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

[Jason Wang]

在 2023/1/13 15:28, Eugenio Perez Martin 写道:
On Fri, Jan 13, 2023 at 4:53 AM Jason Wang <jasow...@redhat.com> wrote:
On Fri, Jan 13, 2023 at 1:24 AM Eugenio Pérez <epere...@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 <epere...@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.

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