[Virtio-fs] [PATCH v3 07/20] virtio: add vhost-user-base and a generic vhost-user-device
Matias Ezequiel Vara Larsen
mvaralar at redhat.com
Tue Sep 5 14:19:15 UTC 2023
On Mon, Jul 10, 2023 at 04:35:09PM +0100, Alex Bennée wrote:
> In theory we shouldn't need to repeat so much boilerplate to support
> vhost-user backends. This provides a generic vhost-user-base QOM
> object and a derived vhost-user-device for which the user needs to
> provide the few bits of information that aren't currently provided by
> the vhost-user protocol. This should provide a baseline implementation
> from which the other vhost-user stub can specialise.
>
> Signed-off-by: Alex Bennée <alex.bennee at linaro.org>
>
> ---
> v2
> - split into vub and vud
> ---
> include/hw/virtio/vhost-user-device.h | 45 ++++
> hw/virtio/vhost-user-device.c | 324 ++++++++++++++++++++++++++
> hw/virtio/meson.build | 2 +
> 3 files changed, 371 insertions(+)
> create mode 100644 include/hw/virtio/vhost-user-device.h
> create mode 100644 hw/virtio/vhost-user-device.c
>
> diff --git a/include/hw/virtio/vhost-user-device.h b/include/hw/virtio/vhost-user-device.h
> new file mode 100644
> index 0000000000..9105011e25
> --- /dev/null
> +++ b/include/hw/virtio/vhost-user-device.h
> @@ -0,0 +1,45 @@
> +/*
> + * Vhost-user generic virtio device
> + *
> + * Copyright (c) 2023 Linaro Ltd
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef QEMU_VHOST_USER_DEVICE_H
> +#define QEMU_VHOST_USER_DEVICE_H
> +
> +#include "hw/virtio/vhost.h"
> +#include "hw/virtio/vhost-user.h"
> +
> +#define TYPE_VHOST_USER_BASE "vhost-user-base"
> +
> +OBJECT_DECLARE_TYPE(VHostUserBase, VHostUserBaseClass, VHOST_USER_BASE)
> +
> +struct VHostUserBase {
> + VirtIODevice parent;
> + /* Properties */
> + CharBackend chardev;
> + uint16_t virtio_id;
> + uint32_t num_vqs;
> + /* State tracking */
> + VhostUserState vhost_user;
> + struct vhost_virtqueue *vhost_vq;
> + struct vhost_dev vhost_dev;
> + GPtrArray *vqs;
> + bool connected;
> +};
> +
> + /* needed so we can use the base realize after specialisation
> + tweaks */
> +struct VHostUserBaseClass {
> + /*< private >*/
> + VirtioDeviceClass parent_class;
> + /*< public >*/
> + DeviceRealize parent_realize;
> +};
> +
> +/* shared for the benefit of the derived pci class */
> +#define TYPE_VHOST_USER_DEVICE "vhost-user-device"
> +
> +#endif /* QEMU_VHOST_USER_DEVICE_H */
> diff --git a/hw/virtio/vhost-user-device.c b/hw/virtio/vhost-user-device.c
> new file mode 100644
> index 0000000000..b0239fa033
> --- /dev/null
> +++ b/hw/virtio/vhost-user-device.c
> @@ -0,0 +1,324 @@
> +/*
> + * Generic vhost-user stub. This can be used to connect to any
> + * vhost-user backend. All configuration details must be handled by
> + * the vhost-user daemon itself
> + *
> + * Copyright (c) 2023 Linaro Ltd
> + * Author: Alex Bennée <alex.bennee at linaro.org>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "hw/qdev-properties.h"
> +#include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/vhost-user-device.h"
> +#include "qemu/error-report.h"
> +
> +static void vub_start(VirtIODevice *vdev)
> +{
> + BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> + VHostUserBase *vub = VHOST_USER_BASE(vdev);
> + int ret, i;
> +
> + if (!k->set_guest_notifiers) {
> + error_report("binding does not support guest notifiers");
> + return;
> + }
> +
> + ret = vhost_dev_enable_notifiers(&vub->vhost_dev, vdev);
> + if (ret < 0) {
> + error_report("Error enabling host notifiers: %d", -ret);
> + return;
> + }
> +
> + ret = k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, true);
> + if (ret < 0) {
> + error_report("Error binding guest notifier: %d", -ret);
> + goto err_host_notifiers;
> + }
> +
> + vub->vhost_dev.acked_features = vdev->guest_features;
> +
> + ret = vhost_dev_start(&vub->vhost_dev, vdev, true);
> + if (ret < 0) {
> + error_report("Error starting vhost-user-device: %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 < vub->vhost_dev.nvqs; i++) {
> + vhost_virtqueue_mask(&vub->vhost_dev, vdev, i, false);
> + }
> +
> + return;
> +
> +err_guest_notifiers:
> + k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, false);
> +err_host_notifiers:
> + vhost_dev_disable_notifiers(&vub->vhost_dev, vdev);
> +}
> +
> +static void vub_stop(VirtIODevice *vdev)
> +{
> + VHostUserBase *vub = VHOST_USER_BASE(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(&vub->vhost_dev, vdev, true);
> +
> + ret = k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, false);
> + if (ret < 0) {
> + error_report("vhost guest notifier cleanup failed: %d", ret);
> + return;
> + }
> +
> + vhost_dev_disable_notifiers(&vub->vhost_dev, vdev);
> +}
> +
> +static void vub_set_status(VirtIODevice *vdev, uint8_t status)
> +{
> + VHostUserBase *vub = VHOST_USER_BASE(vdev);
> + bool should_start = virtio_device_should_start(vdev, status);
> +
> + if (vhost_dev_is_started(&vub->vhost_dev) == should_start) {
> + return;
> + }
> +
> + if (should_start) {
> + vub_start(vdev);
> + } else {
> + vub_stop(vdev);
> + }
> +}
> +
> +/*
> + * For an implementation where everything is delegated to the backend
> + * we don't do anything other than return the full feature set offered
> + * by the daemon (module the reserved feature bit).
> + */
> +static uint64_t vub_get_features(VirtIODevice *vdev,
> + uint64_t requested_features, Error **errp)
> +{
> + VHostUserBase *vub = VHOST_USER_BASE(vdev);
> + /* This should be set when the vhost connection initialises */
> + g_assert(vub->vhost_dev.features);
> + return vub->vhost_dev.features & ~(1ULL << VHOST_USER_F_PROTOCOL_FEATURES);
> +}
> +
> +static void vub_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 do_vhost_user_cleanup(VirtIODevice *vdev, VHostUserBase *vub)
> +{
> + vhost_user_cleanup(&vub->vhost_user);
> +
> + for (int i = 0; i < vub->num_vqs; i++) {
> + VirtQueue *vq = g_ptr_array_index(vub->vqs, i);
> + virtio_delete_queue(vq);
> + }
> +
> + virtio_cleanup(vdev);
> +}
> +
> +static int vub_connect(DeviceState *dev)
> +{
> + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> + VHostUserBase *vub = VHOST_USER_BASE(vdev);
> +
> + if (vub->connected) {
> + return 0;
> + }
> + vub->connected = true;
> +
> + /* restore vhost state */
> + if (virtio_device_started(vdev, vdev->status)) {
> + vub_start(vdev);
> + }
> +
> + return 0;
> +}
> +
> +static void vub_disconnect(DeviceState *dev)
> +{
> + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> + VHostUserBase *vub = VHOST_USER_BASE(vdev);
> +
> + if (!vub->connected) {
> + return;
> + }
> + vub->connected = false;
> +
> + if (vhost_dev_is_started(&vub->vhost_dev)) {
> + vub_stop(vdev);
> + }
> +}
> +
> +static void vub_event(void *opaque, QEMUChrEvent event)
> +{
> + DeviceState *dev = opaque;
> + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> + VHostUserBase *vub = VHOST_USER_BASE(vdev);
> +
> + switch (event) {
> + case CHR_EVENT_OPENED:
> + if (vub_connect(dev) < 0) {
> + qemu_chr_fe_disconnect(&vub->chardev);
> + return;
> + }
> + break;
> + case CHR_EVENT_CLOSED:
> + vub_disconnect(dev);
> + break;
> + case CHR_EVENT_BREAK:
> + case CHR_EVENT_MUX_IN:
> + case CHR_EVENT_MUX_OUT:
> + /* Ignore */
> + break;
> + }
> +}
> +
> +static void vub_device_realize(DeviceState *dev, Error **errp)
> +{
> + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> + VHostUserBase *vub = VHOST_USER_BASE(dev);
> + int ret;
> +
> + if (!vub->chardev.chr) {
> + error_setg(errp, "vhost-user-device: missing chardev");
> + return;
> + }
> +
> + if (!vub->virtio_id) {
> + error_setg(errp, "vhost-user-device: need to define device id");
> + return;
> + }
> +
> + if (!vub->num_vqs) {
> + vub->num_vqs = 1; /* reasonable default? */
> + }
> +
> + if (!vhost_user_init(&vub->vhost_user, &vub->chardev, errp)) {
> + return;
> + }
> +
> + virtio_init(vdev, vub->virtio_id, 0);
> +
> + /*
> + * Disable guest notifiers, by default all notifications will be via the
> + * asynchronous vhost-user socket.
> + */
> + vdev->use_guest_notifier_mask = false;
> +
> + /* Allocate queues */
> + vub->vqs = g_ptr_array_sized_new(vub->num_vqs);
> + for (int i = 0; i < vub->num_vqs; i++) {
> + g_ptr_array_add(vub->vqs,
> + virtio_add_queue(vdev, 4, vub_handle_output));
> + }
> +
Hello Alex, apologies if someone already asked this. If I understand
correctly, the second parameter of virtio_add_queue() is the len of the
queue. Why have you chosen "4" as its value? Shall qemu query the len of
the queue from the vhost-user device instead?
Matias
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