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virtio-net: support XDP when not more queues 

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.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xuan Zhuo 2021-03-10 10:24:45 +08:00 committed by David S. Miller
parent 0bb3262c02
commit 97c2c69e19
1 changed files with 48 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
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 +484,41 @@ 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) ({ \
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 += smp_processor_id(); \
txq = netdev_get_tx_queue(v->dev, qp); \
__netif_tx_acquire(txq); \
} else { \
qp = smp_processor_id() % v->curr_queue_pairs; \
txq = netdev_get_tx_queue(v->dev, qp); \
__netif_tx_lock(txq, raw_smp_processor_id()); \
} \
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 +544,7 @@ 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 +592,13 @@ 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 +1491,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
xdp_do_flush();
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;
@ -2418,10 +2452,9 @@ 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",
netdev_warn(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);
return -ENOMEM;
xdp_qp = 0;
}
old_prog = rtnl_dereference(vi->rq[0].xdp_prog);
@ -2455,11 +2488,14 @@ 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++) {
@ -2527,7 +2563,7 @@ 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)