[PATCH v6 12/21] virtio-net: Enable software RSS

[Akihiko Odaki]

virtio-net implements software RSS but does not enable it. Enable it
when RSS is requested, but the eBPF implementation is not available.
We also check if vhost is in use in such a case since software RSS is
incompatible with vhost. A warning will be emitted when falling back to
software RSS since it provides no performance benefit.

Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
---
 hw/net/virtio-net.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 7bb91617d0..1fa020d905 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1260,10 +1260,12 @@ static bool virtio_net_attach_epbf_rss(VirtIONet *n)
 
     if (!ebpf_rss_set_all(&n->ebpf_rss, &config,
                           n->rss_data.indirections_table, n->rss_data.key)) {
+        warn_report("Failed to configure eBPF RSS");
         return false;
     }
 
     if (!virtio_net_attach_ebpf_to_backend(n->nic, n->ebpf_rss.program_fd)) {
+        warn_report("Failed to attach eBPF to backend");
         return false;
     }
 
@@ -1278,16 +1280,10 @@ static void virtio_net_detach_epbf_rss(VirtIONet *n)
 static void virtio_net_commit_rss_config(VirtIONet *n)
 {
     if (n->rss_data.enabled) {
-        n->rss_data.enabled_software_rss = n->rss_data.populate_hash;
+        n->rss_data.enabled_software_rss = n->rss_data.populate_hash ||
+                                           !virtio_net_attach_epbf_rss(n);
         if (n->rss_data.populate_hash) {
             virtio_net_detach_epbf_rss(n);
-        } else if (!virtio_net_attach_epbf_rss(n)) {
-            if (get_vhost_net(qemu_get_queue(n->nic)->peer)) {
-                warn_report("Can't load eBPF RSS for vhost");
-            } else {
-                warn_report("Can't load eBPF RSS - fallback to software RSS");
-                n->rss_data.enabled_software_rss = true;
-            }
         }
 
         trace_virtio_net_rss_enable(n->rss_data.hash_types,
@@ -3747,8 +3743,13 @@ static void virtio_net_device_realize(DeviceState *dev, 
Error **errp)
 
     if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS) &&
         !virtio_net_load_ebpf(n)) {
-        error_setg(errp, "Can't load eBPF RSS");
-        virtio_net_device_unrealize(dev);
+        if (get_vhost_net(nc->peer)) {
+            error_setg(errp, "Can't load eBPF RSS for vhost");
+            virtio_net_device_unrealize(dev);
+            return;
+        }
+
+        warn_report_once("Can't load eBPF RSS - fallback to software RSS");
     }
 }
 
-- 
2.42.0