* [PATCH v5 net-next] virtio-net: support XDP when not more queues
@ 2021-03-01 3:22 Xuan Zhuo
2021-03-05 7:08 ` Jason Wang
0 siblings, 1 reply; 2+ messages in thread
From: Xuan Zhuo @ 2021-03-01 3:22 UTC (permalink / raw)
To: netdev
Cc: Michael S. Tsirkin, Jason Wang, David S. Miller, Jakub Kicinski,
Alexei Starovoitov, Daniel Borkmann, Jesper Dangaard Brouer,
John Fastabend, virtualization, bpf
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>
---
v5: change subject from 'support XDP_TX when not more queues'
v4: make sparse happy
suggested by Jakub Kicinski
v3: add warning when no more queues
suggested by Jesper Dangaard Brouer
drivers/net/virtio_net.c | 53 ++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 44 insertions(+), 9 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ba8e637..55f1dd1 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -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;
@@ -481,14 +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)
+static struct send_queue *virtnet_get_xdp_sq(struct virtnet_info *vi)
+ __acquires(lock)
{
+ struct netdev_queue *txq;
unsigned int qp;
- qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
+ if (vi->curr_queue_pairs > nr_cpu_ids) {
+ qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
+
+ /* tell sparse we took the lock, but don't really take it */
+ __acquire(lock);
+ } else {
+ qp = smp_processor_id() % vi->curr_queue_pairs;
+ txq = netdev_get_tx_queue(vi->dev, qp);
+ __netif_tx_lock(txq, raw_smp_processor_id());
+ }
+
return &vi->sq[qp];
}
+static void virtnet_put_xdp_sq(struct virtnet_info *vi, struct send_queue *sq)
+ __releases(lock)
+{
+ struct netdev_queue *txq;
+ unsigned int qp;
+
+ if (vi->curr_queue_pairs <= nr_cpu_ids) {
+ qp = sq - vi->sq;
+ txq = netdev_get_tx_queue(vi->dev, qp);
+ __netif_tx_unlock(txq);
+ } else {
+ /* make sparse happy */
+ __release(lock);
+ }
+}
+
static int virtnet_xdp_xmit(struct net_device *dev,
int n, struct xdp_frame **frames, u32 flags)
{
@@ -512,7 +543,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
if (!xdp_prog)
return -ENXIO;
- sq = virtnet_xdp_sq(vi);
+ sq = virtnet_get_xdp_sq(vi);
if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) {
ret = -EINVAL;
@@ -560,12 +591,13 @@ static int virtnet_xdp_xmit(struct net_device *dev,
sq->stats.kicks += kicks;
u64_stats_update_end(&sq->stats.syncp);
+ virtnet_put_xdp_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:
@@ -1457,12 +1489,13 @@ 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_get_xdp_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_put_xdp_sq(vi, sq);
}
return received;
@@ -2417,10 +2450,9 @@ 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);
@@ -2454,11 +2486,14 @@ 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++) {
@@ -2526,7 +2561,7 @@ 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)
--
1.8.3.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v5 net-next] virtio-net: support XDP when not more queues
2021-03-01 3:22 [PATCH v5 net-next] virtio-net: support XDP when not more queues Xuan Zhuo
@ 2021-03-05 7:08 ` Jason Wang
0 siblings, 0 replies; 2+ messages in thread
From: Jason Wang @ 2021-03-05 7:08 UTC (permalink / raw)
To: Xuan Zhuo, netdev
Cc: Michael S. Tsirkin, David S. Miller, Jakub Kicinski,
Alexei Starovoitov, Daniel Borkmann, Jesper Dangaard Brouer,
John Fastabend, virtualization, bpf
On 2021/3/1 11:22 上午, Xuan Zhuo wrote:
> 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>
> ---
> v5: change subject from 'support XDP_TX when not more queues'
>
> v4: make sparse happy
> suggested by Jakub Kicinski
>
> v3: add warning when no more queues
> suggested by Jesper Dangaard Brouer
>
> drivers/net/virtio_net.c | 53 ++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 44 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ba8e637..55f1dd1 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -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;
>
> @@ -481,14 +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)
> +static struct send_queue *virtnet_get_xdp_sq(struct virtnet_info *vi)
> + __acquires(lock)
> {
> + struct netdev_queue *txq;
> unsigned int qp;
>
> - qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
> + if (vi->curr_queue_pairs > nr_cpu_ids) {
> + qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
> +
> + /* tell sparse we took the lock, but don't really take it */
> + __acquire(lock);
The code can explain itself but you need to explain why we don't need to
hold tx lock here.
And it looks to me we should use __netif_tx_acquire()/__netif_tx_release()?
Btw, is it better to refactor the code then we can annote the code with
something like __acquire(txq->xmit_lock)?
Thanks
> + } else {
> + qp = smp_processor_id() % vi->curr_queue_pairs;
> + txq = netdev_get_tx_queue(vi->dev, qp);
> + __netif_tx_lock(txq, raw_smp_processor_id());
> + }
> +
> return &vi->sq[qp];
> }
>
> +static void virtnet_put_xdp_sq(struct virtnet_info *vi, struct send_queue *sq)
> + __releases(lock)
> +{
> + struct netdev_queue *txq;
> + unsigned int qp;
> +
> + if (vi->curr_queue_pairs <= nr_cpu_ids) {
> + qp = sq - vi->sq;
> + txq = netdev_get_tx_queue(vi->dev, qp);
> + __netif_tx_unlock(txq);
> + } else {
> + /* make sparse happy */
> + __release(lock);
> + }
> +}
> +
> static int virtnet_xdp_xmit(struct net_device *dev,
> int n, struct xdp_frame **frames, u32 flags)
> {
> @@ -512,7 +543,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
> if (!xdp_prog)
> return -ENXIO;
>
> - sq = virtnet_xdp_sq(vi);
> + sq = virtnet_get_xdp_sq(vi);
>
> if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK)) {
> ret = -EINVAL;
> @@ -560,12 +591,13 @@ static int virtnet_xdp_xmit(struct net_device *dev,
> sq->stats.kicks += kicks;
> u64_stats_update_end(&sq->stats.syncp);
>
> + virtnet_put_xdp_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:
> @@ -1457,12 +1489,13 @@ 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_get_xdp_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_put_xdp_sq(vi, sq);
> }
>
> return received;
> @@ -2417,10 +2450,9 @@ 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);
> @@ -2454,11 +2486,14 @@ 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++) {
> @@ -2526,7 +2561,7 @@ 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)
> --
> 1.8.3.1
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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