Re: [PATCH v4 2/3] virtio: add vhost-user-fs base device

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

Hi

On Mon, Sep 30, 2019 at 2:52 PM 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 over 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         | 299 ++++++++++++++++++++++++++++++
>  include/hw/virtio/vhost-user-fs.h |  45 +++++
>  4 files changed, 358 insertions(+)
>  create mode 100644 hw/virtio/vhost-user-fs.c
>  create mode 100644 include/hw/virtio/vhost-user-fs.h
>
> diff --git a/configure b/configure
> index 542f6aea3f..204cbe351e 100755
> --- a/configure
> +++ b/configure
> @@ -381,6 +381,7 @@ vhost_crypto=""
>  vhost_scsi=""
>  vhost_vsock=""
>  vhost_user=""
> +vhost_user_fs=""
>  kvm="no"
>  hax="no"
>  hvf="no"
> @@ -1293,6 +1294,10 @@ for opt do
>    ;;
>    --enable-vhost-vsock) vhost_vsock="yes"
>    ;;
> +  --disable-vhost-user-fs) vhost_user_fs="no"
> +  ;;
> +  --enable-vhost-user-fs) vhost_user_fs="yes"
> +  ;;
>    --disable-opengl) opengl="no"
>    ;;
>    --enable-opengl) opengl="yes"
> @@ -2236,6 +2241,10 @@ test "$vhost_crypto" = "" && vhost_crypto=$vhost_user
>  if test "$vhost_crypto" = "yes" && test "$vhost_user" = "no"; then
>    error_exit "--enable-vhost-crypto requires --enable-vhost-user"
>  fi
> +test "$vhost_user_fs" = "" && vhost_user_fs=$vhost_user
> +if test "$vhost_user_fs" = "yes" && test "$vhost_user" = "no"; then
> +  error_exit "--enable-vhost-user-fs requires --enable-vhost-user"
> +fi
>
>  # OR the vhost-kernel and vhost-user values for simplicity
>  if test "$vhost_net" = ""; then
> @@ -6377,6 +6386,7 @@ echo "vhost-crypto support $vhost_crypto"
>  echo "vhost-scsi support $vhost_scsi"
>  echo "vhost-vsock support $vhost_vsock"
>  echo "vhost-user support $vhost_user"
> +echo "vhost-user-fs support $vhost_user_fs"
>  echo "Trace backends    $trace_backends"
>  if have_backend "simple"; then
>  echo "Trace output file $trace_file-<pid>"
> @@ -6873,6 +6883,9 @@ fi
>  if test "$vhost_user" = "yes" ; then
>    echo "CONFIG_VHOST_USER=y" >> $config_host_mak
>  fi
> +if test "$vhost_user_fs" = "yes" ; then
> +  echo "CONFIG_VHOST_USER_FS=y" >> $config_host_mak
> +fi
>  if test "$blobs" = "yes" ; then
>    echo "INSTALL_BLOBS=yes" >> $config_host_mak
>  fi
> diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
> index 964ce78607..47ffbf22c4 100644
> --- a/hw/virtio/Makefile.objs
> +++ b/hw/virtio/Makefile.objs
> @@ -11,6 +11,7 @@ common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
>  common-obj-$(CONFIG_VIRTIO_MMIO) += virtio-mmio.o
>  obj-$(CONFIG_VIRTIO_BALLOON) += virtio-balloon.o
>  obj-$(CONFIG_VIRTIO_CRYPTO) += virtio-crypto.o
> +obj-$(CONFIG_VHOST_USER_FS) += vhost-user-fs.o
>  obj-$(call land,$(CONFIG_VIRTIO_CRYPTO),$(CONFIG_VIRTIO_PCI)) += virtio-crypto-pci.o
>  obj-$(CONFIG_VIRTIO_PMEM) += virtio-pmem.o
>  common-obj-$(call land,$(CONFIG_VIRTIO_PMEM),$(CONFIG_VIRTIO_PCI)) += virtio-pmem-pci.o
> diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> new file mode 100644
> index 0000000000..f0df7f4746
> --- /dev/null
> +++ b/hw/virtio/vhost-user-fs.c
> @@ -0,0 +1,299 @@
> +/*
> + * Vhost-user filesystem virtio device
> + *
> + * Copyright 2018-2019 Red Hat, Inc.
> + *
> + * 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.
> + */
> +
> +#include "qemu/osdep.h"
> +#include <sys/ioctl.h>
> +#include "standard-headers/linux/virtio_fs.h"
> +#include "qapi/error.h"
> +#include "hw/qdev-properties.h"
> +#include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/virtio-access.h"
> +#include "qemu/error-report.h"
> +#include "hw/virtio/vhost-user-fs.h"
> +#include "monitor/monitor.h"
> +
> +static void vuf_get_config(VirtIODevice *vdev, uint8_t *config)
> +{
> +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> +    struct virtio_fs_config fscfg = {};
> +
> +    memcpy((char *)fscfg.tag, fs->conf.tag,
> +           MIN(strlen(fs->conf.tag) + 1, sizeof(fscfg.tag)));
> +
> +    virtio_stl_p(vdev, &fscfg.num_request_queues, fs->conf.num_request_queues);
> +
> +    memcpy(config, &fscfg, sizeof(fscfg));
> +}
> +
> +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.
> +     */
> +    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);
> +}
> +
> +static void vuf_stop(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;
> +
> +    if (!k->set_guest_notifiers) {
> +        return;
> +    }
> +
> +    vhost_dev_stop(&fs->vhost_dev, vdev);
> +
> +    ret = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
> +    if (ret < 0) {
> +        error_report("vhost guest notifier cleanup failed: %d", ret);
> +        return;
> +    }
> +
> +    vhost_dev_disable_notifiers(&fs->vhost_dev, vdev);
> +}
> +
> +static void vuf_set_status(VirtIODevice *vdev, uint8_t status)
> +{
> +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> +    bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK;
> +
> +    if (!vdev->vm_running) {
> +        should_start = false;
> +    }
> +
> +    if (fs->vhost_dev.started == should_start) {
> +        return;
> +    }
> +
> +    if (should_start) {
> +        vuf_start(vdev);
> +    } else {
> +        vuf_stop(vdev);
> +    }
> +}

It looks like you could have benefited from backends/vhost-user.c

This would allow to factor out some common code and properties used by
vhost-user devices (currently gpu & input, but more could be
converted).

Advantage is that if we add a new mechanism, say to start helpers
(like I propose earlier), all devices using that could benefit it more
easily (in theory).

> +
> +static uint64_t vuf_get_features(VirtIODevice *vdev,
> +                                      uint64_t requested_features,
> +                                      Error **errp)
> +{
> +    /* No feature bits used yet */
> +    return requested_features;
> +}
> +
> +static void vuf_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    /*
> +     * Not normally called; it's the daemon that handles the queue;
> +     * however virtio's cleanup path can call this.
> +     */
> +}
> +
> +static void vuf_guest_notifier_mask(VirtIODevice *vdev, int idx,
> +                                            bool mask)
> +{
> +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> +
> +    vhost_virtqueue_mask(&fs->vhost_dev, vdev, idx, mask);
> +}
> +
> +static bool vuf_guest_notifier_pending(VirtIODevice *vdev, int idx)
> +{
> +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> +
> +    return vhost_virtqueue_pending(&fs->vhost_dev, idx);
> +}
> +
> +static void vuf_device_realize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VHostUserFS *fs = VHOST_USER_FS(dev);
> +    unsigned int i;
> +    size_t len;
> +    int ret;
> +
> +    if (!fs->conf.chardev.chr) {
> +        error_setg(errp, "missing chardev");
> +        return;
> +    }
> +
> +    if (!fs->conf.tag) {
> +        error_setg(errp, "missing tag property");
> +        return;
> +    }
> +    len = strlen(fs->conf.tag);
> +    if (len == 0) {
> +        error_setg(errp, "tag property cannot be empty");
> +        return;
> +    }
> +    if (len > sizeof_field(struct virtio_fs_config, tag)) {
> +        error_setg(errp, "tag property must be %zu bytes or less",
> +                   sizeof_field(struct virtio_fs_config, tag));
> +        return;
> +    }
> +
> +    if (fs->conf.num_request_queues == 0) {
> +        error_setg(errp, "num-request-queues property must be larger than 0");
> +        return;
> +    }
> +
> +    if (!is_power_of_2(fs->conf.queue_size)) {
> +        error_setg(errp, "queue-size property must be a power of 2");
> +        return;
> +    }
> +
> +    if (fs->conf.queue_size > VIRTQUEUE_MAX_SIZE) {
> +        error_setg(errp, "queue-size property must be %u or smaller",
> +                   VIRTQUEUE_MAX_SIZE);
> +        return;
> +    }
> +
> +    if (!vhost_user_init(&fs->vhost_user, &fs->conf.chardev, errp)) {
> +        return;
> +    }
> +
> +    virtio_init(vdev, "vhost-user-fs", VIRTIO_ID_FS,
> +                sizeof(struct virtio_fs_config));
> +
> +    /* Hiprio queue */
> +    virtio_add_queue(vdev, fs->conf.queue_size, vuf_handle_output);
> +
> +    /* Request queues */
> +    for (i = 0; i < fs->conf.num_request_queues; i++) {
> +        virtio_add_queue(vdev, fs->conf.queue_size, vuf_handle_output);
> +    }
> +
> +    /* 1 high prio queue, plus the number configured */
> +    fs->vhost_dev.nvqs = 1 + fs->conf.num_request_queues;
> +    fs->vhost_dev.vqs = g_new0(struct vhost_virtqueue, fs->vhost_dev.nvqs);
> +    ret = vhost_dev_init(&fs->vhost_dev, &fs->vhost_user,
> +                         VHOST_BACKEND_TYPE_USER, 0);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "vhost_dev_init failed");
> +        goto err_virtio;
> +    }
> +
> +    return;
> +
> +err_virtio:
> +    vhost_user_cleanup(&fs->vhost_user);
> +    virtio_cleanup(vdev);
> +    g_free(fs->vhost_dev.vqs);
> +    return;
> +}
> +
> +static void vuf_device_unrealize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VHostUserFS *fs = VHOST_USER_FS(dev);
> +
> +    /* This will stop vhost backend if appropriate. */
> +    vuf_set_status(vdev, 0);
> +
> +    vhost_dev_cleanup(&fs->vhost_dev);
> +
> +    vhost_user_cleanup(&fs->vhost_user);
> +
> +    virtio_cleanup(vdev);
> +    g_free(fs->vhost_dev.vqs);
> +    fs->vhost_dev.vqs = NULL;
> +}
> +
> +static const VMStateDescription vuf_vmstate = {
> +    .name = "vhost-user-fs",
> +    .unmigratable = 1,
> +};
> +
> +static Property vuf_properties[] = {
> +    DEFINE_PROP_CHR("chardev", VHostUserFS, conf.chardev),
> +    DEFINE_PROP_STRING("tag", VHostUserFS, conf.tag),
> +    DEFINE_PROP_UINT16("num-request-queues", VHostUserFS,
> +                       conf.num_request_queues, 1),
> +    DEFINE_PROP_UINT16("queue-size", VHostUserFS, conf.queue_size, 128),
> +    DEFINE_PROP_STRING("vhostfd", VHostUserFS, conf.vhostfd),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void vuf_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> +
> +    dc->props = vuf_properties;
> +    dc->vmsd = &vuf_vmstate;
> +    set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
> +    vdc->realize = vuf_device_realize;
> +    vdc->unrealize = vuf_device_unrealize;
> +    vdc->get_features = vuf_get_features;
> +    vdc->get_config = vuf_get_config;
> +    vdc->set_status = vuf_set_status;
> +    vdc->guest_notifier_mask = vuf_guest_notifier_mask;
> +    vdc->guest_notifier_pending = vuf_guest_notifier_pending;
> +}
> +
> +static const TypeInfo vuf_info = {
> +    .name = TYPE_VHOST_USER_FS,
> +    .parent = TYPE_VIRTIO_DEVICE,
> +    .instance_size = sizeof(VHostUserFS),
> +    .class_init = vuf_class_init,
> +};
> +
> +static void vuf_register_types(void)
> +{
> +    type_register_static(&vuf_info);
> +}
> +
> +type_init(vuf_register_types)
> diff --git a/include/hw/virtio/vhost-user-fs.h b/include/hw/virtio/vhost-user-fs.h
> new file mode 100644
> index 0000000000..539885b458
> --- /dev/null
> +++ b/include/hw/virtio/vhost-user-fs.h
> @@ -0,0 +1,45 @@
> +/*
> + * Vhost-user filesystem virtio device
> + *
> + * Copyright 2018-2019 Red Hat, Inc.
> + *
> + * 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.
> + */
> +
> +#ifndef _QEMU_VHOST_USER_FS_H
> +#define _QEMU_VHOST_USER_FS_H
> +
> +#include "hw/virtio/virtio.h"
> +#include "hw/virtio/vhost.h"
> +#include "hw/virtio/vhost-user.h"
> +#include "chardev/char-fe.h"
> +
> +#define TYPE_VHOST_USER_FS "vhost-user-fs-device"
> +#define VHOST_USER_FS(obj) \
> +        OBJECT_CHECK(VHostUserFS, (obj), TYPE_VHOST_USER_FS)
> +
> +typedef struct {
> +    CharBackend chardev;
> +    char *tag;
> +    uint16_t num_request_queues;
> +    uint16_t queue_size;
> +    char *vhostfd;
> +} VHostUserFSConf;
> +
> +typedef struct {
> +    /*< private >*/
> +    VirtIODevice parent;
> +    VHostUserFSConf conf;
> +    struct vhost_virtqueue *vhost_vqs;
> +    struct vhost_dev vhost_dev;
> +    VhostUserState vhost_user;
> +
> +    /*< public >*/
> +} VHostUserFS;
> +
> +#endif /* _QEMU_VHOST_USER_FS_H */
> --
> 2.21.0
>
>


-- 
Marc-André Lureau