[PATCH v4 12/15] vdpa: block migration if device has unsupported features

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

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

Next patches change this, so we need to verify migration conditions
differently.

QEMU only supports a subset of net features in SVQ, and it cannot
migrate state that cannot track or restore in the destination.  Add a
migration blocker if the device offer an unsupported feature.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v3: add mirgation blocker properly so vhost_dev can handle it.
---
 net/vhost-vdpa.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 4f983df000..094dc1c2d0 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -795,7 +795,8 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
                                        int nvqs,
                                        bool is_datapath,
                                        bool svq,
-                                       struct vhost_vdpa_iova_range iova_range)
+                                       struct vhost_vdpa_iova_range iova_range,
+                                       uint64_t features)
 {
     NetClientState *nc = NULL;
     VhostVDPAState *s;
@@ -818,7 +819,10 @@ 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;
-    if (!is_datapath) {
+    if (queue_pair_index == 0) {
+        vhost_vdpa_net_valid_svq_features(features,
+                                          &s->vhost_vdpa.migration_blocker);
+    } else if (!is_datapath) {
         s->cvq_cmd_out_buffer = qemu_memalign(qemu_real_host_page_size(),
                                             vhost_vdpa_net_cvq_cmd_page_len());
         memset(s->cvq_cmd_out_buffer, 0, vhost_vdpa_net_cvq_cmd_page_len());
@@ -956,7 +960,7 @@ 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_range, features);
         if (!ncs[i])
             goto err;
     }
@@ -964,7 +968,7 @@ 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);
+                                 opts->x_svq, iova_range, features);
         if (!nc)
             goto err;
     }
-- 
2.31.1