From: Mina Almasry

Sent: 06 November 2023 02:44

For device memory TCP, we expect the skb headers to be available in host memory for access, and we expect the skb frags to be in device memory and unaccessible to the host. We expect there to be no mixing and matching of device memory frags (unaccessible) with host memory frags (accessible) in the same skb.

Add a skb->devmem flag which indicates whether the frags in this skb are device memory frags or not.

...

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 1fae276c1353..8fb468ff8115 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -805,6 +805,8 @@ typedef unsigned char *sk_buff_data_t;

• @csum_level: indicates the number of consecutive checksums found in

• the packet minus one that have been verified as
  

• CHECKSUM_UNNECESSARY (max 3)
  

• • @devmem: indicates that all the fragments in this skb are backed by

• • device memory.
    

  • @dst_pending_confirm: need to confirm neighbour
  • @decrypted: Decrypted SKB
  • @slow_gro: state present at GRO time, slower prepare step required

@@ -991,7 +993,7 @@ struct sk_buff { #if IS_ENABLED(CONFIG_IP_SCTP) __u8 csum_not_inet:1; #endif

• __u8 devmem:1;

#if defined(CONFIG_NET_SCHED) || defined(CONFIG_NET_XGRESS) __u16 tc_index; /* traffic control index */ #endif @@ -1766,6 +1768,12 @@ static inline void skb_zcopy_downgrade_managed(struct sk_buff *skb) __skb_zcopy_downgrade_managed(skb); }

Doesn't that bloat struct sk_buff? I'm not sure there are any spare bits available. Although CONFIG_NET_SWITCHDEV and CONFIG_NET_SCHED seem to already add padding.

David

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