Re: [PATCH v9 12/12] vdpa: always start CVQ in SVQ mode if possible

[Jason Wang]

On Thu, Dec 15, 2022 at 7:32 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> Isolate control virtqueue in its own group, allowing to intercept control
> commands but letting dataplane run totally passthrough to the guest.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

> ---
> v9:
> * Reuse iova_range fetched from the device at initialization, instead of
>   fetch it again at vhost_vdpa_net_cvq_start.
> * Add comment about how migration is blocked in case ASID does not met
>   our expectations.
> * Delete warning about CVQ group not being independent.
>
> v8:
> * Do not allocate iova_tree on net_init_vhost_vdpa if only CVQ is
>   shadowed. Move the iova_tree handling in this case to
>   vhost_vdpa_net_cvq_start and vhost_vdpa_net_cvq_stop.
>
> v7:
> * Never ask for number of address spaces, just react if isolation is not
>   possible.
> * Return ASID ioctl errors instead of masking them as if the device has
>   no asid.
> * Simplify net_init_vhost_vdpa logic
> * Add "if possible" suffix
>
> v6:
> * Disable control SVQ if the device does not support it because of
> features.
>
> v5:
> * Fixing the not adding cvq buffers when x-svq=on is specified.
> * Move vring state in vhost_vdpa_get_vring_group instead of using a
>   parameter.
> * Rename VHOST_VDPA_NET_CVQ_PASSTHROUGH to VHOST_VDPA_NET_DATA_ASID
>
> v4:
> * Squash vhost_vdpa_cvq_group_is_independent.
> * Rebased on last CVQ start series, that allocated CVQ cmd bufs at load
> * Do not check for cvq index on vhost_vdpa_net_prepare, we only have one
>   that callback registered in that NetClientInfo.
>
> v3:
> * Make asid related queries print a warning instead of returning an
>   error and stop the start of qemu.
> ---
>  hw/virtio/vhost-vdpa.c |   3 +-
>  net/vhost-vdpa.c       | 110 ++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 111 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 48d8c60e76..8cd00f5a96 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -638,7 +638,8 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev 
> *dev)
>  {
>      uint64_t features;
>      uint64_t f = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
> -        0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH;
> +        0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH |
> +        0x1ULL << VHOST_BACKEND_F_IOTLB_ASID;
>      int r;
>
>      if (vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES, &features)) {
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 710c5efe96..d36664f33a 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -102,6 +102,8 @@ static const uint64_t vdpa_svq_device_features =
>      BIT_ULL(VIRTIO_NET_F_RSC_EXT) |
>      BIT_ULL(VIRTIO_NET_F_STANDBY);
>
> +#define VHOST_VDPA_NET_CVQ_ASID 1
> +
>  VHostNetState *vhost_vdpa_get_vhost_net(NetClientState *nc)
>  {
>      VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> @@ -243,6 +245,40 @@ static NetClientInfo net_vhost_vdpa_info = {
>          .check_peer_type = vhost_vdpa_check_peer_type,
>  };
>
> +static int64_t vhost_vdpa_get_vring_group(int device_fd, unsigned vq_index)
> +{
> +    struct vhost_vring_state state = {
> +        .index = vq_index,
> +    };
> +    int r = ioctl(device_fd, VHOST_VDPA_GET_VRING_GROUP, &state);
> +
> +    if (unlikely(r < 0)) {
> +        error_report("Cannot get VQ %u group: %s", vq_index,
> +                     g_strerror(errno));
> +        return r;
> +    }
> +
> +    return state.num;
> +}
> +
> +static int vhost_vdpa_set_address_space_id(struct vhost_vdpa *v,
> +                                           unsigned vq_group,
> +                                           unsigned asid_num)
> +{
> +    struct vhost_vring_state asid = {
> +        .index = vq_group,
> +        .num = asid_num,
> +    };
> +    int r;
> +
> +    r = ioctl(v->device_fd, VHOST_VDPA_SET_GROUP_ASID, &asid);
> +    if (unlikely(r < 0)) {
> +        error_report("Can't set vq group %u asid %u, errno=%d (%s)",
> +                     asid.index, asid.num, errno, g_strerror(errno));
> +    }
> +    return r;
> +}
> +
>  static void vhost_vdpa_cvq_unmap_buf(struct vhost_vdpa *v, void *addr)
>  {
>      VhostIOVATree *tree = v->iova_tree;
> @@ -317,11 +353,75 @@ dma_map_err:
>  static int vhost_vdpa_net_cvq_start(NetClientState *nc)
>  {
>      VhostVDPAState *s;
> -    int r;
> +    struct vhost_vdpa *v;
> +    uint64_t backend_features;
> +    int64_t cvq_group;
> +    int cvq_index, r;
>
>      assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>
>      s = DO_UPCAST(VhostVDPAState, nc, nc);
> +    v = &s->vhost_vdpa;
> +
> +    v->shadow_data = s->always_svq;
> +    v->shadow_vqs_enabled = s->always_svq;
> +    s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
> +
> +    if (s->always_svq) {
> +        /* SVQ is already configured for all virtqueues */
> +        goto out;
> +    }
> +
> +    /*
> +     * If we early return in these cases SVQ will not be enabled. The 
> migration
> +     * will be blocked as long as vhost-vdpa backends will not offer _F_LOG.
> +     *
> +     * Calling VHOST_GET_BACKEND_FEATURES as they are not available in v->dev
> +     * yet.
> +     */
> +    r = ioctl(v->device_fd, VHOST_GET_BACKEND_FEATURES, &backend_features);
> +    if (unlikely(r < 0)) {
> +        error_report("Cannot get vdpa backend_features: %s(%d)",
> +            g_strerror(errno), errno);
> +        return -1;
> +    }
> +    if (!(backend_features & VHOST_BACKEND_F_IOTLB_ASID) ||
> +        !vhost_vdpa_net_valid_svq_features(v->dev->features, NULL)) {
> +        return 0;
> +    }
> +
> +    /*
> +     * Check if all the virtqueues of the virtio device are in a different vq
> +     * than the last vq. VQ group of last group passed in cvq_group.
> +     */
> +    cvq_index = v->dev->vq_index_end - 1;
> +    cvq_group = vhost_vdpa_get_vring_group(v->device_fd, cvq_index);
> +    if (unlikely(cvq_group < 0)) {
> +        return cvq_group;
> +    }
> +    for (int i = 0; i < cvq_index; ++i) {
> +        int64_t group = vhost_vdpa_get_vring_group(v->device_fd, i);
> +
> +        if (unlikely(group < 0)) {
> +            return group;
> +        }
> +
> +        if (group == cvq_group) {
> +            return 0;
> +        }
> +    }
> +
> +    r = vhost_vdpa_set_address_space_id(v, cvq_group, 
> VHOST_VDPA_NET_CVQ_ASID);
> +    if (unlikely(r < 0)) {
> +        return r;
> +    }
> +
> +    v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
> +                                       v->iova_range.last);
> +    v->shadow_vqs_enabled = true;
> +    s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_ASID;
> +
> +out:
>      if (!s->vhost_vdpa.shadow_vqs_enabled) {
>          return 0;
>      }
> @@ -350,6 +450,14 @@ static void vhost_vdpa_net_cvq_stop(NetClientState *nc)
>      if (s->vhost_vdpa.shadow_vqs_enabled) {
>          vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
>          vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
> +        if (!s->always_svq) {
> +            /*
> +             * If only the CVQ is shadowed we can delete this safely.
> +             * If all the VQs are shadows this will be needed by the time the
> +             * device is started again to register SVQ vrings and similar.
> +             */
> +            g_clear_pointer(&s->vhost_vdpa.iova_tree, 
> vhost_iova_tree_delete);
> +        }
>      }
>  }
>
> --
> 2.31.1
>