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

[Cornelia Huck]

On Fri, 23 Aug 2019 18:56:56 +0100
"Dr. David Alan Gilbert (git)" <address@hidden> wrote:

> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> 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 <address@hidden>
> Signed-off-by: Sebastien Boeuf <address@hidden>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  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.)

> + *
> + * Authors:
> + *  Stefan Hajnoczi <address@hidden>
> + *
> + * 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?

> +     */
> +    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.)

> @@ -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.

> @@ -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.