summaryrefslogtreecommitdiffstats
path: root/drivers/net/virtio_net.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/net/virtio_net.c')
-rw-r--r--drivers/net/virtio_net.c350
1 files changed, 285 insertions, 65 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1caf21fd50..ec14bf2a9a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -19,6 +19,7 @@
#include <linux/average.h>
#include <linux/filter.h>
#include <linux/kernel.h>
+#include <linux/dim.h>
#include <net/route.h>
#include <net/xdp.h>
#include <net/net_failover.h>
@@ -172,6 +173,17 @@ struct receive_queue {
struct virtnet_rq_stats stats;
+ /* The number of rx notifications */
+ u16 calls;
+
+ /* Is dynamic interrupt moderation enabled? */
+ bool dim_enabled;
+
+ /* Dynamic Interrupt Moderation */
+ struct dim dim;
+
+ u32 packets_in_napi;
+
struct virtnet_interrupt_coalesce intr_coal;
/* Chain pages by the private ptr. */
@@ -305,6 +317,9 @@ struct virtnet_info {
u8 duplex;
u32 speed;
+ /* Is rx dynamic interrupt moderation enabled? */
+ bool rx_dim_enabled;
+
/* Interrupt coalescing settings */
struct virtnet_interrupt_coalesce intr_coal_tx;
struct virtnet_interrupt_coalesce intr_coal_rx;
@@ -441,7 +456,7 @@ static void virtqueue_napi_schedule(struct napi_struct *napi,
}
}
-static void virtqueue_napi_complete(struct napi_struct *napi,
+static bool virtqueue_napi_complete(struct napi_struct *napi,
struct virtqueue *vq, int processed)
{
int opaque;
@@ -450,9 +465,13 @@ static void virtqueue_napi_complete(struct napi_struct *napi,
if (napi_complete_done(napi, processed)) {
if (unlikely(virtqueue_poll(vq, opaque)))
virtqueue_napi_schedule(napi, vq);
+ else
+ return true;
} else {
virtqueue_disable_cb(vq);
}
+
+ return false;
}
static void skb_xmit_done(struct virtqueue *vq)
@@ -2010,6 +2029,7 @@ static void skb_recv_done(struct virtqueue *rvq)
struct virtnet_info *vi = rvq->vdev->priv;
struct receive_queue *rq = &vi->rq[vq2rxq(rvq)];
+ rq->calls++;
virtqueue_napi_schedule(&rq->napi, rvq);
}
@@ -2150,6 +2170,24 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
}
}
+static void virtnet_rx_dim_update(struct virtnet_info *vi, struct receive_queue *rq)
+{
+ struct dim_sample cur_sample = {};
+
+ if (!rq->packets_in_napi)
+ return;
+
+ u64_stats_update_begin(&rq->stats.syncp);
+ dim_update_sample(rq->calls,
+ u64_stats_read(&rq->stats.packets),
+ u64_stats_read(&rq->stats.bytes),
+ &cur_sample);
+ u64_stats_update_end(&rq->stats.syncp);
+
+ net_dim(&rq->dim, cur_sample);
+ rq->packets_in_napi = 0;
+}
+
static int virtnet_poll(struct napi_struct *napi, int budget)
{
struct receive_queue *rq =
@@ -2158,17 +2196,22 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
struct send_queue *sq;
unsigned int received;
unsigned int xdp_xmit = 0;
+ bool napi_complete;
virtnet_poll_cleantx(rq);
received = virtnet_receive(rq, budget, &xdp_xmit);
+ rq->packets_in_napi += received;
if (xdp_xmit & VIRTIO_XDP_REDIR)
xdp_do_flush();
/* Out of packets? */
- if (received < budget)
- virtqueue_napi_complete(napi, rq->vq, received);
+ if (received < budget) {
+ napi_complete = virtqueue_napi_complete(napi, rq->vq, received);
+ if (napi_complete && rq->dim_enabled)
+ virtnet_rx_dim_update(vi, rq);
+ }
if (xdp_xmit & VIRTIO_XDP_TX) {
sq = virtnet_xdp_get_sq(vi);
@@ -2239,8 +2282,11 @@ err_enable_qp:
disable_delayed_refill(vi);
cancel_delayed_work_sync(&vi->refill);
- for (i--; i >= 0; i--)
+ for (i--; i >= 0; i--) {
virtnet_disable_queue_pair(vi, i);
+ cancel_work_sync(&vi->rq[i].dim.work);
+ }
+
return err;
}
@@ -2402,8 +2448,10 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
qindex = rq - vi->rq;
- if (running)
+ if (running) {
napi_disable(&rq->napi);
+ cancel_work_sync(&rq->dim.work);
+ }
err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_unmap_free_buf);
if (err)
@@ -2650,8 +2698,10 @@ static int virtnet_close(struct net_device *dev)
/* Make sure refill_work doesn't re-enable napi! */
cancel_delayed_work_sync(&vi->refill);
- for (i = 0; i < vi->max_queue_pairs; i++)
+ for (i = 0; i < vi->max_queue_pairs; i++) {
virtnet_disable_queue_pair(vi, i);
+ cancel_work_sync(&vi->rq[i].dim.work);
+ }
return 0;
}
@@ -2858,6 +2908,58 @@ static void virtnet_cpu_notif_remove(struct virtnet_info *vi)
&vi->node_dead);
}
+static int virtnet_send_ctrl_coal_vq_cmd(struct virtnet_info *vi,
+ u16 vqn, u32 max_usecs, u32 max_packets)
+{
+ struct scatterlist sgs;
+
+ vi->ctrl->coal_vq.vqn = cpu_to_le16(vqn);
+ vi->ctrl->coal_vq.coal.max_usecs = cpu_to_le32(max_usecs);
+ vi->ctrl->coal_vq.coal.max_packets = cpu_to_le32(max_packets);
+ sg_init_one(&sgs, &vi->ctrl->coal_vq, sizeof(vi->ctrl->coal_vq));
+
+ if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
+ VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET,
+ &sgs))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int virtnet_send_rx_ctrl_coal_vq_cmd(struct virtnet_info *vi,
+ u16 queue, u32 max_usecs,
+ u32 max_packets)
+{
+ int err;
+
+ err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(queue),
+ max_usecs, max_packets);
+ if (err)
+ return err;
+
+ vi->rq[queue].intr_coal.max_usecs = max_usecs;
+ vi->rq[queue].intr_coal.max_packets = max_packets;
+
+ return 0;
+}
+
+static int virtnet_send_tx_ctrl_coal_vq_cmd(struct virtnet_info *vi,
+ u16 queue, u32 max_usecs,
+ u32 max_packets)
+{
+ int err;
+
+ err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(queue),
+ max_usecs, max_packets);
+ if (err)
+ return err;
+
+ vi->sq[queue].intr_coal.max_usecs = max_usecs;
+ vi->sq[queue].intr_coal.max_packets = max_packets;
+
+ return 0;
+}
+
static void virtnet_get_ringparam(struct net_device *dev,
struct ethtool_ringparam *ring,
struct kernel_ethtool_ringparam *kernel_ring,
@@ -2871,9 +2973,6 @@ static void virtnet_get_ringparam(struct net_device *dev,
ring->tx_pending = virtqueue_get_vring_size(vi->sq[0].vq);
}
-static int virtnet_send_ctrl_coal_vq_cmd(struct virtnet_info *vi,
- u16 vqn, u32 max_usecs, u32 max_packets);
-
static int virtnet_set_ringparam(struct net_device *dev,
struct ethtool_ringparam *ring,
struct kernel_ethtool_ringparam *kernel_ring,
@@ -2915,14 +3014,11 @@ static int virtnet_set_ringparam(struct net_device *dev,
* through the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or, if the driver
* did not set any TX coalescing parameters, to 0.
*/
- err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(i),
- vi->intr_coal_tx.max_usecs,
- vi->intr_coal_tx.max_packets);
+ err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i,
+ vi->intr_coal_tx.max_usecs,
+ vi->intr_coal_tx.max_packets);
if (err)
return err;
-
- vi->sq[i].intr_coal.max_usecs = vi->intr_coal_tx.max_usecs;
- vi->sq[i].intr_coal.max_packets = vi->intr_coal_tx.max_packets;
}
if (ring->rx_pending != rx_pending) {
@@ -2931,14 +3027,11 @@ static int virtnet_set_ringparam(struct net_device *dev,
return err;
/* The reason is same as the transmit virtqueue reset */
- err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(i),
- vi->intr_coal_rx.max_usecs,
- vi->intr_coal_rx.max_packets);
+ err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, i,
+ vi->intr_coal_rx.max_usecs,
+ vi->intr_coal_rx.max_packets);
if (err)
return err;
-
- vi->rq[i].intr_coal.max_usecs = vi->intr_coal_rx.max_usecs;
- vi->rq[i].intr_coal.max_packets = vi->intr_coal_rx.max_packets;
}
}
@@ -3275,10 +3368,10 @@ static int virtnet_get_link_ksettings(struct net_device *dev,
return 0;
}
-static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
- struct ethtool_coalesce *ec)
+static int virtnet_send_tx_notf_coal_cmds(struct virtnet_info *vi,
+ struct ethtool_coalesce *ec)
{
- struct scatterlist sgs_tx, sgs_rx;
+ struct scatterlist sgs_tx;
int i;
vi->ctrl->coal_tx.tx_usecs = cpu_to_le32(ec->tx_coalesce_usecs);
@@ -3290,7 +3383,6 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
&sgs_tx))
return -EINVAL;
- /* Save parameters */
vi->intr_coal_tx.max_usecs = ec->tx_coalesce_usecs;
vi->intr_coal_tx.max_packets = ec->tx_max_coalesced_frames;
for (i = 0; i < vi->max_queue_pairs; i++) {
@@ -3298,6 +3390,40 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
vi->sq[i].intr_coal.max_packets = ec->tx_max_coalesced_frames;
}
+ return 0;
+}
+
+static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi,
+ struct ethtool_coalesce *ec)
+{
+ bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
+ struct scatterlist sgs_rx;
+ int i;
+
+ if (rx_ctrl_dim_on && !virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
+ return -EOPNOTSUPP;
+
+ if (rx_ctrl_dim_on && (ec->rx_coalesce_usecs != vi->intr_coal_rx.max_usecs ||
+ ec->rx_max_coalesced_frames != vi->intr_coal_rx.max_packets))
+ return -EINVAL;
+
+ if (rx_ctrl_dim_on && !vi->rx_dim_enabled) {
+ vi->rx_dim_enabled = true;
+ for (i = 0; i < vi->max_queue_pairs; i++)
+ vi->rq[i].dim_enabled = true;
+ return 0;
+ }
+
+ if (!rx_ctrl_dim_on && vi->rx_dim_enabled) {
+ vi->rx_dim_enabled = false;
+ for (i = 0; i < vi->max_queue_pairs; i++)
+ vi->rq[i].dim_enabled = false;
+ }
+
+ /* Since the per-queue coalescing params can be set,
+ * we need apply the global new params even if they
+ * are not updated.
+ */
vi->ctrl->coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
vi->ctrl->coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
sg_init_one(&sgs_rx, &vi->ctrl->coal_rx, sizeof(vi->ctrl->coal_rx));
@@ -3307,7 +3433,6 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
&sgs_rx))
return -EINVAL;
- /* Save parameters */
vi->intr_coal_rx.max_usecs = ec->rx_coalesce_usecs;
vi->intr_coal_rx.max_packets = ec->rx_max_coalesced_frames;
for (i = 0; i < vi->max_queue_pairs; i++) {
@@ -3318,21 +3443,55 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
return 0;
}
-static int virtnet_send_ctrl_coal_vq_cmd(struct virtnet_info *vi,
- u16 vqn, u32 max_usecs, u32 max_packets)
+static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
+ struct ethtool_coalesce *ec)
{
- struct scatterlist sgs;
+ int err;
- vi->ctrl->coal_vq.vqn = cpu_to_le16(vqn);
- vi->ctrl->coal_vq.coal.max_usecs = cpu_to_le32(max_usecs);
- vi->ctrl->coal_vq.coal.max_packets = cpu_to_le32(max_packets);
- sg_init_one(&sgs, &vi->ctrl->coal_vq, sizeof(vi->ctrl->coal_vq));
+ err = virtnet_send_tx_notf_coal_cmds(vi, ec);
+ if (err)
+ return err;
- if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
- VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET,
- &sgs))
+ err = virtnet_send_rx_notf_coal_cmds(vi, ec);
+ if (err)
+ return err;
+
+ return 0;
+}
+
+static int virtnet_send_rx_notf_coal_vq_cmds(struct virtnet_info *vi,
+ struct ethtool_coalesce *ec,
+ u16 queue)
+{
+ bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
+ bool cur_rx_dim = vi->rq[queue].dim_enabled;
+ u32 max_usecs, max_packets;
+ int err;
+
+ max_usecs = vi->rq[queue].intr_coal.max_usecs;
+ max_packets = vi->rq[queue].intr_coal.max_packets;
+
+ if (rx_ctrl_dim_on && (ec->rx_coalesce_usecs != max_usecs ||
+ ec->rx_max_coalesced_frames != max_packets))
return -EINVAL;
+ if (rx_ctrl_dim_on && !cur_rx_dim) {
+ vi->rq[queue].dim_enabled = true;
+ return 0;
+ }
+
+ if (!rx_ctrl_dim_on && cur_rx_dim)
+ vi->rq[queue].dim_enabled = false;
+
+ /* If no params are updated, userspace ethtool will
+ * reject the modification.
+ */
+ err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, queue,
+ ec->rx_coalesce_usecs,
+ ec->rx_max_coalesced_frames);
+ if (err)
+ return err;
+
return 0;
}
@@ -3342,27 +3501,62 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
{
int err;
- err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(queue),
- ec->rx_coalesce_usecs,
- ec->rx_max_coalesced_frames);
+ err = virtnet_send_rx_notf_coal_vq_cmds(vi, ec, queue);
if (err)
return err;
- vi->rq[queue].intr_coal.max_usecs = ec->rx_coalesce_usecs;
- vi->rq[queue].intr_coal.max_packets = ec->rx_max_coalesced_frames;
-
- err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(queue),
- ec->tx_coalesce_usecs,
- ec->tx_max_coalesced_frames);
+ err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, queue,
+ ec->tx_coalesce_usecs,
+ ec->tx_max_coalesced_frames);
if (err)
return err;
- vi->sq[queue].intr_coal.max_usecs = ec->tx_coalesce_usecs;
- vi->sq[queue].intr_coal.max_packets = ec->tx_max_coalesced_frames;
-
return 0;
}
+static void virtnet_rx_dim_work(struct work_struct *work)
+{
+ struct dim *dim = container_of(work, struct dim, work);
+ struct receive_queue *rq = container_of(dim,
+ struct receive_queue, dim);
+ struct virtnet_info *vi = rq->vq->vdev->priv;
+ struct net_device *dev = vi->dev;
+ struct dim_cq_moder update_moder;
+ int i, qnum, err;
+
+ if (!rtnl_trylock())
+ return;
+
+ /* Each rxq's work is queued by "net_dim()->schedule_work()"
+ * in response to NAPI traffic changes. Note that dim->profile_ix
+ * for each rxq is updated prior to the queuing action.
+ * So we only need to traverse and update profiles for all rxqs
+ * in the work which is holding rtnl_lock.
+ */
+ for (i = 0; i < vi->curr_queue_pairs; i++) {
+ rq = &vi->rq[i];
+ dim = &rq->dim;
+ qnum = rq - vi->rq;
+
+ if (!rq->dim_enabled)
+ continue;
+
+ update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
+ if (update_moder.usec != rq->intr_coal.max_usecs ||
+ update_moder.pkts != rq->intr_coal.max_packets) {
+ err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, qnum,
+ update_moder.usec,
+ update_moder.pkts);
+ if (err)
+ pr_debug("%s: Failed to send dim parameters on rxq%d\n",
+ dev->name, qnum);
+ dim->state = DIM_START_MEASURE;
+ }
+ }
+
+ rtnl_unlock();
+}
+
static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
{
/* usecs coalescing is supported only if VIRTIO_NET_F_NOTF_COAL
@@ -3444,6 +3638,7 @@ static int virtnet_get_coalesce(struct net_device *dev,
ec->tx_coalesce_usecs = vi->intr_coal_tx.max_usecs;
ec->tx_max_coalesced_frames = vi->intr_coal_tx.max_packets;
ec->rx_max_coalesced_frames = vi->intr_coal_rx.max_packets;
+ ec->use_adaptive_rx_coalesce = vi->rx_dim_enabled;
} else {
ec->rx_max_coalesced_frames = 1;
@@ -3501,6 +3696,7 @@ static int virtnet_get_per_queue_coalesce(struct net_device *dev,
ec->tx_coalesce_usecs = vi->sq[queue].intr_coal.max_usecs;
ec->tx_max_coalesced_frames = vi->sq[queue].intr_coal.max_packets;
ec->rx_max_coalesced_frames = vi->rq[queue].intr_coal.max_packets;
+ ec->use_adaptive_rx_coalesce = vi->rq[queue].dim_enabled;
} else {
ec->rx_max_coalesced_frames = 1;
@@ -3548,41 +3744,60 @@ static u32 virtnet_get_rxfh_indir_size(struct net_device *dev)
return ((struct virtnet_info *)netdev_priv(dev))->rss_indir_table_size;
}
-static int virtnet_get_rxfh(struct net_device *dev, u32 *indir, u8 *key, u8 *hfunc)
+static int virtnet_get_rxfh(struct net_device *dev,
+ struct ethtool_rxfh_param *rxfh)
{
struct virtnet_info *vi = netdev_priv(dev);
int i;
- if (indir) {
+ if (rxfh->indir) {
for (i = 0; i < vi->rss_indir_table_size; ++i)
- indir[i] = vi->ctrl->rss.indirection_table[i];
+ rxfh->indir[i] = vi->ctrl->rss.indirection_table[i];
}
- if (key)
- memcpy(key, vi->ctrl->rss.key, vi->rss_key_size);
+ if (rxfh->key)
+ memcpy(rxfh->key, vi->ctrl->rss.key, vi->rss_key_size);
- if (hfunc)
- *hfunc = ETH_RSS_HASH_TOP;
+ rxfh->hfunc = ETH_RSS_HASH_TOP;
return 0;
}
-static int virtnet_set_rxfh(struct net_device *dev, const u32 *indir, const u8 *key, const u8 hfunc)
+static int virtnet_set_rxfh(struct net_device *dev,
+ struct ethtool_rxfh_param *rxfh,
+ struct netlink_ext_ack *extack)
{
struct virtnet_info *vi = netdev_priv(dev);
+ bool update = false;
int i;
- if (hfunc != ETH_RSS_HASH_NO_CHANGE && hfunc != ETH_RSS_HASH_TOP)
+ if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
+ rxfh->hfunc != ETH_RSS_HASH_TOP)
return -EOPNOTSUPP;
- if (indir) {
+ if (rxfh->indir) {
+ if (!vi->has_rss)
+ return -EOPNOTSUPP;
+
for (i = 0; i < vi->rss_indir_table_size; ++i)
- vi->ctrl->rss.indirection_table[i] = indir[i];
+ vi->ctrl->rss.indirection_table[i] = rxfh->indir[i];
+ update = true;
}
- if (key)
- memcpy(vi->ctrl->rss.key, key, vi->rss_key_size);
- virtnet_commit_rss_command(vi);
+ if (rxfh->key) {
+ /* If either _F_HASH_REPORT or _F_RSS are negotiated, the
+ * device provides hash calculation capabilities, that is,
+ * hash_key is configured.
+ */
+ if (!vi->has_rss && !vi->has_rss_hash_report)
+ return -EOPNOTSUPP;
+
+ memcpy(vi->ctrl->rss.key, rxfh->key, vi->rss_key_size);
+ update = true;
+ }
+
+ if (update)
+ virtnet_commit_rss_command(vi);
return 0;
}
@@ -3626,7 +3841,7 @@ static int virtnet_set_rxnfc(struct net_device *dev, struct ethtool_rxnfc *info)
static const struct ethtool_ops virtnet_ethtool_ops = {
.supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES |
- ETHTOOL_COALESCE_USECS,
+ ETHTOOL_COALESCE_USECS | ETHTOOL_COALESCE_USE_ADAPTIVE_RX,
.get_drvinfo = virtnet_get_drvinfo,
.get_link = ethtool_op_get_link,
.get_ringparam = virtnet_get_ringparam,
@@ -4204,6 +4419,9 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
virtnet_poll_tx,
napi_tx ? napi_weight : 0);
+ INIT_WORK(&vi->rq[i].dim.work, virtnet_rx_dim_work);
+ vi->rq[i].dim.mode = DIM_CQ_PERIOD_MODE_START_FROM_EQE;
+
sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
ewma_pkt_len_init(&vi->rq[i].mrg_avg_pkt_len);
sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
@@ -4484,13 +4702,15 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
vi->has_rss_hash_report = true;
- if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) {
vi->has_rss = true;
- if (vi->has_rss || vi->has_rss_hash_report) {
vi->rss_indir_table_size =
virtio_cread16(vdev, offsetof(struct virtio_net_config,
rss_max_indirection_table_length));
+ }
+
+ if (vi->has_rss || vi->has_rss_hash_report) {
vi->rss_key_size =
virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size));