diff mbox series

[v5,net-next] virtio-net: support XDP when not more queues

Message ID 1614568959-107464-1-git-send-email-xuanzhuo@linux.alibaba.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series [v5,net-next] virtio-net: support XDP when not more queues | expand

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netdev/checkpatch warning WARNING: line length of 85 exceeds 80 columns
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netdev/stable success Stable not CCed

Commit Message

Xuan Zhuo March 1, 2021, 3:22 a.m. UTC 
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(-)

--
1.8.3.1

Comments

Jason Wang March 5, 2021, 7:08 a.m. UTC | #1 
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
>
diff mbox series

Patch

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)