Re: [Qemu-devel] [PATCH 3/6] Add vhost-user-backend

[Marc-André Lureau]

Hi

On Fri, Apr 26, 2019 at 12:27 PM Marc-André Lureau
<address@hidden> wrote:
>
> Create a vhost-user-backend object that holds a connection to a
> vhost-user backend (or "slave" process) and can be referenced from
> virtio devices that support it. See later patches for input & gpu
> usage.
>
> Note: a previous iteration of this object made it user-creatable, and
> allowed managed sub-process spawning, but that has been dropped for
> now.
>
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
>  include/sysemu/vhost-user-backend.h |  57 ++++++++
>  backends/vhost-user.c               | 209 ++++++++++++++++++++++++++++
>  MAINTAINERS                         |   2 +
>  backends/Makefile.objs              |   2 +
>  4 files changed, 270 insertions(+)
>  create mode 100644 include/sysemu/vhost-user-backend.h
>  create mode 100644 backends/vhost-user.c
>
> diff --git a/include/sysemu/vhost-user-backend.h 
> b/include/sysemu/vhost-user-backend.h
> new file mode 100644
> index 0000000000..9abf8f06a1
> --- /dev/null
> +++ b/include/sysemu/vhost-user-backend.h
> @@ -0,0 +1,57 @@
> +/*
> + * QEMU vhost-user backend
> + *
> + * Copyright (C) 2018 Red Hat Inc
> + *
> + * Authors:
> + *  Marc-André Lureau <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#ifndef QEMU_VHOST_USER_BACKEND_H
> +#define QEMU_VHOST_USER_BACKEND_H
> +
> +#include "qom/object.h"
> +#include "exec/memory.h"
> +#include "qemu/option.h"
> +#include "qemu/bitmap.h"
> +#include "hw/virtio/vhost.h"
> +#include "hw/virtio/vhost-user.h"
> +#include "chardev/char-fe.h"
> +#include "io/channel.h"
> +
> +#define TYPE_VHOST_USER_BACKEND "vhost-user-backend"
> +#define VHOST_USER_BACKEND(obj) \
> +    OBJECT_CHECK(VhostUserBackend, (obj), TYPE_VHOST_USER_BACKEND)
> +#define VHOST_USER_BACKEND_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(VhostUserBackendClass, (obj), TYPE_VHOST_USER_BACKEND)
> +#define VHOST_USER_BACKEND_CLASS(klass) \
> +    OBJECT_CLASS_CHECK(VhostUserBackendClass, (klass), 
> TYPE_VHOST_USER_BACKEND)
> +
> +typedef struct VhostUserBackend VhostUserBackend;
> +typedef struct VhostUserBackendClass VhostUserBackendClass;
> +
> +struct VhostUserBackendClass {
> +    ObjectClass parent_class;
> +};
> +
> +struct VhostUserBackend {
> +    /* private */
> +    Object parent;
> +
> +    char *chr_name;
> +    CharBackend chr;
> +    VhostUserState vhost_user;
> +    struct vhost_dev dev;
> +    VirtIODevice *vdev;
> +    bool started;
> +    bool completed;
> +};
> +
> +int vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> +                                unsigned nvqs, Error **errp);
> +void vhost_user_backend_start(VhostUserBackend *b);
> +void vhost_user_backend_stop(VhostUserBackend *b);
> +
> +#endif
> diff --git a/backends/vhost-user.c b/backends/vhost-user.c
> new file mode 100644
> index 0000000000..2b055544a7
> --- /dev/null
> +++ b/backends/vhost-user.c
> @@ -0,0 +1,209 @@
> +/*
> + * QEMU vhost-user backend
> + *
> + * Copyright (C) 2018 Red Hat Inc
> + *
> + * Authors:
> + *  Marc-André Lureau <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +
> +#include "qemu/osdep.h"
> +#include "hw/qdev.h"
> +#include "qapi/error.h"
> +#include "qapi/qmp/qerror.h"
> +#include "qemu/error-report.h"
> +#include "qom/object_interfaces.h"
> +#include "sysemu/vhost-user-backend.h"
> +#include "sysemu/kvm.h"
> +#include "io/channel-command.h"
> +#include "hw/virtio/virtio-bus.h"
> +
> +static bool
> +ioeventfd_enabled(void)
> +{
> +    return kvm_enabled() && kvm_eventfds_enabled();
> +}
> +
> +int
> +vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> +                            unsigned nvqs, Error **errp)
> +{
> +    int ret;
> +
> +    assert(!b->vdev && vdev);
> +
> +    if (!ioeventfd_enabled()) {
> +        error_setg(errp, "vhost initialization failed: requires kvm");
> +        return -1;
> +    }
> +
> +    if (!vhost_user_init(&b->vhost_user, &b->chr, errp)) {
> +        return -1;
> +    }
> +
> +    b->vdev = vdev;
> +    b->dev.nvqs = nvqs;
> +    b->dev.vqs = g_new(struct vhost_virtqueue, nvqs);
> +
> +    ret = vhost_dev_init(&b->dev, &b->vhost_user, VHOST_BACKEND_TYPE_USER, 
> 0);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "vhost initialization failed");
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +void
> +vhost_user_backend_start(VhostUserBackend *b)
> +{
> +    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(b->vdev)));
> +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +    int ret, i ;
> +
> +    if (b->started) {
> +        return;
> +    }
> +
> +    if (!k->set_guest_notifiers) {
> +        error_report("binding does not support guest notifiers");
> +        return;
> +    }
> +
> +    ret = vhost_dev_enable_notifiers(&b->dev, b->vdev);
> +    if (ret < 0) {
> +        return;
> +    }
> +
> +    ret = k->set_guest_notifiers(qbus->parent, b->dev.nvqs, true);
> +    if (ret < 0) {
> +        error_report("Error binding guest notifier");
> +        goto err_host_notifiers;
> +    }
> +
> +    b->dev.acked_features = b->vdev->guest_features;
> +    ret = vhost_dev_start(&b->dev, b->vdev);
> +    if (ret < 0) {
> +        error_report("Error start vhost dev");
> +        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 < b->dev.nvqs; i++) {
> +        vhost_virtqueue_mask(&b->dev, b->vdev,
> +                             b->dev.vq_index + i, false);
> +    }
> +
> +    b->started = true;
> +    return;
> +
> +err_guest_notifiers:
> +    k->set_guest_notifiers(qbus->parent, b->dev.nvqs, false);
> +err_host_notifiers:
> +    vhost_dev_disable_notifiers(&b->dev, b->vdev);
> +}
> +
> +void
> +vhost_user_backend_stop(VhostUserBackend *b)
> +{
> +    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(b->vdev)));
> +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +    int ret = 0;
> +
> +    if (!b->started) {
> +        return;
> +    }
> +
> +    vhost_dev_stop(&b->dev, b->vdev);
> +
> +    if (k->set_guest_notifiers) {
> +        ret = k->set_guest_notifiers(qbus->parent,
> +                                     b->dev.nvqs, false);
> +        if (ret < 0) {
> +            error_report("vhost guest notifier cleanup failed: %d", ret);
> +        }
> +    }
> +    assert(ret >= 0);
> +
> +    vhost_dev_disable_notifiers(&b->dev, b->vdev);
> +    b->started = false;
> +}
> +
> +static void set_chardev(Object *obj, const char *value, Error **errp)
> +{
> +    VhostUserBackend *b = VHOST_USER_BACKEND(obj);
> +    Chardev *chr;
> +
> +    if (b->completed) {
> +        error_setg(errp, QERR_PERMISSION_DENIED);
> +        return;
> +    }
> +
> +    g_free(b->chr_name);
> +    b->chr_name = g_strdup(value);
> +
> +    chr = qemu_chr_find(b->chr_name);
> +    if (chr == NULL) {
> +        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
> +                  "Chardev '%s' not found", b->chr_name);
> +        return;
> +    }
> +
> +    if (!qemu_chr_fe_init(&b->chr, chr, errp)) {
> +        return;
> +    }
> +
> +    b->completed = true;
> +    /* could call vhost_dev_init() so early message can be exchanged */
> +}
> +
> +static char *get_chardev(Object *obj, Error **errp)
> +{
> +    VhostUserBackend *b = VHOST_USER_BACKEND(obj);
> +    Chardev *chr = qemu_chr_fe_get_driver(&b->chr);
> +
> +    if (chr && chr->label) {
> +        return g_strdup(chr->label);
> +    }
> +
> +    return NULL;
> +}
> +
> +static void vhost_user_backend_init(Object *obj)
> +{
> +    object_property_add_str(obj, "chardev", get_chardev, set_chardev, NULL);
> +}
> +
> +static void vhost_user_backend_finalize(Object *obj)
> +{
> +    VhostUserBackend *b = VHOST_USER_BACKEND(obj);
> +
> +    g_free(b->dev.vqs);
> +    g_free(b->chr_name);
> +
> +    vhost_user_cleanup(&b->vhost_user);
> +    qemu_chr_fe_deinit(&b->chr, true);
> +}
> +
> +static const TypeInfo vhost_user_backend_info = {
> +    .name = TYPE_VHOST_USER_BACKEND,
> +    .parent = TYPE_OBJECT,
> +    .instance_size = sizeof(VhostUserBackend),
> +    .instance_init = vhost_user_backend_init,
> +    .instance_finalize = vhost_user_backend_finalize,
> +    .class_size = sizeof(VhostUserBackendClass),
> +};
> +
> +static void register_types(void)
> +{
> +    type_register_static(&vhost_user_backend_info);
> +}
> +
> +type_init(register_types);
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 23db6f8408..c48f13f877 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1469,6 +1469,8 @@ F: hw/*/*vhost*
>  F: docs/interop/vhost-user.json
>  F: docs/interop/vhost-user.txt
>  F: contrib/vhost-user-*/
> +F: backends/vhost-user.c
> +F: include/sysemu/vhost-user-backend.h
>
>  virtio
>  M: Michael S. Tsirkin <address@hidden>
> diff --git a/backends/Makefile.objs b/backends/Makefile.objs
> index ff619d31b4..5d9df08552 100644
> --- a/backends/Makefile.objs
> +++ b/backends/Makefile.objs
> @@ -14,4 +14,6 @@ common-obj-y += cryptodev-vhost.o
>  common-obj-$(CONFIG_VHOST_CRYPTO) += cryptodev-vhost-user.o
>  endif
>
> +common-obj-$(CONFIG_VHOST_USER) += vhost-user.o

This should be changed back to "$(call
land,$(CONFIG_VHOST_USER),$(CONFIG_VIRTIO))"

(I wonder if CONFIG_VHOST_USER could depend on CONFIG_VIRTIO somewhere
else though)

> +
>  common-obj-$(CONFIG_LINUX) += hostmem-memfd.o
> --
> 2.21.0.313.ge35b8cb8e2
>
>


-- 
Marc-André Lureau