Re: [PATCH v4 6/6] vdpa: Always start CVQ in SVQ mode

[Jason Wang]

On Sat, Aug 6, 2022 at 12:39 AM 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>
> ---
> 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       | 124 +++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 122 insertions(+), 5 deletions(-)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 3eb67b27b7..69f34f4cc5 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -678,7 +678,8 @@ 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 bf78b1332f..c820a5fd9f 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -37,6 +37,9 @@ typedef struct VhostVDPAState {
>      /* Control commands shadow buffers */
>      void *cvq_cmd_out_buffer, *cvq_cmd_in_buffer;
>
> +    /* Number of address spaces supported by the device */
> +    unsigned address_space_num;
> +
>      /* The device always have SVQ enabled */
>      bool always_svq;
>      bool started;
> @@ -100,6 +103,9 @@ 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_PASSTHROUGH 0

We need a better name for the macro since it's not easy to see it's an asid.

> +#define VHOST_VDPA_NET_CVQ_ASID 1
> +
>  VHostNetState *vhost_vdpa_get_vhost_net(NetClientState *nc)
>  {
>      VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> @@ -224,6 +230,37 @@ static NetClientInfo net_vhost_vdpa_info = {
>          .check_peer_type = vhost_vdpa_check_peer_type,
>  };
>
> +static void vhost_vdpa_get_vring_group(int device_fd,
> +                                       struct vhost_vring_state *state)
> +{
> +    int r = ioctl(device_fd, VHOST_VDPA_GET_VRING_GROUP, state);

Let's hide vhost_vring_state from the caller and simply accept a vq
index parameter (as the below function did) then we can return the
group id.

The hides low level ABI and simplify the caller's code.

> +    if (unlikely(r < 0)) {
> +        /*
> +         * Assume all groups are 0, the consequences are the same and we will
> +         * not abort device creation
> +         */
> +        state->num = 0;
> +    }
> +}
> +
> +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 ret;
> +
> +    ret = ioctl(v->device_fd, VHOST_VDPA_SET_GROUP_ASID, &asid);
> +    if (unlikely(ret < 0)) {
> +        warn_report("Can't set vq group %u asid %u, errno=%d (%s)",
> +            asid.index, asid.num, errno, g_strerror(errno));
> +    }
> +    return ret;
> +}
> +
>  static void vhost_vdpa_cvq_unmap_buf(struct vhost_vdpa *v, void *addr)
>  {
>      VhostIOVATree *tree = v->iova_tree;
> @@ -298,11 +335,55 @@ dma_map_err:
>  static int vhost_vdpa_net_cvq_prepare(NetClientState *nc)
>  {
>      VhostVDPAState *s;
> +    struct vhost_vdpa *v;
> +    struct vhost_vring_state cvq_group = {};
>      int r;
>
>      assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>
>      s = DO_UPCAST(VhostVDPAState, nc, nc);
> +    v = &s->vhost_vdpa;
> +    cvq_group.index = v->dev->vq_index_end - 1;
> +
> +    /* Default values */

Code can explain itself so this comment is probably useless.

> +    v->shadow_vqs_enabled = false;
> +    s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_PASSTHROUGH;
> +
> +    if (s->always_svq) {
> +        v->shadow_vqs_enabled = true;

The name of the variable is suboptimal.

I think we need to differ:

1) shadow all virtqueues

from

2) shadow cvq only

Thanks

> +        goto out;
> +    }
> +
> +    if (s->address_space_num < 2) {
> +        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.
> +     */
> +    vhost_vdpa_get_vring_group(v->device_fd, &cvq_group);
> +    for (int i = 0; i < (v->dev->vq_index_end - 1); ++i) {
> +        struct vhost_vring_state vq_group = {
> +            .index = i,
> +        };
> +
> +        vhost_vdpa_get_vring_group(v->device_fd, &vq_group);
> +        if (unlikely(vq_group.num == cvq_group.num)) {
> +            warn_report("CVQ %u group is the same as VQ %u one (%u)",
> +                         cvq_group.index, vq_group.index, cvq_group.num);
> +            return 0;
> +        }
> +    }
> +
> +    r = vhost_vdpa_set_address_space_id(v, cvq_group.num,
> +                                        VHOST_VDPA_NET_CVQ_ASID);
> +    if (r == 0) {
> +        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;
>      }
> @@ -523,12 +604,38 @@ static const VhostShadowVirtqueueOps 
> vhost_vdpa_net_svq_ops = {
>      .avail_handler = vhost_vdpa_net_handle_ctrl_avail,
>  };
>
> +static uint32_t vhost_vdpa_get_as_num(int vdpa_device_fd)
> +{
> +    uint64_t features;
> +    unsigned num_as;
> +    int r;
> +
> +    r = ioctl(vdpa_device_fd, VHOST_GET_BACKEND_FEATURES, &features);
> +    if (unlikely(r < 0)) {
> +        warn_report("Cannot get backend features");
> +        return 1;
> +    }
> +
> +    if (!(features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID))) {
> +        return 1;
> +    }
> +
> +    r = ioctl(vdpa_device_fd, VHOST_VDPA_GET_AS_NUM, &num_as);
> +    if (unlikely(r < 0)) {
> +        warn_report("Cannot retrieve number of supported ASs");
> +        return 1;
> +    }
> +
> +    return num_as;
> +}
> +
>  static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
>                                             const char *device,
>                                             const char *name,
>                                             int vdpa_device_fd,
>                                             int queue_pair_index,
>                                             int nvqs,
> +                                           unsigned nas,
>                                             bool is_datapath,
>                                             bool svq,
>                                             VhostIOVATree *iova_tree)
> @@ -547,6 +654,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState 
> *peer,
>      snprintf(nc->info_str, sizeof(nc->info_str), TYPE_VHOST_VDPA);
>      s = DO_UPCAST(VhostVDPAState, nc, nc);
>
> +    s->address_space_num = nas;
>      s->vhost_vdpa.device_fd = vdpa_device_fd;
>      s->vhost_vdpa.index = queue_pair_index;
>      s->always_svq = svq;
> @@ -632,6 +740,8 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char 
> *name,
>      g_autoptr(VhostIOVATree) iova_tree = NULL;
>      NetClientState *nc;
>      int queue_pairs, r, i = 0, has_cvq = 0;
> +    unsigned num_as = 1;
> +    bool svq_cvq;
>
>      assert(netdev->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>      opts = &netdev->u.vhost_vdpa;
> @@ -656,7 +766,13 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char 
> *name,
>          goto err;
>      }
>
> -    if (opts->x_svq) {
> +    svq_cvq = opts->x_svq;
> +    if (has_cvq && !opts->x_svq) {
> +        num_as = vhost_vdpa_get_as_num(vdpa_device_fd);
> +        svq_cvq = num_as > 1;
> +    }
> +
> +    if (opts->x_svq || svq_cvq) {
>          struct vhost_vdpa_iova_range iova_range;
>
>          uint64_t invalid_dev_features =
> @@ -679,15 +795,15 @@ int net_init_vhost_vdpa(const Netdev *netdev, const 
> char *name,
>
>      for (i = 0; i < queue_pairs; i++) {
>          ncs[i] = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> -                                     vdpa_device_fd, i, 2, true, opts->x_svq,
> -                                     iova_tree);
> +                                     vdpa_device_fd, i, 2, num_as, true,
> +                                     opts->x_svq, iova_tree);
>          if (!ncs[i])
>              goto err;
>      }
>
>      if (has_cvq) {
>          nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> -                                 vdpa_device_fd, i, 1, false,
> +                                 vdpa_device_fd, i, 1, num_as, false,
>                                   opts->x_svq, iova_tree);
>          if (!nc)
>              goto err;
> --
> 2.31.1
>