[net-next,2/5] virtio-net: pack headroom into ctx for mergeable buffer

Message ID 1500295441-19339-3-git-send-email-jasowang@redhat.com
State Changes Requested
Delegated to: David Miller
Headers show

Commit Message

Jason Wang July 17, 2017, 12:43 p.m.
Pack headroom into ctx, then during XDP set, we could know the size of
headroom and copy if needed. This is required for avoiding reset on
XDP.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

Comments

Michael S. Tsirkin July 18, 2017, 6:59 p.m. | #1
On Mon, Jul 17, 2017 at 08:43:58PM +0800, Jason Wang wrote:
> Pack headroom into ctx, then during XDP set, we could know the size of
> headroom and copy if needed. This is required for avoiding reset on
> XDP.

Not really when XDP is set - it's when buffers are used.

virtio-net: pack headroom into ctx for mergeable buffers

Pack headroom into ctx - this way when we get a buffer we can figure out
the actual headroom that was allocated for the buffer. Will be helpful
to optimize switching between XDP and non-XDP modes which have different
headroom requirements.


> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++-----
>  1 file changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1f8c15c..8fae9a8 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -270,6 +270,23 @@ static void skb_xmit_done(struct virtqueue *vq)
>  		netif_wake_subqueue(vi->dev, vq2txq(vq));
>  }
>  
> +#define MRG_CTX_HEADER_SHIFT 22
> +static void *mergeable_len_to_ctx(unsigned int truesize,
> +				  unsigned int headroom)
> +{
> +	return (void *)(unsigned long)((headroom << MRG_CTX_HEADER_SHIFT) | truesize);
> +}
> +
> +static unsigned int mergeable_ctx_to_headroom(void *mrg_ctx)
> +{
> +	return (unsigned long)mrg_ctx >> MRG_CTX_HEADER_SHIFT;
> +}
> +
> +static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx)
> +{
> +	return (unsigned long)mrg_ctx & ((1 << MRG_CTX_HEADER_SHIFT) - 1);
> +}
> +
>  /* Called from bottom half context */
>  static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>  				   struct receive_queue *rq,
> @@ -639,13 +656,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  	}
>  	rcu_read_unlock();
>  
> -	if (unlikely(len > (unsigned long)ctx)) {
> +	truesize = mergeable_ctx_to_truesize(ctx);
> +	if (unlikely(len > truesize)) {
>  		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
>  			 dev->name, len, (unsigned long)ctx);
>  		dev->stats.rx_length_errors++;
>  		goto err_skb;
>  	}
> -	truesize = (unsigned long)ctx;
> +
>  	head_skb = page_to_skb(vi, rq, page, offset, len, truesize);
>  	curr_skb = head_skb;
>  
> @@ -665,13 +683,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  		}
>  
>  		page = virt_to_head_page(buf);
> -		if (unlikely(len > (unsigned long)ctx)) {
> +
> +		truesize = mergeable_ctx_to_truesize(ctx);
> +		if (unlikely(len > truesize)) {
>  			pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
>  				 dev->name, len, (unsigned long)ctx);
>  			dev->stats.rx_length_errors++;
>  			goto err_skb;
>  		}
> -		truesize = (unsigned long)ctx;
>  
>  		num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
>  		if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
> @@ -889,7 +908,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>  
>  	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
>  	buf += headroom; /* advance address leaving hole at front of pkt */
> -	ctx = (void *)(unsigned long)len;
> +	ctx = mergeable_len_to_ctx(len, headroom);
>  	get_page(alloc_frag->page);
>  	alloc_frag->offset += len + headroom;
>  	hole = alloc_frag->size - alloc_frag->offset;
> -- 
> 2.7.4
Jason Wang July 19, 2017, 2:29 a.m. | #2
On 2017年07月19日 02:59, Michael S. Tsirkin wrote:
> On Mon, Jul 17, 2017 at 08:43:58PM +0800, Jason Wang wrote:
>> Pack headroom into ctx, then during XDP set, we could know the size of
>> headroom and copy if needed. This is required for avoiding reset on
>> XDP.
> Not really when XDP is set - it's when buffers are used.

Of course :)

>
> virtio-net: pack headroom into ctx for mergeable buffers
>
> Pack headroom into ctx - this way when we get a buffer we can figure out
> the actual headroom that was allocated for the buffer. Will be helpful
> to optimize switching between XDP and non-XDP modes which have different
> headroom requirements.

Thanks, let me use this as the commit log.

>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++-----
>>   1 file changed, 24 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 1f8c15c..8fae9a8 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -270,6 +270,23 @@ static void skb_xmit_done(struct virtqueue *vq)
>>   		netif_wake_subqueue(vi->dev, vq2txq(vq));
>>   }
>>   
>> +#define MRG_CTX_HEADER_SHIFT 22
>> +static void *mergeable_len_to_ctx(unsigned int truesize,
>> +				  unsigned int headroom)
>> +{
>> +	return (void *)(unsigned long)((headroom << MRG_CTX_HEADER_SHIFT) | truesize);
>> +}
>> +
>> +static unsigned int mergeable_ctx_to_headroom(void *mrg_ctx)
>> +{
>> +	return (unsigned long)mrg_ctx >> MRG_CTX_HEADER_SHIFT;
>> +}
>> +
>> +static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx)
>> +{
>> +	return (unsigned long)mrg_ctx & ((1 << MRG_CTX_HEADER_SHIFT) - 1);
>> +}
>> +
>>   /* Called from bottom half context */
>>   static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>>   				   struct receive_queue *rq,
>> @@ -639,13 +656,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>>   	}
>>   	rcu_read_unlock();
>>   
>> -	if (unlikely(len > (unsigned long)ctx)) {
>> +	truesize = mergeable_ctx_to_truesize(ctx);
>> +	if (unlikely(len > truesize)) {
>>   		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
>>   			 dev->name, len, (unsigned long)ctx);
>>   		dev->stats.rx_length_errors++;
>>   		goto err_skb;
>>   	}
>> -	truesize = (unsigned long)ctx;
>> +
>>   	head_skb = page_to_skb(vi, rq, page, offset, len, truesize);
>>   	curr_skb = head_skb;
>>   
>> @@ -665,13 +683,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>>   		}
>>   
>>   		page = virt_to_head_page(buf);
>> -		if (unlikely(len > (unsigned long)ctx)) {
>> +
>> +		truesize = mergeable_ctx_to_truesize(ctx);
>> +		if (unlikely(len > truesize)) {
>>   			pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
>>   				 dev->name, len, (unsigned long)ctx);
>>   			dev->stats.rx_length_errors++;
>>   			goto err_skb;
>>   		}
>> -		truesize = (unsigned long)ctx;
>>   
>>   		num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
>>   		if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
>> @@ -889,7 +908,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>>   
>>   	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
>>   	buf += headroom; /* advance address leaving hole at front of pkt */
>> -	ctx = (void *)(unsigned long)len;
>> +	ctx = mergeable_len_to_ctx(len, headroom);
>>   	get_page(alloc_frag->page);
>>   	alloc_frag->offset += len + headroom;
>>   	hole = alloc_frag->size - alloc_frag->offset;
>> -- 
>> 2.7.4

Patch

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1f8c15c..8fae9a8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -270,6 +270,23 @@  static void skb_xmit_done(struct virtqueue *vq)
 		netif_wake_subqueue(vi->dev, vq2txq(vq));
 }
 
+#define MRG_CTX_HEADER_SHIFT 22
+static void *mergeable_len_to_ctx(unsigned int truesize,
+				  unsigned int headroom)
+{
+	return (void *)(unsigned long)((headroom << MRG_CTX_HEADER_SHIFT) | truesize);
+}
+
+static unsigned int mergeable_ctx_to_headroom(void *mrg_ctx)
+{
+	return (unsigned long)mrg_ctx >> MRG_CTX_HEADER_SHIFT;
+}
+
+static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx)
+{
+	return (unsigned long)mrg_ctx & ((1 << MRG_CTX_HEADER_SHIFT) - 1);
+}
+
 /* Called from bottom half context */
 static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 				   struct receive_queue *rq,
@@ -639,13 +656,14 @@  static struct sk_buff *receive_mergeable(struct net_device *dev,
 	}
 	rcu_read_unlock();
 
-	if (unlikely(len > (unsigned long)ctx)) {
+	truesize = mergeable_ctx_to_truesize(ctx);
+	if (unlikely(len > truesize)) {
 		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
 			 dev->name, len, (unsigned long)ctx);
 		dev->stats.rx_length_errors++;
 		goto err_skb;
 	}
-	truesize = (unsigned long)ctx;
+
 	head_skb = page_to_skb(vi, rq, page, offset, len, truesize);
 	curr_skb = head_skb;
 
@@ -665,13 +683,14 @@  static struct sk_buff *receive_mergeable(struct net_device *dev,
 		}
 
 		page = virt_to_head_page(buf);
-		if (unlikely(len > (unsigned long)ctx)) {
+
+		truesize = mergeable_ctx_to_truesize(ctx);
+		if (unlikely(len > truesize)) {
 			pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
 				 dev->name, len, (unsigned long)ctx);
 			dev->stats.rx_length_errors++;
 			goto err_skb;
 		}
-		truesize = (unsigned long)ctx;
 
 		num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
 		if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
@@ -889,7 +908,7 @@  static int add_recvbuf_mergeable(struct virtnet_info *vi,
 
 	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
 	buf += headroom; /* advance address leaving hole at front of pkt */
-	ctx = (void *)(unsigned long)len;
+	ctx = mergeable_len_to_ctx(len, headroom);
 	get_page(alloc_frag->page);
 	alloc_frag->offset += len + headroom;
 	hole = alloc_frag->size - alloc_frag->offset;