Re: [RFC] vhost-vdpa-net: add vhost-vdpa-net host device support

[Jason Wang]

On Wed, Dec 8, 2021 at 1:20 PM Longpeng(Mike) <longpeng2@huawei.com> wrote:
>
> From: Longpeng <longpeng2@huawei.com>
>
> Hi guys,
>
> This patch introduces vhost-vdpa-net device, which is inspired
> by vhost-user-blk and the proposal of vhost-vdpa-blk device [1].
>
> I've tested this patch on Huawei's offload card:
> ./x86_64-softmmu/qemu-system-x86_64 \
>     -device vhost-vdpa-net-pci,vdpa-dev=/dev/vhost-vdpa-0
>
> For virtio hardware offloading, the most important requirement for us
> is to support live migration between offloading cards from different
> vendors, the combination of netdev and virtio-net seems too heavy, we
> prefer a lightweight way.

Could you elaborate more on this? It's mainly the control path when
using with netdev, and it provides a lot of other benefits:

- decouple the transport specific stuff out of the vhost abstraction,
mmio device is supported with 0 line of code
- migration compatibility, reuse the migration stream that is already
supported by Qemu virtio-net, this will allow migration among
different vhost backends.
- software mediation facility, not all the virtqueues are assigned to
guests directly. One example is the virtio-net cvq, qemu may want to
intercept and record the device state for migration. Reusing the
current virtio-net codes simplifies a lot of codes.
- transparent failover (in the future), the nic model can choose to
switch between vhost backends etc.

>
> Maybe we could support both in the future ?

For the net, we need to figure out the advantages of this approach
first. Note that we didn't have vhost-user-net-pci or vhost-pci in the
past.

For the block, I will leave Stefan and Stefano to comment.

> Such as:
>
> * Lightweight
>  Net: vhost-vdpa-net
>  Storage: vhost-vdpa-blk
>
> * Heavy but more powerful
>  Net: netdev + virtio-net + vhost-vdpa
>  Storage: bdrv + virtio-blk + vhost-vdpa
>
> [1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg797569.html
>
> Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
> ---
>  hw/net/meson.build                 |   1 +
>  hw/net/vhost-vdpa-net.c            | 338 
> +++++++++++++++++++++++++++++++++++++
>  hw/virtio/Kconfig                  |   5 +
>  hw/virtio/meson.build              |   1 +
>  hw/virtio/vhost-vdpa-net-pci.c     | 118 +++++++++++++

I'd expect there's no device type specific code in this approach and
any kind of vDPA devices could be used with a general pci device.

Any reason for having net specific types here?

>  include/hw/virtio/vhost-vdpa-net.h |  31 ++++
>  include/net/vhost-vdpa.h           |   2 +
>  net/vhost-vdpa.c                   |   2 +-
>  8 files changed, 497 insertions(+), 1 deletion(-)
>  create mode 100644 hw/net/vhost-vdpa-net.c
>  create mode 100644 hw/virtio/vhost-vdpa-net-pci.c
>  create mode 100644 include/hw/virtio/vhost-vdpa-net.h
>
> diff --git a/hw/net/meson.build b/hw/net/meson.build
> index bdf71f1..139ebc4 100644
> --- a/hw/net/meson.build
> +++ b/hw/net/meson.build
> @@ -44,6 +44,7 @@ specific_ss.add(when: 'CONFIG_XILINX_ETHLITE', if_true: 
> files('xilinx_ethlite.c'
>
>  softmmu_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('net_rx_pkt.c'))
>  specific_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio-net.c'))
> +specific_ss.add(when: 'CONFIG_VHOST_VDPA_NET', if_true: 
> files('vhost-vdpa-net.c'))
>
>  softmmu_ss.add(when: ['CONFIG_VIRTIO_NET', 'CONFIG_VHOST_NET'], if_true: 
> files('vhost_net.c'), if_false: files('vhost_net-stub.c'))
>  softmmu_ss.add(when: 'CONFIG_ALL', if_true: files('vhost_net-stub.c'))
> diff --git a/hw/net/vhost-vdpa-net.c b/hw/net/vhost-vdpa-net.c
> new file mode 100644
> index 0000000..48b99f9
> --- /dev/null
> +++ b/hw/net/vhost-vdpa-net.c
> @@ -0,0 +1,338 @@
> +#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/vhost-vdpa-net.h"
> +#include "hw/virtio/virtio.h"
> +#include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/virtio-access.h"
> +#include "sysemu/sysemu.h"
> +#include "sysemu/runstate.h"
> +#include "net/vhost-vdpa.h"
> +
> +static void vhost_vdpa_net_get_config(VirtIODevice *vdev, uint8_t *config)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +
> +    memcpy(config, &s->netcfg, sizeof(struct virtio_net_config));
> +}
> +
> +static void vhost_vdpa_net_set_config(VirtIODevice *vdev, const uint8_t 
> *config)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +    struct virtio_net_config *netcfg = (struct virtio_net_config *)config;
> +    int ret;
> +
> +    ret = vhost_dev_set_config(&s->dev, (uint8_t *)netcfg, 0, 
> sizeof(*netcfg),
> +                               VHOST_SET_CONFIG_TYPE_MASTER);
> +    if (ret) {
> +        error_report("set device config space failed");
> +        return;
> +    }
> +}
> +
> +static uint64_t vhost_vdpa_net_get_features(VirtIODevice *vdev,
> +                                            uint64_t features,
> +                                            Error **errp)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +
> +    virtio_add_feature(&features, VIRTIO_NET_F_CSUM);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GUEST_CSUM);
> +    virtio_add_feature(&features, VIRTIO_NET_F_MAC);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GSO);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GUEST_TSO4);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GUEST_TSO6);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GUEST_ECN);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GUEST_UFO);
> +    virtio_add_feature(&features, VIRTIO_NET_F_GUEST_ANNOUNCE);
> +    virtio_add_feature(&features, VIRTIO_NET_F_HOST_TSO4);
> +    virtio_add_feature(&features, VIRTIO_NET_F_HOST_TSO6);
> +    virtio_add_feature(&features, VIRTIO_NET_F_HOST_ECN);
> +    virtio_add_feature(&features, VIRTIO_NET_F_HOST_UFO);
> +    virtio_add_feature(&features, VIRTIO_NET_F_MRG_RXBUF);
> +    virtio_add_feature(&features, VIRTIO_NET_F_STATUS);
> +    virtio_add_feature(&features, VIRTIO_NET_F_CTRL_VQ);
> +    virtio_add_feature(&features, VIRTIO_NET_F_CTRL_RX);
> +    virtio_add_feature(&features, VIRTIO_NET_F_CTRL_VLAN);
> +    virtio_add_feature(&features, VIRTIO_NET_F_CTRL_RX_EXTRA);
> +    virtio_add_feature(&features, VIRTIO_NET_F_CTRL_MAC_ADDR);
> +    virtio_add_feature(&features, VIRTIO_NET_F_MQ);

Any reason for those hand crafted features?

> +
> +    return vhost_get_features(&s->dev, vdpa_feature_bits, features);
> +}
> +
> +static int vhost_vdpa_net_start(VirtIODevice *vdev, Error **errp)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(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_setg(errp, "binding does not support guest notifiers");
> +        return -ENOSYS;
> +    }
> +
> +    ret = vhost_dev_enable_notifiers(&s->dev, vdev);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "Error enabling host notifiers");
> +        return ret;
> +    }
> +
> +    ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, true);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "Error binding guest notifier");
> +        goto err_host_notifiers;
> +    }
> +
> +    s->dev.acked_features = vdev->guest_features;
> +
> +    ret = vhost_dev_start(&s->dev, vdev);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "Error starting vhost");
> +        goto err_guest_notifiers;
> +    }
> +    s->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 < 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_vdpa_net_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +    Error *local_err = NULL;
> +    int i, ret;
> +
> +    if (!vdev->start_on_kick) {
> +        return;
> +    }
> +
> +    if (s->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_vdpa_net_start(vdev, &local_err);
> +    if (ret < 0) {
> +        error_reportf_err(local_err, "vhost-vdpa-net: start failed: ");
> +        return;
> +    }
> +
> +    /* Kick right away to begin processing requests already in vring */
> +    for (i = 0; i < s->dev.nvqs; i++) {
> +        VirtQueue *kick_vq = virtio_get_queue(vdev, i);
> +
> +        if (!virtio_queue_get_desc_addr(vdev, i)) {
> +            continue;
> +        }
> +        event_notifier_set(virtio_queue_get_host_notifier(kick_vq));
> +    }
> +}
> +
> +static void vhost_vdpa_net_stop(VirtIODevice *vdev)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> +    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +    int ret;
> +
> +    if (!s->started) {
> +        return;
> +    }
> +    s->started = 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_vdpa_net_set_status(VirtIODevice *vdev, uint8_t status)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +    bool should_start = virtio_device_started(vdev, status);
> +    Error *local_err = NULL;
> +    int ret;
> +
> +    if (!vdev->vm_running) {
> +        should_start = false;
> +    }
> +
> +    if (s->started == should_start) {
> +        return;
> +    }
> +
> +    if (should_start) {
> +        ret = vhost_vdpa_net_start(vdev, &local_err);
> +        if (ret < 0) {
> +            error_reportf_err(local_err, "vhost-vdpa-net: start failed: ");
> +        }
> +    } else {
> +        vhost_vdpa_net_stop(vdev);
> +    }
> +}
> +
> +static void vhost_vdpa_net_unrealize(VHostVdpaNet *s)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(s);
> +    int i;
> +
> +    for (i = 0; i < s->queue_pairs * 2; i++) {
> +        virtio_delete_queue(s->virtqs[i]);
> +    }
> +    /* ctrl vq */
> +    virtio_delete_queue(s->virtqs[i]);
> +
> +    g_free(s->virtqs);
> +    virtio_cleanup(vdev);
> +}
> +
> +static void vhost_vdpa_net_device_realize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +    int i, ret;
> +
> +    s->vdpa.device_fd = qemu_open_old(s->vdpa_dev, O_RDWR);
> +    if (s->vdpa.device_fd == -1) {
> +        error_setg(errp, "vhost-vdpa-net: open %s failed: %s",
> +                   s->vdpa_dev, strerror(errno));
> +        return;
> +    }
> +
> +    virtio_init(vdev, "virtio-net", VIRTIO_ID_NET,
> +                sizeof(struct virtio_net_config));
> +
> +    s->dev.nvqs = s->queue_pairs * 2 + 1;
> +    s->dev.vqs = g_new0(struct vhost_virtqueue, s->dev.nvqs);
> +    s->dev.vq_index = 0;
> +    s->dev.vq_index_end = s->dev.nvqs;
> +    s->dev.backend_features = 0;
> +    s->started = false;
> +
> +    s->virtqs = g_new0(VirtQueue *, s->dev.nvqs);
> +    for (i = 0; i < s->dev.nvqs; i++) {
> +        s->virtqs[i] = virtio_add_queue(vdev, s->queue_size,
> +                                        vhost_vdpa_net_handle_output);

We should check whether MQ is negotiated since the index varies
depending on that.

> +    }
> +
> +    ret = vhost_dev_init(&s->dev, &s->vdpa, VHOST_BACKEND_TYPE_VDPA, 0, 
> NULL);
> +    if (ret < 0) {
> +        error_setg(errp, "vhost-vdpa-net: vhost initialization failed: %s",
> +                   strerror(-ret));
> +        goto init_err;
> +    }
> +
> +    ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->netcfg,
> +                               sizeof(struct virtio_net_config), NULL);
> +    if (ret < 0) {
> +        error_setg(errp, "vhost-vdpa-net: get network config failed");
> +        goto config_err;
> +    }
> +
> +    return;
> +config_err:
> +    vhost_dev_cleanup(&s->dev);
> +init_err:
> +    vhost_vdpa_net_unrealize(s);
> +    close(s->vdpa.device_fd);
> +}
> +
> +static void vhost_vdpa_net_device_unrealize(DeviceState *dev)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VHostVdpaNet *s = VHOST_VDPA_NET(vdev);
> +
> +    virtio_set_status(vdev, 0);
> +    vhost_dev_cleanup(&s->dev);
> +    vhost_vdpa_net_unrealize(s);
> +    close(s->vdpa.device_fd);
> +}
> +
> +static const VMStateDescription vmstate_vhost_vdpa_net = {
> +    .name = "vhost-vdpa-net",
> +    .minimum_version_id = 1,
> +    .version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_VIRTIO_DEVICE,
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
> +static void vhost_vdpa_net_instance_init(Object *obj)
> +{
> +    VHostVdpaNet *s = VHOST_VDPA_NET(obj);
> +
> +    device_add_bootindex_property(obj, &s->bootindex, "bootindex",
> +                                  "/ethernet-phy@0,0", DEVICE(obj));
> +}
> +
> +static Property vhost_vdpa_net_properties[] = {
> +    DEFINE_PROP_STRING("vdpa-dev", VHostVdpaNet, vdpa_dev),
> +    DEFINE_PROP_UINT16("queue-pairs", VHostVdpaNet, queue_pairs,
> +                       VHOST_VDPA_NET_AUTO_QUEUE_PAIRS),

Any reason that we need the queue pairs parameter? Note that it is
expected to be provisioned by the netlink for the management device.

Thanks