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

[Jason Wang]

On Tue, Aug 9, 2022 at 3:54 PM Eugenio Perez Martin <eperezma@redhat.com> wrote:
>
> On Tue, Aug 9, 2022 at 9:36 AM Jason Wang <jasowang@redhat.com> wrote:
> >
> > 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.
> >
>
> VHOST_VDPA_NET_DATA_ASID?

Looks fine.

>
> > > +#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.
> >
>
> We need to return an error.
>
> The example is a little bit pathological, but if we get that CVQ is on
> vq group != 0, and all data vqs returns an error reading the vq group,
> I think we shouldn't assume they belong to the asid 0. Some of them
> could be on the same vq group as cvq, making all of this fail.
>
> Can we assume the vq group is an uint32_t? Would it work to return an
> int64_t with the possibility of errors?

Yes, or I think a simple int should be fine, I can't image we will
make use of the full 32 bit in near future.

>
> > > +    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.
> >
>
> I'll delete.
>
> > > +    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
> >
>
> Note that shadow_vqs_enabled is per vhost_vdpa, so
> v->shadow_vqs_enabled means that vqs of *v* are shadowed.
>
> Data vhost_vdpa can have a different value than CVQ vhost_vdpa.
>
> Having said that, I'm ok with changing the name of the variable, but I
> cannot come with a better one.

Ok, let's leave it as is.

Thanks

>
> Thanks!
>
> > 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
> > >
> >
>