, will do.

> > @@ -0,0 +1,41 @@
> > +#ifndef _LINUX_VIRTIO_FS_H
> > +#define _LINUX_VIRTIO_FS_H
> > +/* This header is BSD licensed so anyone can use the definitions to implement
> > + * compatible drivers/servers.
> > + *
> > + * Redistribution and use in source and binary forms, with or without
> > + * modification, are permitted provided that the following conditions
> > + * are met:
> > + * 1. Redistributions of source code must retain the above copyright
> > + *    notice, this list of conditions and the following disclaimer.
> > + * 2. Redistributions in binary form must reproduce the above copyright
> > + *    notice, this list of conditions and the following disclaimer in the
> > + *    documentation and/or other materials provided with the distribution.
> > + * 3. Neither the name of IBM nor the names of its contributors
> > + *    may be used to endorse or promote products derived from this software
> > + *    without specific prior written permission.
> > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
> > + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
> > + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
> > + * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
> > + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> > + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
> > + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> > + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
> > + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
> > + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> > + * SUCH DAMAGE. */
> > +#include "standard-headers/linux/types.h"
> > +#include "standard-headers/linux/virtio_ids.h"
> > +#include "standard-headers/linux/virtio_config.h"
> > +#include "standard-headers/linux/virtio_types.h"
> > +
> > +struct virtio_fs_config {
> > +	/* Filesystem name (UTF-8, not NUL-terminated, padded with NULs) */
> > +	uint8_t tag[36];
> > +
> > +	/* Number of request queues */
> > +	uint32_t num_request_queues;
> > +} QEMU_PACKED;
> > +
> > +#endif /* _LINUX_VIRTIO_FS_H */
> > diff --git a/include/standard-headers/linux/virtio_ids.h b/include/standard-headers/linux/virtio_ids.h
> > index 32b2f94d1f..73fc004807 100644
> > --- a/include/standard-headers/linux/virtio_ids.h
> > +++ b/include/standard-headers/linux/virtio_ids.h
> 
> This should also go into that separate patch.

OK.

Dave

> > @@ -43,6 +43,7 @@
> >  #define VIRTIO_ID_INPUT        18 /* virtio input */
> >  #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
> >  #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
> > +#define VIRTIO_ID_FS           26 /* virtio filesystem */
> >  #define VIRTIO_ID_PMEM         27 /* virtio pmem */
> >  
> >  #endif /* _LINUX_VIRTIO_IDS_H */
> 
> Otherwise, looks good to me.
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK