[PATCH v9 13/20] virtio-net: Return an error when vhost cannot enable RSS

[Akihiko Odaki <akihiko.odaki@daynix.com>]

vhost requires eBPF for RSS. When eBPF is not available, virtio-net
implicitly disables RSS even if the user explicitly requests it. Return
an error instead of implicitly disabling RSS if RSS is requested but not
available.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 hw/net/virtio-net.c | 97 ++++++++++++++++++++++++++---------------------------
 1 file changed, 48 insertions(+), 49 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 61b49e335dea..3d53eba88cfc 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -793,9 +793,6 @@ static uint64_t virtio_net_get_features(VirtIODevice *vdev, uint64_t features,
         return features;
     }
 
-    if (!ebpf_rss_is_loaded(&n->ebpf_rss)) {
-        virtio_clear_feature(&features, VIRTIO_NET_F_RSS);
-    }
     features = vhost_net_get_features(get_vhost_net(nc->peer), features);
     vdev->backend_features = features;
 
@@ -3591,6 +3588,50 @@ static bool failover_hide_primary_device(DeviceListener *listener,
     return qatomic_read(&n->failover_primary_hidden);
 }
 
+static void virtio_net_device_unrealize(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VirtIONet *n = VIRTIO_NET(dev);
+    int i, max_queue_pairs;
+
+    if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
+        virtio_net_unload_ebpf(n);
+    }
+
+    /* This will stop vhost backend if appropriate. */
+    virtio_net_set_status(vdev, 0);
+
+    g_free(n->netclient_name);
+    n->netclient_name = NULL;
+    g_free(n->netclient_type);
+    n->netclient_type = NULL;
+
+    g_free(n->mac_table.macs);
+    g_free(n->vlans);
+
+    if (n->failover) {
+        qobject_unref(n->primary_opts);
+        device_listener_unregister(&n->primary_listener);
+        migration_remove_notifier(&n->migration_state);
+    } else {
+        assert(n->primary_opts == NULL);
+    }
+
+    max_queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
+    for (i = 0; i < max_queue_pairs; i++) {
+        virtio_net_del_queue(n, i);
+    }
+    /* delete also control vq */
+    virtio_del_queue(vdev, max_queue_pairs * 2);
+    qemu_announce_timer_del(&n->announce_timer, false);
+    g_free(n->vqs);
+    qemu_del_nic(n->nic);
+    virtio_net_rsc_cleanup(n);
+    g_free(n->rss_data.indirections_table);
+    net_rx_pkt_uninit(n->rx_pkt);
+    virtio_cleanup(vdev);
+}
+
 static void virtio_net_device_realize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
@@ -3760,53 +3801,11 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
 
     net_rx_pkt_init(&n->rx_pkt);
 
-    if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
-        virtio_net_load_ebpf(n);
-    }
-}
-
-static void virtio_net_device_unrealize(DeviceState *dev)
-{
-    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
-    VirtIONet *n = VIRTIO_NET(dev);
-    int i, max_queue_pairs;
-
-    if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
-        virtio_net_unload_ebpf(n);
+    if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS) &&
+        !virtio_net_load_ebpf(n) && get_vhost_net(nc->peer)) {
+        virtio_net_device_unrealize(dev);
+        error_setg(errp, "Can't load eBPF RSS for vhost");
     }
-
-    /* This will stop vhost backend if appropriate. */
-    virtio_net_set_status(vdev, 0);
-
-    g_free(n->netclient_name);
-    n->netclient_name = NULL;
-    g_free(n->netclient_type);
-    n->netclient_type = NULL;
-
-    g_free(n->mac_table.macs);
-    g_free(n->vlans);
-
-    if (n->failover) {
-        qobject_unref(n->primary_opts);
-        device_listener_unregister(&n->primary_listener);
-        migration_remove_notifier(&n->migration_state);
-    } else {
-        assert(n->primary_opts == NULL);
-    }
-
-    max_queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
-    for (i = 0; i < max_queue_pairs; i++) {
-        virtio_net_del_queue(n, i);
-    }
-    /* delete also control vq */
-    virtio_del_queue(vdev, max_queue_pairs * 2);
-    qemu_announce_timer_del(&n->announce_timer, false);
-    g_free(n->vqs);
-    qemu_del_nic(n->nic);
-    virtio_net_rsc_cleanup(n);
-    g_free(n->rss_data.indirections_table);
-    net_rx_pkt_uninit(n->rx_pkt);
-    virtio_cleanup(vdev);
 }
 
 static void virtio_net_reset(VirtIODevice *vdev)

-- 
2.44.0