virtio-net: Added property to load eBPF RSS with fds.

eBPF RSS program and maps may now be passed during initialization.
Initially was implemented for libvirt to launch qemu without permissions,
and initialized eBPF program through the helper.

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

hw/net/virtio-net.c

@@ -42,6 +42,7 @@
 #include "sysemu/sysemu.h"
 #include "trace.h"
 #include "monitor/qdev.h"
+#include "monitor/monitor.h"
 #include "hw/pci/pci_device.h"
 #include "net_rx_pkt.h"
 #include "hw/virtio/vhost.h"
@@ -1327,14 +1328,55 @@ 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)
+static bool virtio_net_load_ebpf_fds(VirtIONet *n, Error **errp)
 {
-    if (!virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
-        /* backend does't support steering ebpf */
-        return false;
+    int fds[EBPF_RSS_MAX_FDS] = { [0 ... EBPF_RSS_MAX_FDS - 1] = -1};
+    int nfds = 0;
+    int ret = true;
+    int i = 0;
+    g_auto(GStrv) fds_strs = g_strsplit(n->ebpf_rss_fds, ":", 0);
+
+    ERRP_GUARD();
+
+    if (g_strv_length(fds_strs) != EBPF_RSS_MAX_FDS) {
+        error_setg(errp,
+                  "Expected %d file descriptors but got %d",
+                  EBPF_RSS_MAX_FDS, g_strv_length(fds_strs));
+       return false;
+   }
+
+    for (i = 0; i < nfds; i++) {
+        fds[i] = monitor_fd_param(monitor_cur(), fds_strs[i], errp);
+        if (*errp) {
+            ret = false;
+            goto exit;
+        }
+    }
+
+    ret = ebpf_rss_load_fds(&n->ebpf_rss, fds[0], fds[1], fds[2], fds[3]);
+
+exit:
+    if (!ret || *errp) {
+        for (i = 0; i < nfds && fds[i] != -1; i++) {
+            close(fds[i]);
+        }
     }
 
-    return ebpf_rss_load(&n->ebpf_rss);
+    return ret;
+}
+
+static bool virtio_net_load_ebpf(VirtIONet *n, Error **errp)
+{
+    bool ret = false;
+
+    if (virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
+        if (!(n->ebpf_rss_fds
+                && virtio_net_load_ebpf_fds(n, errp))) {
+            ret = ebpf_rss_load(&n->ebpf_rss);
+        }
+    }
+
+    return ret;
 }
 
 static void virtio_net_unload_ebpf(VirtIONet *n)
@@ -3764,7 +3806,7 @@ 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);
+        virtio_net_load_ebpf(n, errp);
     }
 }
 
@@ -3926,6 +3968,7 @@ static Property virtio_net_properties[] = {
                     VIRTIO_NET_F_RSS, false),
     DEFINE_PROP_BIT64("hash", VirtIONet, host_features,
                     VIRTIO_NET_F_HASH_REPORT, false),
+    DEFINE_PROP_STRING("ebpf_rss_fds", VirtIONet, ebpf_rss_fds),
     DEFINE_PROP_BIT64("guest_rsc_ext", VirtIONet, host_features,
                     VIRTIO_NET_F_RSC_EXT, false),
     DEFINE_PROP_UINT32("rsc_interval", VirtIONet, rsc_timeout,

include/hw/virtio/virtio-net.h

@@ -219,6 +219,7 @@ struct VirtIONet {
     VirtioNetRssData rss_data;
     struct NetRxPkt *rx_pkt;
     struct EBPFRSSContext ebpf_rss;
+    char *ebpf_rss_fds;
 };
 
 size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,