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virtio-net: support XDP when not more queues 

97c2c69e19 support XDP when not more queues
9ce4e3d6d8 use netdev_warn_once to output warn when without enough queues
3dcc1edcbb reduce raw_smp_processor_id() calling in virtnet_xdp_get_sq

[97c2c69e19 desc]
The number of queues implemented by many virtio backends is limited,
especially some machines have a large number of CPUs. In this case, it
is often impossible to allocate a separate queue for
XDP_TX/XDP_REDIRECT, then xdp cannot be loaded to work, even xdp does
not use the XDP_TX/XDP_REDIRECT.

This patch allows XDP_TX/XDP_REDIRECT to run by reuse the existing SQ
with __netif_tx_lock() hold when there are not enough queues.

[9ce4e3d6d8 disc]
This warning is output when virtnet does not have enough queues, but it
only needs to be printed once to inform the user of this situation. It
is not necessary to print it every time. If the user loads xdp
frequently, this log appears too much.

[3dcc1edcbb desc]
smp_processor_id()/raw* will be called once each when not
more queues in virtnet_xdp_get_sq() which is called in
non-preemptible context, so it's safe to call the function
smp_processor_id() once.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
This commit is contained in:
mengensun 2021-12-15 16:57:13 +08:00 committed by kaixuxiakx
parent e065537049
commit 1d0a3bfff9
1 changed files with 50 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
drivers/net/virtio_net.c
View File

@ -195,6 +195,9 @@ struct virtnet_info {
/* # of XDP queue pairs currently used by the driver */
u16 xdp_queue_pairs;
/* xdp_queue_pairs may be 0, when xdp is already loaded. So add this. */
bool xdp_enabled;
/* I like... big packets and I cannot lie! */
bool big_packets;
@ -481,12 +484,42 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
return 0;
}
static struct send_queue *virtnet_xdp_sq(struct virtnet_info *vi)
{
unsigned int qp;
/* when vi->curr_queue_pairs > nr_cpu_ids, the txq/sq is only used for xdp tx on
* the current cpu, so it does not need to be locked.
*
* Here we use marco instead of inline functions because we have to deal with
* three issues at the same time: 1. the choice of sq. 2. judge and execute the
* lock/unlock of txq 3. make sparse happy. It is difficult for two inline
* functions to perfectly solve these three problems at the same time.
*/
#define virtnet_xdp_get_sq(vi) ({ \
int cpu = smp_processor_id(); \
struct netdev_queue *txq; \
typeof(vi) v = (vi); \
unsigned int qp; \
\
if (v->curr_queue_pairs > nr_cpu_ids) { \
qp = v->curr_queue_pairs - v->xdp_queue_pairs; \
qp += cpu; \
txq = netdev_get_tx_queue(v->dev, qp); \
__netif_tx_acquire(txq); \
} else { \
qp = cpu % v->curr_queue_pairs; \
txq = netdev_get_tx_queue(v->dev, qp); \
__netif_tx_lock(txq, cpu); \
} \
v->sq + qp; \
})
qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
return &vi->sq[qp];
#define virtnet_xdp_put_sq(vi, q) { \
struct netdev_queue *txq; \
typeof(vi) v = (vi); \
\
txq = netdev_get_tx_queue(v->dev, (q) - v->sq); \
if (v->curr_queue_pairs > nr_cpu_ids) \
__netif_tx_release(txq); \
else \
__netif_tx_unlock(txq); \
}
static int virtnet_xdp_xmit(struct net_device *dev,
@ -512,7 +545,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
if (!xdp_prog)
return -ENXIO;
sq = virtnet_xdp_sq(vi);
sq = virtnet_xdp_get_sq(vi);
if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) {
ret = -EINVAL;
@ -560,12 +593,13 @@ out:
sq->stats.kicks += kicks;
u64_stats_update_end(&sq->stats.syncp);
virtnet_xdp_put_sq(vi, sq);
return ret;
}
static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
{
return vi->xdp_queue_pairs ? VIRTIO_XDP_HEADROOM : 0;
return vi->xdp_enabled ? VIRTIO_XDP_HEADROOM : 0;
}
/* We copy the packet for XDP in the following cases:
@ -1458,12 +1492,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
xdp_do_flush_map();
if (xdp_xmit & VIRTIO_XDP_TX) {
sq = virtnet_xdp_sq(vi);
sq = virtnet_xdp_get_sq(vi);
if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) {
u64_stats_update_begin(&sq->stats.syncp);
sq->stats.kicks++;
u64_stats_update_end(&sq->stats.syncp);
}
virtnet_xdp_put_sq(vi, sq);
}
return received;
@ -2486,10 +2521,9 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
/* XDP requires extra queues for XDP_TX */
if (curr_qp + xdp_qp > vi->max_queue_pairs) {
NL_SET_ERR_MSG_MOD(extack, "Too few free TX rings available");
netdev_warn(dev, "request %i queues but max is %i\n",
curr_qp + xdp_qp, vi->max_queue_pairs);
return -ENOMEM;
netdev_warn_once(dev, "XDP request %i queues but max is %i. XDP_TX and XDP_REDIRECT will operate in a slower locked tx mode.\n",
curr_qp + xdp_qp, vi->max_queue_pairs);
xdp_qp = 0;
}
old_prog = rtnl_dereference(vi->rq[0].xdp_prog);
@ -2523,11 +2557,14 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
vi->xdp_queue_pairs = xdp_qp;
if (prog) {
vi->xdp_enabled = true;
for (i = 0; i < vi->max_queue_pairs; i++) {
rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
if (i == 0 && !old_prog)
virtnet_clear_guest_offloads(vi);
}
} else {
vi->xdp_enabled = false;
}
for (i = 0; i < vi->max_queue_pairs; i++) {
@ -2612,7 +2649,7 @@ static int virtnet_set_features(struct net_device *dev,
int err;
if ((dev->features ^ features) & NETIF_F_LRO) {
if (vi->xdp_queue_pairs)
if (vi->xdp_enabled)
return -EBUSY;
if (features & NETIF_F_LRO)