virtio-net: Added eBPF RSS to virtio-net.

When RSS is enabled the device tries to load the eBPF program
to select RX virtqueue in the TUN. If eBPF can be loaded
the RSS will function also with vhost (works with kernel 5.8 and later).
Software RSS is used as a fallback with vhost=off when eBPF can't be loaded
or when hash population requested by the guest.

Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

2 files changed, 116 insertions, 3 deletions

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 24d555e764..44c1ed92dc 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -45,6 +45,7 @@ static const int kernel_feature_bits[] = {
     VIRTIO_NET_F_MTU,
     VIRTIO_F_IOMMU_PLATFORM,
     VIRTIO_F_RING_PACKED,
+    VIRTIO_NET_F_HASH_REPORT,
     VHOST_INVALID_FEATURE_BIT
 };
 
@@ -71,6 +72,8 @@ static const int user_feature_bits[] = {
     VIRTIO_NET_F_MTU,
     VIRTIO_F_IOMMU_PLATFORM,
     VIRTIO_F_RING_PACKED,
+    VIRTIO_NET_F_RSS,
+    VIRTIO_NET_F_HASH_REPORT,
 
     /* This bit implies RARP isn't sent by QEMU out of band */
     VIRTIO_NET_F_GUEST_ANNOUNCE,
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 6b7e8dd04e..613be072c3 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -737,8 +737,9 @@ static uint64_t virtio_net_get_features(VirtIODevice *vdev, uint64_t features,
         return features;
     }
 
-    virtio_clear_feature(&features, VIRTIO_NET_F_RSS);
-    virtio_clear_feature(&features, VIRTIO_NET_F_HASH_REPORT);
+    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;
 
@@ -1163,12 +1164,79 @@ static int virtio_net_handle_announce(VirtIONet *n, uint8_t cmd,
     }
 }
 
+static void virtio_net_detach_epbf_rss(VirtIONet *n);
+
 static void virtio_net_disable_rss(VirtIONet *n)
 {
     if (n->rss_data.enabled) {
         trace_virtio_net_rss_disable();
     }
     n->rss_data.enabled = false;
+
+    virtio_net_detach_epbf_rss(n);
+}
+
+static bool virtio_net_attach_ebpf_to_backend(NICState *nic, int prog_fd)
+{
+    NetClientState *nc = qemu_get_peer(qemu_get_queue(nic), 0);
+    if (nc == NULL || nc->info->set_steering_ebpf == NULL) {
+        return false;
+    }
+
+    return nc->info->set_steering_ebpf(nc, prog_fd);
+}
+
+static void rss_data_to_rss_config(struct VirtioNetRssData *data,
+                                   struct EBPFRSSConfig *config)
+{
+    config->redirect = data->redirect;
+    config->populate_hash = data->populate_hash;
+    config->hash_types = data->hash_types;
+    config->indirections_len = data->indirections_len;
+    config->default_queue = data->default_queue;
+}
+
+static bool virtio_net_attach_epbf_rss(VirtIONet *n)
+{
+    struct EBPFRSSConfig config = {};
+
+    if (!ebpf_rss_is_loaded(&n->ebpf_rss)) {
+        return false;
+    }
+
+    rss_data_to_rss_config(&n->rss_data, &config);
+
+    if (!ebpf_rss_set_all(&n->ebpf_rss, &config,
+                          n->rss_data.indirections_table, n->rss_data.key)) {
+        return false;
+    }
+
+    if (!virtio_net_attach_ebpf_to_backend(n->nic, n->ebpf_rss.program_fd)) {
+        return false;
+    }
+
+    return true;
+}
+
+static void virtio_net_detach_epbf_rss(VirtIONet *n)
+{
+    virtio_net_attach_ebpf_to_backend(n->nic, -1);
+}
+
+static bool virtio_net_load_ebpf(VirtIONet *n)
+{
+    if (!virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
+        /* backend does't support steering ebpf */
+        return false;
+    }
+
+    return ebpf_rss_load(&n->ebpf_rss);
+}
+
+static void virtio_net_unload_ebpf(VirtIONet *n)
+{
+    virtio_net_attach_ebpf_to_backend(n->nic, -1);
+    ebpf_rss_unload(&n->ebpf_rss);
 }
 
 static uint16_t virtio_net_handle_rss(VirtIONet *n,
@@ -1283,6 +1351,25 @@ static uint16_t virtio_net_handle_rss(VirtIONet *n,
         goto error;
     }
     n->rss_data.enabled = true;
+
+    if (!n->rss_data.populate_hash) {
+        if (!virtio_net_attach_epbf_rss(n)) {
+            /* EBPF must be loaded for vhost */
+            if (get_vhost_net(qemu_get_queue(n->nic)->peer)) {
+                warn_report("Can't load eBPF RSS for vhost");
+                goto error;
+            }
+            /* fallback to software RSS */
+            warn_report("Can't load eBPF RSS - fallback to software RSS");
+            n->rss_data.enabled_software_rss = true;
+        }
+    } else {
+        /* use software RSS for hash populating */
+        /* and detach eBPF if was loaded before */
+        virtio_net_detach_epbf_rss(n);
+        n->rss_data.enabled_software_rss = true;
+    }
+
     trace_virtio_net_rss_enable(n->rss_data.hash_types,
                                 n->rss_data.indirections_len,
                                 temp.b);
@@ -1668,7 +1755,7 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
         return -1;
     }
 
-    if (!no_rss && n->rss_data.enabled) {
+    if (!no_rss && n->rss_data.enabled && n->rss_data.enabled_software_rss) {
         int index = virtio_net_process_rss(nc, buf, size);
         if (index >= 0) {
             NetClientState *nc2 = qemu_get_subqueue(n->nic, index);
@@ -2772,6 +2859,19 @@ static int virtio_net_post_load_device(void *opaque, int version_id)
     }
 
     if (n->rss_data.enabled) {
+        n->rss_data.enabled_software_rss = n->rss_data.populate_hash;
+        if (!n->rss_data.populate_hash) {
+            if (!virtio_net_attach_epbf_rss(n)) {
+                if (get_vhost_net(qemu_get_queue(n->nic)->peer)) {
+                    warn_report("Can't post-load eBPF RSS for vhost");
+                } else {
+                    warn_report("Can't post-load eBPF RSS - "
+                                "fallback to software RSS");
+                    n->rss_data.enabled_software_rss = true;
+                }
+            }
+        }
+
         trace_virtio_net_rss_enable(n->rss_data.hash_types,
                                     n->rss_data.indirections_len,
                                     sizeof(n->rss_data.key));
@@ -3352,6 +3452,10 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
     n->qdev = dev;
 
     net_rx_pkt_init(&n->rx_pkt, false);
+
+    if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
+        virtio_net_load_ebpf(n);
+    }
 }
 
 static void virtio_net_device_unrealize(DeviceState *dev)
@@ -3360,6 +3464,10 @@ static void virtio_net_device_unrealize(DeviceState *dev)
     VirtIONet *n = VIRTIO_NET(dev);
     int i, max_queues;
 
+    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);
 
@@ -3402,6 +3510,8 @@ static void virtio_net_instance_init(Object *obj)
     device_add_bootindex_property(obj, &n->nic_conf.bootindex,
                                   "bootindex", "/ethernet-phy@0",
                                   DEVICE(n));
+
+    ebpf_rss_init(&n->ebpf_rss);
 }
 
 static int virtio_net_pre_save(void *opaque)