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

[Eugenio Perez Martin]

On Mon, Jan 16, 2023 at 4:05 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2023/1/13 15:28, Eugenio Perez Martin 写道:
> > 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.
>
>
> Ok.
>
>
> >
> > 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?
>
>
> Kind of, but I think we can leave the code as is.
>
> In the future, as discussed, we need to introduce something like a
> parent or opaque structure for NetClientState structure, it can simply a
> lot of things: we can have one same common parent for all queues, then
> there's no need for the trick like first_nc_iova_tree() and other
> similar tricks.
>

So we can ack this patch or you prefer to explore the change for the
next series?

Thanks!

> Thanks
>
> >
> > 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
> >>>
>