[PATCH v2 6/7] vdpa: move iova_tree allocation to net_vhost_vdpa_init

["Eugenio Pérez" <eperezma@redhat.com>]

As we are moving to keep the mapping through all the vdpa device life
instead of resetting it at VirtIO reset, we need to move all its
dependencies to the initialization too.  In particular devices with
x-svq=on need a valid iova_tree from the beginning.

Simplify the code also consolidating the two creation points: the first
data vq in case of SVQ active and CVQ start in case only CVQ uses it.

Suggested-by: Si-Wei Liu <si-wei.liu@oracle.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/hw/virtio/vhost-vdpa.h | 16 ++++++++++++++-
 net/vhost-vdpa.c               | 36 +++-------------------------------
 2 files changed, 18 insertions(+), 34 deletions(-)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index 03ed2f2be3..ad754eb803 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -37,7 +37,21 @@ typedef struct vhost_vdpa_shared {
     struct vhost_vdpa_iova_range iova_range;
     QLIST_HEAD(, vdpa_iommu) iommu_list;
 
-    /* IOVA mapping used by the Shadow Virtqueue */
+    /*
+     * IOVA mapping used by the Shadow Virtqueue
+     *
+     * It is shared among all ASID for simplicity, whether CVQ shares ASID with
+     * guest or not:
+     * - Memory listener need access to guest's memory addresses allocated in
+     *   the IOVA tree.
+     * - There should be plenty of IOVA address space for both ASID not to
+     *   worry about collisions between them.  Guest's translations are still
+     *   validated with virtio virtqueue_pop so there is no risk for the guest
+     *   to access memory that it shouldn't.
+     *
+     * To allocate a iova tree per ASID is doable but it complicates the code
+     * and it is not worth it for the moment.
+     */
     VhostIOVATree *iova_tree;
 
     /* Copy of backend features */
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index cc589dd148..57edcf34d0 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -232,6 +232,7 @@ static void vhost_vdpa_cleanup(NetClientState *nc)
         return;
     }
     qemu_close(s->vhost_vdpa.shared->device_fd);
+    g_clear_pointer(&s->vhost_vdpa.shared->iova_tree, vhost_iova_tree_delete);
     g_free(s->vhost_vdpa.shared);
 }
 
@@ -329,16 +330,8 @@ static void vdpa_net_migration_state_notifier(Notifier *notifier, void *data)
 
 static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
 {
-    struct vhost_vdpa *v = &s->vhost_vdpa;
-
     migration_add_notifier(&s->migration_state,
                            vdpa_net_migration_state_notifier);
-
-    /* iova_tree may be initialized by vhost_vdpa_net_load_setup */
-    if (v->shadow_vqs_enabled && !v->shared->iova_tree) {
-        v->shared->iova_tree = vhost_iova_tree_new(v->shared->iova_range.first,
-                                                   v->shared->iova_range.last);
-    }
 }
 
 static int vhost_vdpa_net_data_start(NetClientState *nc)
@@ -383,19 +376,12 @@ static int vhost_vdpa_net_data_load(NetClientState *nc)
 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);
 
     if (s->vhost_vdpa.index == 0) {
         migration_remove_notifier(&s->migration_state);
     }
-
-    dev = s->vhost_vdpa.dev;
-    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
-        g_clear_pointer(&s->vhost_vdpa.shared->iova_tree,
-                        vhost_iova_tree_delete);
-    }
 }
 
 static NetClientInfo net_vhost_vdpa_info = {
@@ -557,24 +543,6 @@ out:
         return 0;
     }
 
-    /*
-     * If other vhost_vdpa already have an iova_tree, reuse it for simplicity,
-     * whether CVQ shares ASID with guest or not, because:
-     * - Memory listener need access to guest's memory addresses allocated in
-     *   the IOVA tree.
-     * - There should be plenty of IOVA address space for both ASID not to
-     *   worry about collisions between them.  Guest's translations are still
-     *   validated with virtio virtqueue_pop so there is no risk for the guest
-     *   to access memory that it shouldn't.
-     *
-     * To allocate a iova tree per ASID is doable but it complicates the code
-     * and it is not worth it for the moment.
-     */
-    if (!v->shared->iova_tree) {
-        v->shared->iova_tree = vhost_iova_tree_new(v->shared->iova_range.first,
-                                                   v->shared->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)) {
@@ -1674,6 +1642,8 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
         s->vhost_vdpa.shared->device_fd = vdpa_device_fd;
         s->vhost_vdpa.shared->iova_range = iova_range;
         s->vhost_vdpa.shared->shadow_data = svq;
+        s->vhost_vdpa.shared->iova_tree = vhost_iova_tree_new(iova_range.first,
+                                                              iova_range.last);
     } else if (!is_datapath) {
         s->cvq_cmd_out_buffer = mmap(NULL, vhost_vdpa_net_cvq_cmd_page_len(),
                                      PROT_READ | PROT_WRITE,
-- 
2.43.0