[RFC v2 05/13] vdpa net: add migration blocker if cannot migrate cvq

[Eugenio Pérez]

A vdpa net device must initialize with SVQ in order to be migratable,
and initialization code verifies conditions.  If the device is not
initialized with the x-svq parameter, it will not expose _F_LOG so vhost
sybsystem will block VM migration from its initialization.

Next patches change this. Net data VQs will be shadowed only at
migration time and vdpa net devices need to expose _F_LOG as long as it
can go to SVQ.

Since we don't know that at initialization time but at start, add an
independent blocker at CVQ.

Signed-off-by: Eugenio Pérez <epere...@redhat.com>
---
 net/vhost-vdpa.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 631424d9c4..2ca93e850a 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -26,12 +26,14 @@
 #include <err.h>
 #include "standard-headers/linux/virtio_net.h"
 #include "monitor/monitor.h"
+#include "migration/blocker.h"
 #include "hw/virtio/vhost.h"
 
 /* Todo:need to add the multiqueue support here */
 typedef struct VhostVDPAState {
     NetClientState nc;
     struct vhost_vdpa vhost_vdpa;
+    Error *migration_blocker;
     VHostNetState *vhost_net;
 
     /* Control commands shadow buffers */
@@ -433,9 +435,15 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
             g_strerror(errno), errno);
         return -1;
     }
-    if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID)) ||
-        !vhost_vdpa_net_valid_svq_features(v->dev->features, NULL)) {
-        return 0;
+    if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID))) {
+        error_setg(&s->migration_blocker,
+                   "vdpa device %s does not support ASID",
+                   nc->name);
+        goto out;
+    }
+    if (!vhost_vdpa_net_valid_svq_features(v->dev->features,
+                                           &s->migration_blocker)) {
+        goto out;
     }
 
     /*
@@ -455,7 +463,10 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
         }
 
         if (group == cvq_group) {
-            return 0;
+            error_setg(&s->migration_blocker,
+                "vdpa %s vq %d group %"PRId64" is the same as cvq group "
+                "%"PRId64, nc->name, i, group, cvq_group);
+            goto out;
         }
     }
 
@@ -468,8 +479,15 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
     s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_ASID;
 
 out:
-    if (!s->vhost_vdpa.shadow_vqs_enabled) {
-        return 0;
+    if (s->migration_blocker) {
+        Error *errp = NULL;
+        r = migrate_add_blocker(s->migration_blocker, &errp);
+        if (unlikely(r != 0)) {
+            g_clear_pointer(&s->migration_blocker, error_free);
+            error_report_err(errp);
+        }
+
+        return r;
     }
 
     s0 = vhost_vdpa_net_first_nc_vdpa(s);
@@ -513,6 +531,11 @@ static void vhost_vdpa_net_cvq_stop(NetClientState *nc)
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
     }
 
+    if (s->migration_blocker) {
+        migrate_del_blocker(s->migration_blocker);
+        g_clear_pointer(&s->migration_blocker, error_free);
+    }
+
     vhost_vdpa_net_client_stop(nc);
 }
 
-- 
2.31.1