net: Allow network backends to advertise max TX queue size

This commit refactors how the maximum transmit queue size for
virtio-net devices is determined, making the mechanism more generic
and extensible.

Previously, virtio_net_max_tx_queue_size() contained hardcoded
checks for specific network backend types (vhost-user and
vhost-vdpa) to determine their supported maximum queue size. This
created direct dependencies and would require modifications for
every new backend that supports variable queue sizes.

To improve flexibility, a new max_tx_queue_size field is added
to the vhost_net structure. This allows each network backend
to advertise its supported maximum transmit queue size directly.

The virtio_net_max_tx_queue_size() function now retrieves the max
TX queue size from the vhost_net struct, if available and set.
Otherwise, it defaults to VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 976d2b315a2fcef8a36a008253e16bb626956abe..74d2e3ed90f5ff5e3712ccad59d18238f787c16a 100644 (file)
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -245,6 +245,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     net->dev.nvqs = options->nvqs;
     net->feature_bits = options->feature_bits;
     net->save_acked_features = options->save_acked_features;
+    net->max_tx_queue_size = options->max_tx_queue_size;
 
     net->dev.max_queues = 1;
     net->dev.vqs = net->vqs;

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index e3400f18c8d64d27b074f600213991b3b1fccc85..39fc280839651d128880d223557619f40148eef7 100644 (file)
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -670,22 +670,22 @@ static void virtio_net_set_mrg_rx_bufs(VirtIONet *n, int mergeable_rx_bufs,
 static int virtio_net_max_tx_queue_size(VirtIONet *n)
 {
     NetClientState *peer = n->nic_conf.peers.ncs[0];
+    struct vhost_net *net;
 
-    /*
-     * Backends other than vhost-user or vhost-vdpa don't support max queue
-     * size.
-     */
     if (!peer) {
-        return VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;
+        goto default_value;
     }
 
-    switch(peer->info->type) {
-    case NET_CLIENT_DRIVER_VHOST_USER:
-    case NET_CLIENT_DRIVER_VHOST_VDPA:
-        return VIRTQUEUE_MAX_SIZE;
-    default:
-        return VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;
-    };
+    net = get_vhost_net(peer);
+
+    if (!net || !net->max_tx_queue_size) {
+        goto default_value;
+    }
+
+    return net->max_tx_queue_size;
+
+default_value:
+    return VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;
 }
 
 static int peer_attach(VirtIONet *n, int index)

diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index b0830bac798a0e2f1b262ef13938d6ba42093063..a62992c8192e88a094a120b350fbd48d8c262674 100644 (file)
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -145,6 +145,7 @@ struct vhost_net {
     struct vhost_virtqueue vqs[2];
     int backend;
     const int *feature_bits;
+    int max_tx_queue_size;
     SaveAcketFeatures *save_acked_features;
     NetClientState *nc;
 };

diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index eb26ed9bdcbff1dd183a8aa450150c03aed5c39a..8f4fddfb69eae0c30946b5968d5cd9bf85f4cad8 100644 (file)
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -16,6 +16,7 @@ typedef struct VhostNetOptions {
     uint32_t busyloop_timeout;
     unsigned int nvqs;
     const int *feature_bits;
+    int max_tx_queue_size;
     GetAckedFeatures *get_acked_features;
     SaveAcketFeatures *save_acked_features;
     void *opaque;

diff --git a/net/tap.c b/net/tap.c
index 79fa02a65c9124b163a9bd4f9a68f3d7be90d6a4..2f0cb55c9a772898245f4b90e5b39a809a7b4ae4 100644 (file)
--- a/net/tap.c
+++ b/net/tap.c
@@ -746,6 +746,7 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
         options.feature_bits = kernel_feature_bits;
         options.get_acked_features = NULL;
         options.save_acked_features = NULL;
+        options.max_tx_queue_size = 0;
 
         s->vhost_net = vhost_net_init(&options);
         if (!s->vhost_net) {

diff --git a/net/vhost-user.c b/net/vhost-user.c
index 8a3df27b02cf54df2b079ffbb38f91743cfe4298..bf892915def1e3e5a95d28b385251608788fe729 100644 (file)
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -138,6 +138,7 @@ static int vhost_user_start(int queues, NetClientState *ncs[],
         options.busyloop_timeout = 0;
         options.nvqs = 2;
         options.feature_bits = user_feature_bits;
+        options.max_tx_queue_size = VIRTQUEUE_MAX_SIZE;
         options.get_acked_features = vhost_user_get_acked_features;
         options.save_acked_features = vhost_user_save_acked_features;
 

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index c63225d3d2edc11f59a346d59cc6c80b1b2f0dbc..353392b3d7418e3634ae54167f895943a5f1d862 100644 (file)
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -204,6 +204,7 @@ static int vhost_vdpa_add(NetClientState *ncs, void *be,
     options.feature_bits = vdpa_feature_bits;
     options.get_acked_features = NULL;
     options.save_acked_features = NULL;
+    options.max_tx_queue_size = VIRTQUEUE_MAX_SIZE;
 
     net = vhost_net_init(&options);
     if (!net) {