Re: [RFC v2 02/13] vdpa net: move iova tree creation from init to start

[Eugenio Perez Martin]

On Fri, Jan 13, 2023 at 4:53 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Fri, Jan 13, 2023 at 1:24 AM Eugenio Pérez <eperezma@redhat.com> wrote:
> >
> > Only create iova_tree if and when it is needed.
> >
> > The cleanup keeps being responsability of last VQ but this change allows
> > to merge both cleanup functions.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > ---
> >  net/vhost-vdpa.c | 101 +++++++++++++++++++++++++++++++++--------------
> >  1 file changed, 71 insertions(+), 30 deletions(-)
> >
> > diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> > index de5ed8ff22..75cca497c8 100644
> > --- a/net/vhost-vdpa.c
> > +++ b/net/vhost-vdpa.c
> > @@ -178,13 +178,9 @@ err_init:
> >  static void vhost_vdpa_cleanup(NetClientState *nc)
> >  {
> >      VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> > -    struct vhost_dev *dev = &s->vhost_net->dev;
> >
> >      qemu_vfree(s->cvq_cmd_out_buffer);
> >      qemu_vfree(s->status);
> > -    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
> > -        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
> > -    }
> >      if (s->vhost_net) {
> >          vhost_net_cleanup(s->vhost_net);
> >          g_free(s->vhost_net);
> > @@ -234,10 +230,64 @@ static ssize_t vhost_vdpa_receive(NetClientState *nc, 
> > const uint8_t *buf,
> >      return size;
> >  }
> >
> > +/** From any vdpa net client, get the netclient of first queue pair */
> > +static VhostVDPAState *vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
> > +{
> > +    NICState *nic = qemu_get_nic(s->nc.peer);
> > +    NetClientState *nc0 = qemu_get_peer(nic->ncs, 0);
> > +
> > +    return DO_UPCAST(VhostVDPAState, nc, nc0);
> > +}
> > +
> > +static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
> > +{
> > +    struct vhost_vdpa *v = &s->vhost_vdpa;
> > +
> > +    if (v->shadow_vqs_enabled) {
> > +        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
> > +                                           v->iova_range.last);
> > +    }
> > +}
> > +
> > +static int vhost_vdpa_net_data_start(NetClientState *nc)
> > +{
> > +    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> > +    struct vhost_vdpa *v = &s->vhost_vdpa;
> > +
> > +    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
> > +
> > +    if (v->index == 0) {
> > +        vhost_vdpa_net_data_start_first(s);
> > +        return 0;
> > +    }
> > +
> > +    if (v->shadow_vqs_enabled) {
> > +        VhostVDPAState *s0 = vhost_vdpa_net_first_nc_vdpa(s);
> > +        v->iova_tree = s0->vhost_vdpa.iova_tree;
> > +    }
>
> It looks to me the logic here is somehow the same as
> vhost_vdpa_net_cvq_start(), can we unify the them?
>

It depends on what you mean by unify :). But we can explore it for sure.

We can call vhost_vdpa_net_data_start, but the steps to do if
s0->vhost_vdpa.iova_tree == NULL are different. Data queues must do
nothing, but CVQ must create a new iova tree.

So one possibility is to convert this part of vhost_vdpa_net_cvq_start:
    s0 = vhost_vdpa_net_first_nc_vdpa(s);
    if (s0->vhost_vdpa.iova_tree) {
        /* SVQ is already configured for all virtqueues */
        v->iova_tree = s0->vhost_vdpa.iova_tree;
    } else {
        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
                                           v->iova_range.last);
    }

into:
    vhost_vdpa_net_data_start(nc);
    if (!v->iova_tree) {
        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
                                           v->iova_range.last);
    }

I'm ok with the change but it's less clear in my opinion: it's not
obvious that net_data_start is in charge of setting v->iova_tree to
me.

Another possibility is to abstract something like
first_nc_iova_tree(), but we need to check more fields of s0 later
(shadow_data) so I'm not sure about the benefit.

Is that what you have in mind?

Thanks!

> > +
> > +    return 0;
> > +}
> > +
> > +static void vhost_vdpa_net_client_stop(NetClientState *nc)
> > +{
> > +    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> > +    struct vhost_dev *dev;
> > +
> > +    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
> > +
> > +    dev = s->vhost_vdpa.dev;
> > +    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
> > +        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
> > +    }
> > +}
> > +
> >  static NetClientInfo net_vhost_vdpa_info = {
> >          .type = NET_CLIENT_DRIVER_VHOST_VDPA,
> >          .size = sizeof(VhostVDPAState),
> >          .receive = vhost_vdpa_receive,
> > +        .start = vhost_vdpa_net_data_start,
> > +        .stop = vhost_vdpa_net_client_stop,
> >          .cleanup = vhost_vdpa_cleanup,
> >          .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
> >          .has_ufo = vhost_vdpa_has_ufo,
> > @@ -351,7 +401,7 @@ dma_map_err:
> >
> >  static int vhost_vdpa_net_cvq_start(NetClientState *nc)
> >  {
> > -    VhostVDPAState *s;
> > +    VhostVDPAState *s, *s0;
> >      struct vhost_vdpa *v;
> >      uint64_t backend_features;
> >      int64_t cvq_group;
> > @@ -415,8 +465,6 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
> >          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;
> >
> > @@ -425,6 +473,15 @@ out:
> >          return 0;
> >      }
> >
> > +    s0 = vhost_vdpa_net_first_nc_vdpa(s);
> > +    if (s0->vhost_vdpa.iova_tree) {
> > +        /* SVQ is already configured for all virtqueues */
> > +        v->iova_tree = s0->vhost_vdpa.iova_tree;
> > +    } else {
> > +        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
> > +                                           v->iova_range.last);
> > +    }
> > +
> >      r = vhost_vdpa_cvq_map_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer,
> >                                 vhost_vdpa_net_cvq_cmd_page_len(), false);
> >      if (unlikely(r < 0)) {
> > @@ -449,15 +506,9 @@ 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);
> > -        }
> >      }
> > +
> > +    vhost_vdpa_net_client_stop(nc);
> >  }
> >
> >  static ssize_t vhost_vdpa_net_cvq_add(VhostVDPAState *s, size_t out_len,
> > @@ -667,8 +718,7 @@ static NetClientState 
> > *net_vhost_vdpa_init(NetClientState *peer,
> >                                         int nvqs,
> >                                         bool is_datapath,
> >                                         bool svq,
> > -                                       struct vhost_vdpa_iova_range 
> > iova_range,
> > -                                       VhostIOVATree *iova_tree)
> > +                                       struct vhost_vdpa_iova_range 
> > iova_range)
> >  {
> >      NetClientState *nc = NULL;
> >      VhostVDPAState *s;
> > @@ -690,7 +740,6 @@ static NetClientState 
> > *net_vhost_vdpa_init(NetClientState *peer,
> >      s->vhost_vdpa.shadow_vqs_enabled = svq;
> >      s->vhost_vdpa.iova_range = iova_range;
> >      s->vhost_vdpa.shadow_data = svq;
> > -    s->vhost_vdpa.iova_tree = iova_tree;
> >      if (!is_datapath) {
> >          s->cvq_cmd_out_buffer = qemu_memalign(qemu_real_host_page_size(),
> >                                              
> > vhost_vdpa_net_cvq_cmd_page_len());
> > @@ -760,7 +809,6 @@ int net_init_vhost_vdpa(const Netdev *netdev, const 
> > char *name,
> >      uint64_t features;
> >      int vdpa_device_fd;
> >      g_autofree NetClientState **ncs = NULL;
> > -    g_autoptr(VhostIOVATree) iova_tree = NULL;
> >      struct vhost_vdpa_iova_range iova_range;
> >      NetClientState *nc;
> >      int queue_pairs, r, i = 0, has_cvq = 0;
> > @@ -812,12 +860,8 @@ int net_init_vhost_vdpa(const Netdev *netdev, const 
> > char *name,
> >          goto err;
> >      }
> >
> > -    if (opts->x_svq) {
> > -        if (!vhost_vdpa_net_valid_svq_features(features, errp)) {
> > -            goto err_svq;
> > -        }
> > -
> > -        iova_tree = vhost_iova_tree_new(iova_range.first, iova_range.last);
> > +    if (opts->x_svq && !vhost_vdpa_net_valid_svq_features(features, errp)) 
> > {
> > +        goto err;
> >      }
> >
> >      ncs = g_malloc0(sizeof(*ncs) * queue_pairs);
> > @@ -825,7 +869,7 @@ 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_range, iova_tree);
> > +                                     iova_range);
> >          if (!ncs[i])
> >              goto err;
> >      }
> > @@ -833,13 +877,11 @@ int net_init_vhost_vdpa(const Netdev *netdev, const 
> > char *name,
> >      if (has_cvq) {
> >          nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> >                                   vdpa_device_fd, i, 1, false,
> > -                                 opts->x_svq, iova_range, iova_tree);
> > +                                 opts->x_svq, iova_range);
> >          if (!nc)
> >              goto err;
> >      }
> >
> > -    /* iova_tree ownership belongs to last NetClientState */
> > -    g_steal_pointer(&iova_tree);
> >      return 0;
> >
> >  err:
> > @@ -849,7 +891,6 @@ err:
> >          }
> >      }
> >
> > -err_svq:
> >      qemu_close(vdpa_device_fd);
> >
> >      return -1;
> > --
> > 2.31.1
> >
>