[RFC v2 11/13] vdpa: add vdpa net migration state notifier

[Eugenio Pérez]

This allows net to restart the device backend to configure SVQ on it.

Ideally, these changes should not be net specific. However, the vdpa net
backend is the one with enough knowledge to configure everything because
of some reasons:
* Queues might need to be shadowed or not depending on its kind (control
  vs data).
* Queues need to share the same map translations (iova tree).

Because of that it is cleaner to restart the whole net backend and
configure again as expected, similar to how vhost-kernel moves between
userspace and passthrough.

If more kinds of devices need dynamic switching to SVQ we can create a
callback struct like VhostOps and move most of the code there.
VhostOps cannot be reused since all vdpa backend share them, and to
personalize just for networking would be too heavy.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 net/vhost-vdpa.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 5d7ad6e4d7..f38532b1df 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -26,6 +26,8 @@
 #include <err.h>
 #include "standard-headers/linux/virtio_net.h"
 #include "monitor/monitor.h"
+#include "migration/migration.h"
+#include "migration/misc.h"
 #include "migration/blocker.h"
 #include "hw/virtio/vhost.h"
 
@@ -33,6 +35,7 @@
 typedef struct VhostVDPAState {
     NetClientState nc;
     struct vhost_vdpa vhost_vdpa;
+    Notifier migration_state;
     Error *migration_blocker;
     VHostNetState *vhost_net;
 
@@ -243,10 +246,86 @@ static VhostVDPAState 
*vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
     return DO_UPCAST(VhostVDPAState, nc, nc0);
 }
 
+static void vhost_vdpa_net_log_global_enable(VhostVDPAState *s, bool enable)
+{
+    struct vhost_vdpa *v = &s->vhost_vdpa;
+    VirtIONet *n;
+    VirtIODevice *vdev;
+    int data_queue_pairs, cvq, r;
+    NetClientState *peer;
+
+    /* We are only called on the first data vqs and only if x-svq is not set */
+    if (s->vhost_vdpa.shadow_vqs_enabled == enable) {
+        return;
+    }
+
+    vdev = v->dev->vdev;
+    n = VIRTIO_NET(vdev);
+    if (!n->vhost_started) {
+        return;
+    }
+
+    if (enable) {
+        ioctl(v->device_fd, VHOST_VDPA_SUSPEND);
+    }
+    data_queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
+    cvq = virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) ?
+                                  n->max_ncs - n->max_queue_pairs : 0;
+    vhost_net_stop(vdev, n->nic->ncs, data_queue_pairs, cvq);
+
+    peer = s->nc.peer;
+    for (int i = 0; i < data_queue_pairs + cvq; i++) {
+        VhostVDPAState *vdpa_state;
+        NetClientState *nc;
+
+        if (i < data_queue_pairs) {
+            nc = qemu_get_peer(peer, i);
+        } else {
+            nc = qemu_get_peer(peer, n->max_queue_pairs);
+        }
+
+        vdpa_state = DO_UPCAST(VhostVDPAState, nc, nc);
+        vdpa_state->vhost_vdpa.shadow_data = enable;
+
+        if (i < data_queue_pairs) {
+            /* Do not override CVQ shadow_vqs_enabled */
+            vdpa_state->vhost_vdpa.shadow_vqs_enabled = enable;
+        }
+    }
+
+    r = vhost_net_start(vdev, n->nic->ncs, data_queue_pairs, cvq);
+    if (unlikely(r < 0)) {
+        error_report("unable to start vhost net: %s(%d)", g_strerror(-r), -r);
+    }
+}
+
+static void vdpa_net_migration_state_notifier(Notifier *notifier, void *data)
+{
+    MigrationState *migration = data;
+    VhostVDPAState *s = container_of(notifier, VhostVDPAState,
+                                     migration_state);
+
+    switch (migration->state) {
+    case MIGRATION_STATUS_SETUP:
+        vhost_vdpa_net_log_global_enable(s, true);
+        return;
+
+    case MIGRATION_STATUS_CANCELLING:
+    case MIGRATION_STATUS_CANCELLED:
+    case MIGRATION_STATUS_FAILED:
+        vhost_vdpa_net_log_global_enable(s, false);
+        return;
+    };
+}
+
 static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
 {
     struct vhost_vdpa *v = &s->vhost_vdpa;
 
+    if (v->feature_log) {
+        add_migration_state_change_notifier(&s->migration_state);
+    }
+
     if (v->shadow_vqs_enabled) {
         v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
                                            v->iova_range.last);
@@ -280,6 +359,10 @@ static void vhost_vdpa_net_client_stop(NetClientState *nc)
 
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
 
+    if (s->vhost_vdpa.index == 0 && s->vhost_vdpa.feature_log) {
+        remove_migration_state_change_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.iova_tree, vhost_iova_tree_delete);
@@ -767,6 +850,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState 
*peer,
     s->vhost_vdpa.device_fd = vdpa_device_fd;
     s->vhost_vdpa.index = queue_pair_index;
     s->always_svq = svq;
+    s->migration_state.notify = vdpa_net_migration_state_notifier;
     s->vhost_vdpa.shadow_vqs_enabled = svq;
     s->vhost_vdpa.iova_range = iova_range;
     s->vhost_vdpa.shadow_data = svq;
-- 
2.31.1