Re: [PATCH 2/3] vhost-blk: Add vhost-blk-common abstraction

[Raphael Norwitz <raphael.norwitz@nutanix.com>]

I'm mostly happy with this. Just some asks on variable renaming and
comments which need to be fixed because of how you've moved things
around.

Also let's add a MAINTAINERS entry vhost-blk-common.h/c either under
vhost-user-blk or create a new vhost-blk entry. I'm not sure what the
best practices are for this. 

On Thu, Apr 08, 2021 at 06:12:51PM +0800, Xie Yongji wrote:
> This commit abstracts part of vhost-user-blk into a common
> parent class which is useful for the introducation of vhost-vdpa-blk.
> 
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
>  hw/block/meson.build                 |   2 +-
>  hw/block/vhost-blk-common.c          | 291 +++++++++++++++++++++++++
>  hw/block/vhost-user-blk.c            | 306 +++++----------------------
>  hw/virtio/vhost-user-blk-pci.c       |   7 +-
>  include/hw/virtio/vhost-blk-common.h |  50 +++++
>  include/hw/virtio/vhost-user-blk.h   |  20 +-
>  6 files changed, 396 insertions(+), 280 deletions(-)
>  create mode 100644 hw/block/vhost-blk-common.c
>  create mode 100644 include/hw/virtio/vhost-blk-common.h
> 
> diff --git a/hw/block/meson.build b/hw/block/meson.build
> index 5b4a7699f9..5862bda4cb 100644
> --- a/hw/block/meson.build
> +++ b/hw/block/meson.build
> @@ -16,6 +16,6 @@ softmmu_ss.add(when: 'CONFIG_TC58128', if_true: files('tc58128.c'))
>  softmmu_ss.add(when: 'CONFIG_NVME_PCI', if_true: files('nvme.c', 'nvme-ns.c', 'nvme-subsys.c', 'nvme-dif.c'))
>  
>  specific_ss.add(when: 'CONFIG_VIRTIO_BLK', if_true: files('virtio-blk.c'))
> -specific_ss.add(when: 'CONFIG_VHOST_USER_BLK', if_true: files('vhost-user-blk.c'))
> +specific_ss.add(when: 'CONFIG_VHOST_USER_BLK', if_true: files('vhost-blk-common.c', 'vhost-user-blk.c'))
>  
>  subdir('dataplane')
> diff --git a/hw/block/vhost-blk-common.c b/hw/block/vhost-blk-common.c
> new file mode 100644
> index 0000000000..96500f6c89
> --- /dev/null
> +++ b/hw/block/vhost-blk-common.c
> @@ -0,0 +1,291 @@
> +/*
> + * Parent class for vhost based block devices
> + *
> + * Copyright (C) 2021 Bytedance Inc. and/or its affiliates. All rights reserved.
> + *
> + * Author:
> + *   Xie Yongji <xieyongji@bytedance.com>
> + *
> + * Heavily based on the vhost-user-blk.c by:
> + *   Changpeng Liu <changpeng.liu@intel.com>

You should probably also give credit to Felipe, Setfan and Nicholas, as
a lot of vhost-user-blk orignally came from their work.

> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qemu/error-report.h"
> +#include "qemu/cutils.h"
> +#include "hw/qdev-core.h"
> +#include "hw/qdev-properties.h"
> +#include "hw/qdev-properties-system.h"
> +#include "hw/virtio/vhost.h"
> +#include "hw/virtio/virtio.h"
> +#include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/virtio-access.h"
> +#include "hw/virtio/vhost-blk-common.h"
> +#include "sysemu/sysemu.h"
> +#include "sysemu/runstate.h"
> +
> +static void vhost_blk_common_update_config(VirtIODevice *vdev, uint8_t *config)
> +{
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(vdev);
> +
> +    /* Our num_queues overrides the device backend */
> +    virtio_stw_p(vdev, &vbc->blkcfg.num_queues, vbc->num_queues);
> +
> +    memcpy(config, &vbc->blkcfg, sizeof(struct virtio_blk_config));
> +}
> +
> +static void vhost_blk_common_set_config(VirtIODevice *vdev,
> +                                        const uint8_t *config)
> +{
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(vdev);
> +    struct virtio_blk_config *blkcfg = (struct virtio_blk_config *)config;
> +    int ret;
> +
> +    if (blkcfg->wce == vbc->blkcfg.wce) {
> +        return;
> +    }
> +
> +    ret = vhost_dev_set_config(&vbc->dev, &blkcfg->wce,
> +                               offsetof(struct virtio_blk_config, wce),
> +                               sizeof(blkcfg->wce),
> +                               VHOST_SET_CONFIG_TYPE_MASTER);
> +    if (ret) {
> +        error_report("set device config space failed");
> +        return;
> +    }
> +
> +    vbc->blkcfg.wce = blkcfg->wce;
> +}
> +
> +static int vhost_blk_common_handle_config_change(struct vhost_dev *dev)
> +{
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(dev->vdev);
> +    struct virtio_blk_config blkcfg;
> +    int ret;
> +
> +    ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg,
> +                               sizeof(struct virtio_blk_config));
> +    if (ret < 0) {
> +        error_report("get config space failed");
> +        return ret;
> +    }
> +
> +    /* valid for resize only */
> +    if (blkcfg.capacity != vbc->blkcfg.capacity) {
> +        vbc->blkcfg.capacity = blkcfg.capacity;
> +        memcpy(dev->vdev->config, &vbc->blkcfg,
> +               sizeof(struct virtio_blk_config));
> +        virtio_notify_config(dev->vdev);
> +    }
> +
> +    return 0;
> +}
> +
> +const VhostDevConfigOps blk_ops = {
> +    .vhost_dev_config_notifier = vhost_blk_common_handle_config_change,
> +};
> +
> +static uint64_t vhost_blk_common_get_features(VirtIODevice *vdev,
> +                                              uint64_t features,
> +                                              Error **errp)
> +{
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(vdev);
> +
> +    /* Turn on pre-defined features */
> +    virtio_add_feature(&features, VIRTIO_BLK_F_SEG_MAX);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_FLUSH);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_RO);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_DISCARD);
> +    virtio_add_feature(&features, VIRTIO_BLK_F_WRITE_ZEROES);
> +
> +    if (vbc->config_wce) {
> +        virtio_add_feature(&features, VIRTIO_BLK_F_CONFIG_WCE);
> +    }
> +    if (vbc->num_queues > 1) {
> +        virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
> +    }
> +
> +    return vhost_get_features(&vbc->dev, vbc->feature_bits, features);
> +}
> +
> +int vhost_blk_common_start(VHostBlkCommon *vbc)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(vbc);
> +    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +    int i, ret;
> +
> +    if (!k->set_guest_notifiers) {
> +        error_report("binding does not support guest notifiers");
> +        return -ENOSYS;
> +    }
> +
> +    ret = vhost_dev_enable_notifiers(&vbc->dev, vdev);
> +    if (ret < 0) {
> +        error_report("Error enabling host notifiers: %d", -ret);
> +        return ret;
> +    }
> +
> +    ret = k->set_guest_notifiers(qbus->parent, vbc->dev.nvqs, true);
> +    if (ret < 0) {
> +        error_report("Error binding guest notifier: %d", -ret);
> +        goto err_host_notifiers;
> +    }
> +
> +    vbc->dev.acked_features = vdev->guest_features;
> +
> +    ret = vhost_dev_prepare_inflight(&vbc->dev, vdev);
> +    if (ret < 0) {
> +        error_report("Error set inflight format: %d", -ret);
> +        goto err_guest_notifiers;
> +    }
> +
> +    if (!vbc->inflight->addr) {
> +        ret = vhost_dev_get_inflight(&vbc->dev, vbc->queue_size, vbc->inflight);
> +        if (ret < 0) {
> +            error_report("Error get inflight: %d", -ret);
> +            goto err_guest_notifiers;
> +        }
> +    }
> +
> +    ret = vhost_dev_set_inflight(&vbc->dev, vbc->inflight);
> +    if (ret < 0) {
> +        error_report("Error set inflight: %d", -ret);
> +        goto err_guest_notifiers;
> +    }
> +
> +    ret = vhost_dev_start(&vbc->dev, vdev);
> +    if (ret < 0) {
> +        error_report("Error starting vhost: %d", -ret);
> +        goto err_guest_notifiers;
> +    }

I think this will create confusion with vhost_dev->started, which is why
I wanted it named started_vu. Can we change this to started_vbc or
something like that?

> +    vbc->started = true;
> +
> +    /* 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 < vbc->dev.nvqs; i++) {
> +        vhost_virtqueue_mask(&vbc->dev, vdev, i, false);
> +    }
> +
> +    return ret;
> +
> +err_guest_notifiers:
> +    k->set_guest_notifiers(qbus->parent, vbc->dev.nvqs, false);
> +err_host_notifiers:
> +    vhost_dev_disable_notifiers(&vbc->dev, vdev);
> +    return ret;
> +}
> +
> +void vhost_blk_common_stop(VHostBlkCommon *vbc)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(vbc);
> +    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +    int ret;
> +
> +    if (!vbc->started) {
> +        return;
> +    }
> +    vbc->started = false;
> +
> +    if (!k->set_guest_notifiers) {
> +        return;
> +    }
> +
> +    vhost_dev_stop(&vbc->dev, vdev);
> +
> +    ret = k->set_guest_notifiers(qbus->parent, vbc->dev.nvqs, false);
> +    if (ret < 0) {
> +        error_report("vhost guest notifier cleanup failed: %d", ret);
> +        return;
> +    }
> +
> +    vhost_dev_disable_notifiers(&vbc->dev, vdev);
> +}
> +
> +void vhost_blk_common_realize(VHostBlkCommon *vbc,
> +                              VirtIOHandleOutput handle_output,
> +                              Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(vbc);
> +    int i;
> +
> +    if (vbc->num_queues == VHOST_BLK_AUTO_NUM_QUEUES) {
> +        vbc->num_queues = 1;
> +    }
> +
> +    if (!vbc->num_queues || vbc->num_queues > VIRTIO_QUEUE_MAX) {
> +        error_setg(errp, "vhost-blk-common: invalid number of IO queues");
> +        return;
> +    }
> +
> +    if (!vbc->queue_size) {
> +        error_setg(errp, "vhost-blk-common: queue size must be non-zero");
> +        return;
> +    }
> +
> +    virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK,
> +                sizeof(struct virtio_blk_config));
> +
> +    vbc->virtqs = g_new(VirtQueue *, vbc->num_queues);
> +    for (i = 0; i < vbc->num_queues; i++) {
> +        vbc->virtqs[i] = virtio_add_queue(vdev, vbc->queue_size,
> +                                          handle_output);
> +    }
> +
> +    vbc->inflight = g_new0(struct vhost_inflight, 1);
> +    vbc->vhost_vqs = g_new0(struct vhost_virtqueue, vbc->num_queues);
> +}
> +
> +void vhost_blk_common_unrealize(VHostBlkCommon *vbc)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(vbc);
> +    int i;
> +
> +    g_free(vbc->vhost_vqs);
> +    vbc->vhost_vqs = NULL;
> +    g_free(vbc->inflight);
> +    vbc->inflight = NULL;
> +
> +    for (i = 0; i < vbc->num_queues; i++) {
> +        virtio_delete_queue(vbc->virtqs[i]);
> +    }
> +    g_free(vbc->virtqs);
> +    virtio_cleanup(vdev);
> +}
> +
> +static void vhost_blk_common_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> +
> +    set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
> +    vdc->get_config = vhost_blk_common_update_config;
> +    vdc->set_config = vhost_blk_common_set_config;
> +    vdc->get_features = vhost_blk_common_get_features;
> +}
> +
> +static const TypeInfo vhost_blk_common_info = {
> +    .name = TYPE_VHOST_BLK_COMMON,
> +    .parent = TYPE_VIRTIO_DEVICE,
> +    .instance_size = sizeof(VHostBlkCommon),
> +    .class_init = vhost_blk_common_class_init,
> +    .abstract = true,
> +};
> +
> +static void virtio_register_types(void)
> +{
> +    type_register_static(&vhost_blk_common_info);
> +}
> +
> +type_init(virtio_register_types)
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 0b5b9d44cd..0ad2cc030a 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -50,165 +50,10 @@ static const int user_feature_bits[] = {
>      VHOST_INVALID_FEATURE_BIT
>  };
>  
> -static void vhost_user_blk_update_config(VirtIODevice *vdev, uint8_t *config)
> -{
> -    VHostUserBlk *s = VHOST_USER_BLK(vdev);
> -
> -    /* Our num_queues overrides the device backend */
> -    virtio_stw_p(vdev, &s->blkcfg.num_queues, s->num_queues);
> -
> -    memcpy(config, &s->blkcfg, sizeof(struct virtio_blk_config));
> -}
> -
> -static void vhost_user_blk_set_config(VirtIODevice *vdev, const uint8_t *config)
> -{
> -    VHostUserBlk *s = VHOST_USER_BLK(vdev);
> -    struct virtio_blk_config *blkcfg = (struct virtio_blk_config *)config;
> -    int ret;
> -
> -    if (blkcfg->wce == s->blkcfg.wce) {
> -        return;
> -    }
> -
> -    ret = vhost_dev_set_config(&s->dev, &blkcfg->wce,
> -                               offsetof(struct virtio_blk_config, wce),
> -                               sizeof(blkcfg->wce),
> -                               VHOST_SET_CONFIG_TYPE_MASTER);
> -    if (ret) {
> -        error_report("set device config space failed");
> -        return;
> -    }
> -
> -    s->blkcfg.wce = blkcfg->wce;
> -}
> -
> -static int vhost_user_blk_handle_config_change(struct vhost_dev *dev)
> -{
> -    int ret;
> -    struct virtio_blk_config blkcfg;
> -    VHostUserBlk *s = VHOST_USER_BLK(dev->vdev);
> -
> -    ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg,
> -                               sizeof(struct virtio_blk_config));
> -    if (ret < 0) {
> -        error_report("get config space failed");
> -        return -1;
> -    }
> -
> -    /* valid for resize only */
> -    if (blkcfg.capacity != s->blkcfg.capacity) {
> -        s->blkcfg.capacity = blkcfg.capacity;
> -        memcpy(dev->vdev->config, &s->blkcfg, sizeof(struct virtio_blk_config));
> -        virtio_notify_config(dev->vdev);
> -    }
> -
> -    return 0;
> -}
> -
> -const VhostDevConfigOps blk_ops = {
> -    .vhost_dev_config_notifier = vhost_user_blk_handle_config_change,
> -};
> -
> -static int vhost_user_blk_start(VirtIODevice *vdev)
> -{
> -    VHostUserBlk *s = VHOST_USER_BLK(vdev);
> -    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> -    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> -    int i, ret;
> -
> -    if (!k->set_guest_notifiers) {
> -        error_report("binding does not support guest notifiers");
> -        return -ENOSYS;
> -    }
> -
> -    ret = vhost_dev_enable_notifiers(&s->dev, vdev);
> -    if (ret < 0) {
> -        error_report("Error enabling host notifiers: %d", -ret);
> -        return ret;
> -    }
> -
> -    ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, true);
> -    if (ret < 0) {
> -        error_report("Error binding guest notifier: %d", -ret);
> -        goto err_host_notifiers;
> -    }
> -
> -    s->dev.acked_features = vdev->guest_features;
> -
> -    ret = vhost_dev_prepare_inflight(&s->dev, vdev);
> -    if (ret < 0) {
> -        error_report("Error set inflight format: %d", -ret);
> -        goto err_guest_notifiers;
> -    }
> -
> -    if (!s->inflight->addr) {
> -        ret = vhost_dev_get_inflight(&s->dev, s->queue_size, s->inflight);
> -        if (ret < 0) {
> -            error_report("Error get inflight: %d", -ret);
> -            goto err_guest_notifiers;
> -        }
> -    }
> -
> -    ret = vhost_dev_set_inflight(&s->dev, s->inflight);
> -    if (ret < 0) {
> -        error_report("Error set inflight: %d", -ret);
> -        goto err_guest_notifiers;
> -    }
> -
> -    ret = vhost_dev_start(&s->dev, vdev);
> -    if (ret < 0) {
> -        error_report("Error starting vhost: %d", -ret);
> -        goto err_guest_notifiers;
> -    }
> -    s->started_vu = true;
> -
> -    /* 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 < s->dev.nvqs; i++) {
> -        vhost_virtqueue_mask(&s->dev, vdev, i, false);
> -    }
> -
> -    return ret;
> -
> -err_guest_notifiers:
> -    k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
> -err_host_notifiers:
> -    vhost_dev_disable_notifiers(&s->dev, vdev);
> -    return ret;
> -}
> -
> -static void vhost_user_blk_stop(VirtIODevice *vdev)
> -{
> -    VHostUserBlk *s = VHOST_USER_BLK(vdev);
> -    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> -    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> -    int ret;
> -
> -    if (!s->started_vu) {
> -        return;
> -    }
> -    s->started_vu = false;
> -
> -    if (!k->set_guest_notifiers) {
> -        return;
> -    }
> -
> -    vhost_dev_stop(&s->dev, vdev);
> -
> -    ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
> -    if (ret < 0) {
> -        error_report("vhost guest notifier cleanup failed: %d", ret);
> -        return;
> -    }
> -
> -    vhost_dev_disable_notifiers(&s->dev, vdev);
> -}
> -
>  static void vhost_user_blk_set_status(VirtIODevice *vdev, uint8_t status)
>  {
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>      bool should_start = virtio_device_started(vdev, status);
>      int ret;
>  
> @@ -220,52 +65,27 @@ static void vhost_user_blk_set_status(VirtIODevice *vdev, uint8_t status)
>          return;
>      }
>  
> -    if (s->dev.started == should_start) {
> +    if (vbc->dev.started == should_start) {
>          return;
>      }
>  
>      if (should_start) {
> -        ret = vhost_user_blk_start(vdev);
> +        ret = vhost_blk_common_start(vbc);
>          if (ret < 0) {
>              error_report("vhost-user-blk: vhost start failed: %s",
>                           strerror(-ret));
>              qemu_chr_fe_disconnect(&s->chardev);
>          }
>      } else {
> -        vhost_user_blk_stop(vdev);
> +        vhost_blk_common_stop(vbc);
>      }
>  
>  }
>  
> -static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,
> -                                            uint64_t features,
> -                                            Error **errp)
> -{
> -    VHostUserBlk *s = VHOST_USER_BLK(vdev);
> -
> -    /* Turn on pre-defined features */
> -    virtio_add_feature(&features, VIRTIO_BLK_F_SEG_MAX);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_FLUSH);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_RO);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_DISCARD);
> -    virtio_add_feature(&features, VIRTIO_BLK_F_WRITE_ZEROES);
> -
> -    if (s->config_wce) {
> -        virtio_add_feature(&features, VIRTIO_BLK_F_CONFIG_WCE);
> -    }
> -    if (s->num_queues > 1) {
> -        virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
> -    }
> -
> -    return vhost_get_features(&s->dev, user_feature_bits, features);
> -}
> -
>  static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>  {
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>      int i, ret;
>  
>      if (!vdev->start_on_kick) {
> @@ -276,14 +96,14 @@ static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>          return;
>      }
>  
> -    if (s->dev.started) {
> +    if (vbc->dev.started) {
>          return;
>      }
>  
>      /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
>       * vhost here instead of waiting for .set_status().
>       */
> -    ret = vhost_user_blk_start(vdev);
> +    ret = vhost_blk_common_start(vbc);
>      if (ret < 0) {
>          error_report("vhost-user-blk: vhost start failed: %s",
>                       strerror(-ret));
> @@ -292,7 +112,7 @@ static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>      }
>  
>      /* Kick right away to begin processing requests already in vring */
> -    for (i = 0; i < s->dev.nvqs; i++) {
> +    for (i = 0; i < vbc->dev.nvqs; i++) {
>          VirtQueue *kick_vq = virtio_get_queue(vdev, i);
>  
>          if (!virtio_queue_get_desc_addr(vdev, i)) {
> @@ -305,14 +125,16 @@ static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>  static void vhost_user_blk_reset(VirtIODevice *vdev)
>  {
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>  
> -    vhost_dev_free_inflight(s->inflight);
> +    vhost_dev_free_inflight(vbc->inflight);
>  }
>  
>  static int vhost_user_blk_connect(DeviceState *dev)
>  {
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>      int ret = 0;
>  
>      if (s->connected) {
> @@ -320,14 +142,15 @@ static int vhost_user_blk_connect(DeviceState *dev)
>      }
>      s->connected = true;
>  
> -    s->dev.nvqs = s->num_queues;
> -    s->dev.vqs = s->vhost_vqs;
> -    s->dev.vq_index = 0;
> -    s->dev.backend_features = 0;
> +    vbc->dev.nvqs = vbc->num_queues;
> +    vbc->dev.vqs = vbc->vhost_vqs;
> +    vbc->dev.vq_index = 0;
> +    vbc->dev.backend_features = 0;
>  
> -    vhost_dev_set_config_notifier(&s->dev, &blk_ops);
> +    vhost_dev_set_config_notifier(&vbc->dev, &blk_ops);
>  
> -    ret = vhost_dev_init(&s->dev, &s->vhost_user, VHOST_BACKEND_TYPE_USER, 0);
> +    ret = vhost_dev_init(&vbc->dev, &s->vhost_user,
> +                         VHOST_BACKEND_TYPE_USER, 0);
>      if (ret < 0) {
>          error_report("vhost-user-blk: vhost initialization failed: %s",
>                       strerror(-ret));
> @@ -336,7 +159,7 @@ static int vhost_user_blk_connect(DeviceState *dev)
>  
>      /* restore vhost state */
>      if (virtio_device_started(vdev, vdev->status)) {
> -        ret = vhost_user_blk_start(vdev);
> +        ret = vhost_blk_common_start(vbc);
>          if (ret < 0) {
>              error_report("vhost-user-blk: vhost start failed: %s",
>                           strerror(-ret));
> @@ -351,15 +174,16 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
>  {
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>  
>      if (!s->connected) {
>          return;
>      }
>      s->connected = false;
>  
> -    vhost_user_blk_stop(vdev);
> +    vhost_blk_common_stop(vbc);
>  
> -    vhost_dev_cleanup(&s->dev);
> +    vhost_dev_cleanup(&vbc->dev);
>  }
>  
>  static void vhost_user_blk_event(void *opaque, QEMUChrEvent event,
> @@ -392,6 +216,7 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event,
>      DeviceState *dev = opaque;
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>  
>      switch (event) {
>      case CHR_EVENT_OPENED:
> @@ -430,7 +255,7 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event,
>               * option for the general vhost code to get the dev state without
>               * knowing its type (in this case vhost-user).
>               */
> -            s->dev.started = false;
> +            vbc->dev.started = false;
>          } else {
>              vhost_user_blk_disconnect(dev);
>          }
> @@ -447,42 +272,24 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
>  {
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>      Error *err = NULL;
> -    int i, ret;
> +    int ret;
>  
>      if (!s->chardev.chr) {
>          error_setg(errp, "vhost-user-blk: chardev is mandatory");
>          return;
>      }
>  
> -    if (s->num_queues == VHOST_USER_BLK_AUTO_NUM_QUEUES) {
> -        s->num_queues = 1;
> -    }
> -    if (!s->num_queues || s->num_queues > VIRTIO_QUEUE_MAX) {
> -        error_setg(errp, "vhost-user-blk: invalid number of IO queues");
> -        return;
> -    }
> -
> -    if (!s->queue_size) {
> -        error_setg(errp, "vhost-user-blk: queue size must be non-zero");
> -        return;
> -    }
> -
>      if (!vhost_user_init(&s->vhost_user, &s->chardev, errp)) {
>          return;
>      }
>  
> -    virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK,
> -                sizeof(struct virtio_blk_config));
> -
> -    s->virtqs = g_new(VirtQueue *, s->num_queues);
> -    for (i = 0; i < s->num_queues; i++) {
> -        s->virtqs[i] = virtio_add_queue(vdev, s->queue_size,
> -                                        vhost_user_blk_handle_output);
> +    vhost_blk_common_realize(vbc, vhost_user_blk_handle_output, &err);
> +    if (err != NULL) {
> +        error_propagate(errp, err);
> +        goto blk_err;
>      }
> -
> -    s->inflight = g_new0(struct vhost_inflight, 1);
> -    s->vhost_vqs = g_new0(struct vhost_virtqueue, s->num_queues);
>      s->connected = false;
>  
>      qemu_chr_fe_set_handlers(&s->chardev,  NULL, NULL,
> @@ -492,7 +299,7 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
>  reconnect:
>      if (qemu_chr_fe_wait_connected(&s->chardev, &err) < 0) {
>          error_report_err(err);
> -        goto virtio_err;
> +        goto connect_err;
>      }
>  
>      /* check whether vhost_user_blk_connect() failed or not */
> @@ -500,7 +307,7 @@ reconnect:
>          goto reconnect;
>      }
>  
> -    ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg,
> +    ret = vhost_dev_get_config(&vbc->dev, (uint8_t *)&vbc->blkcfg,
>                                 sizeof(struct virtio_blk_config));
>      if (ret < 0) {
>          error_report("vhost-user-blk: get block config failed");
> @@ -513,16 +320,9 @@ reconnect:
>                               NULL, true);
>      return;
>  
> -virtio_err:
> -    g_free(s->vhost_vqs);
> -    s->vhost_vqs = NULL;
> -    g_free(s->inflight);
> -    s->inflight = NULL;
> -    for (i = 0; i < s->num_queues; i++) {
> -        virtio_delete_queue(s->virtqs[i]);
> -    }
> -    g_free(s->virtqs);
> -    virtio_cleanup(vdev);
> +connect_err:
> +    vhost_blk_common_unrealize(vbc);
> +blk_err:
>      vhost_user_cleanup(&s->vhost_user);
>  }
>  
> @@ -530,31 +330,24 @@ static void vhost_user_blk_device_unrealize(DeviceState *dev)
>  {
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      VHostUserBlk *s = VHOST_USER_BLK(dev);
> -    int i;
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(s);
>  
>      virtio_set_status(vdev, 0);
>      qemu_chr_fe_set_handlers(&s->chardev,  NULL, NULL, NULL,
>                               NULL, NULL, NULL, false);
> -    vhost_dev_cleanup(&s->dev);
> -    vhost_dev_free_inflight(s->inflight);
> -    g_free(s->vhost_vqs);
> -    s->vhost_vqs = NULL;
> -    g_free(s->inflight);
> -    s->inflight = NULL;
> -
> -    for (i = 0; i < s->num_queues; i++) {
> -        virtio_delete_queue(s->virtqs[i]);
> -    }
> -    g_free(s->virtqs);
> -    virtio_cleanup(vdev);
> +    vhost_dev_cleanup(&vbc->dev);
> +    vhost_dev_free_inflight(vbc->inflight);
> +    vhost_blk_common_unrealize(vbc);
>      vhost_user_cleanup(&s->vhost_user);
>  }
>  
>  static void vhost_user_blk_instance_init(Object *obj)
>  {
> -    VHostUserBlk *s = VHOST_USER_BLK(obj);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(obj);
> +
> +    vbc->feature_bits = user_feature_bits;
>  
> -    device_add_bootindex_property(obj, &s->bootindex, "bootindex",
> +    device_add_bootindex_property(obj, &vbc->bootindex, "bootindex",
>                                    "/disk@0,0", DEVICE(obj));
>  }
>  
> @@ -570,10 +363,10 @@ static const VMStateDescription vmstate_vhost_user_blk = {
>  
>  static Property vhost_user_blk_properties[] = {
>      DEFINE_PROP_CHR("chardev", VHostUserBlk, chardev),
> -    DEFINE_PROP_UINT16("num-queues", VHostUserBlk, num_queues,
> -                       VHOST_USER_BLK_AUTO_NUM_QUEUES),
> -    DEFINE_PROP_UINT32("queue-size", VHostUserBlk, queue_size, 128),
> -    DEFINE_PROP_BIT("config-wce", VHostUserBlk, config_wce, 0, true),
> +    DEFINE_PROP_UINT16("num-queues", VHostBlkCommon, num_queues,
> +                       VHOST_BLK_AUTO_NUM_QUEUES),
> +    DEFINE_PROP_UINT32("queue-size", VHostBlkCommon, queue_size, 128),
> +    DEFINE_PROP_BIT("config-wce", VHostBlkCommon, config_wce, 0, true),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> @@ -587,16 +380,13 @@ static void vhost_user_blk_class_init(ObjectClass *klass, void *data)
>      set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
>      vdc->realize = vhost_user_blk_device_realize;
>      vdc->unrealize = vhost_user_blk_device_unrealize;
> -    vdc->get_config = vhost_user_blk_update_config;
> -    vdc->set_config = vhost_user_blk_set_config;
> -    vdc->get_features = vhost_user_blk_get_features;
>      vdc->set_status = vhost_user_blk_set_status;
>      vdc->reset = vhost_user_blk_reset;
>  }
>  
>  static const TypeInfo vhost_user_blk_info = {
>      .name = TYPE_VHOST_USER_BLK,
> -    .parent = TYPE_VIRTIO_DEVICE,
> +    .parent = TYPE_VHOST_BLK_COMMON,
>      .instance_size = sizeof(VHostUserBlk),
>      .instance_init = vhost_user_blk_instance_init,
>      .class_init = vhost_user_blk_class_init,
> diff --git a/hw/virtio/vhost-user-blk-pci.c b/hw/virtio/vhost-user-blk-pci.c
> index 33b404d8a2..8fb01552f5 100644
> --- a/hw/virtio/vhost-user-blk-pci.c
> +++ b/hw/virtio/vhost-user-blk-pci.c
> @@ -54,13 +54,14 @@ static void vhost_user_blk_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>  {
>      VHostUserBlkPCI *dev = VHOST_USER_BLK_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
> +    VHostBlkCommon *vbc = VHOST_BLK_COMMON(&dev->vdev);
>  
> -    if (dev->vdev.num_queues == VHOST_USER_BLK_AUTO_NUM_QUEUES) {
> -        dev->vdev.num_queues = virtio_pci_optimal_num_queues(0);
> +    if (vbc->num_queues == VHOST_BLK_AUTO_NUM_QUEUES) {
> +        vbc->num_queues = virtio_pci_optimal_num_queues(0);
>      }
>  
>      if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> -        vpci_dev->nvectors = dev->vdev.num_queues + 1;
> +        vpci_dev->nvectors = vbc->num_queues + 1;
>      }
>  
>      qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
> diff --git a/include/hw/virtio/vhost-blk-common.h b/include/hw/virtio/vhost-blk-common.h
> new file mode 100644
> index 0000000000..1a12a58b60
> --- /dev/null
> +++ b/include/hw/virtio/vhost-blk-common.h
> @@ -0,0 +1,50 @@
> +/*
> + * Parent class for vhost based block devices
> + *
> + * Copyright (C) 2021 Bytedance Inc. and/or its affiliates. All rights reserved.
> + *
> + * Author:
> + *   Xie Yongji <xieyongji@bytedance.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef VHOST_BLK_COMMON_H
> +#define VHOST_BLK_COMMON_H
> +
> +#include "standard-headers/linux/virtio_blk.h"
> +#include "hw/virtio/vhost.h"
> +#include "qom/object.h"
> +
> +#define TYPE_VHOST_BLK_COMMON "vhost-blk-common"
> +OBJECT_DECLARE_SIMPLE_TYPE(VHostBlkCommon, VHOST_BLK_COMMON)
> +
> +#define VHOST_BLK_AUTO_NUM_QUEUES UINT16_MAX
> +
> +struct VHostBlkCommon {
> +    VirtIODevice parent_obj;
> +    int32_t bootindex;
> +    struct virtio_blk_config blkcfg;
> +    uint16_t num_queues;
> +    uint32_t queue_size;
> +    const int *feature_bits;
> +    uint32_t config_wce;
> +    struct vhost_dev dev;
> +    struct vhost_inflight *inflight;
> +    struct vhost_virtqueue *vhost_vqs;
> +    VirtQueue **virtqs;

As discussed above please rename this, and add a comment explaining that
it prevents stopping an already stopped device.

> +    bool started;
> +};
> +
> +extern const VhostDevConfigOps blk_ops;
> +
> +int vhost_blk_common_start(VHostBlkCommon *vbc);
> +void vhost_blk_common_stop(VHostBlkCommon *vbc);
> +void vhost_blk_common_realize(VHostBlkCommon *vbc,
> +                              VirtIOHandleOutput handle_output,
> +                              Error **errp);
> +void vhost_blk_common_unrealize(VHostBlkCommon *vbc);
> +
> +#endif
> diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h
> index 7c91f15040..100275602f 100644
> --- a/include/hw/virtio/vhost-user-blk.h
> +++ b/include/hw/virtio/vhost-user-blk.h
> @@ -15,32 +15,18 @@
>  #ifndef VHOST_USER_BLK_H
>  #define VHOST_USER_BLK_H
>  
> -#include "standard-headers/linux/virtio_blk.h"
> -#include "hw/block/block.h"
>  #include "chardev/char-fe.h"
> -#include "hw/virtio/vhost.h"
>  #include "hw/virtio/vhost-user.h"
> +#include "hw/virtio/vhost-blk-common.h"
>  #include "qom/object.h"
>  
>  #define TYPE_VHOST_USER_BLK "vhost-user-blk"
>  OBJECT_DECLARE_SIMPLE_TYPE(VHostUserBlk, VHOST_USER_BLK)
>  
> -#define VHOST_USER_BLK_AUTO_NUM_QUEUES UINT16_MAX
> -
>  struct VHostUserBlk {
> -    VirtIODevice parent_obj;
> +    VHostBlkCommon parent_obj;
>      CharBackend chardev;
> -    int32_t bootindex;
> -    struct virtio_blk_config blkcfg;
> -    uint16_t num_queues;
> -    uint32_t queue_size;
> -    uint32_t config_wce;
> -    struct vhost_dev dev;
> -    struct vhost_inflight *inflight;
>      VhostUserState vhost_user;
> -    struct vhost_virtqueue *vhost_vqs;
> -    VirtQueue **virtqs;
> -

Please fix this comment to explain that the started_vu now lives in
vhost-blk-common.

>      /*
>       * There are at least two steps of initialization of the
>       * vhost-user device. The first is a "connect" step and
> @@ -49,8 +35,6 @@ struct VHostUserBlk {
>       */
>      /* vhost_user_blk_connect/vhost_user_blk_disconnect */
>      bool connected;
> -    /* vhost_user_blk_start/vhost_user_blk_stop */
> -    bool started_vu;
>  };
>  
>  #endif
> -- 
> 2.25.1
>