Subject: Re: [xdp-hints] [RFC bpf-next 01/23] ice: make RX hash reading code more reusable

From: Maciej Fijalkowski <[email-masked]>
Date: Mon, 4 Sep 2023 16:37:45 +0200

On Thu, Aug 24, 2023 at 09:26:40PM +0200, Larysa Zaremba wrote:
> Previously, we only needed RX hash in skb path,
> hence all related code was written with skb in mind.
> But with the addition of XDP hints via kfuncs to the ice driver,
> the same logic will be needed in .xmo_() callbacks.
> 
> Separate generic process of reading RX hash from a descriptor
> into a separate function.
> 
> Signed-off-by: Larysa Zaremba <[email-masked]>
> ---
>  drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 37 +++++++++++++------
>  1 file changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> index c8322fb6f2b3..8f7f6d78f7bf 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> @@ -63,28 +63,43 @@ static enum pkt_hash_types ice_ptype_to_htype(u16 ptype)
>  }
>  
>  /**
> - * ice_rx_hash - set the hash value in the skb
> + * ice_get_rx_hash - get RX hash value from descriptor
> + * @rx_desc: specific descriptor
> + *
> + * Returns hash, if present, 0 otherwise.
> + */
> +static u32
> +ice_get_rx_hash(const union ice_32b_rx_flex_desc *rx_desc)
> +{
> +	const struct ice_32b_rx_flex_desc_nic *nic_mdid;
> +
> +	if (rx_desc->wb.rxdid != ICE_RXDID_FLEX_NIC)
> +		return 0;
> +
> +	nic_mdid = (struct ice_32b_rx_flex_desc_nic *)rx_desc;
> +	return le32_to_cpu(nic_mdid->rss_hash);
> +}
> +
> +/**
> + * ice_rx_hash_to_skb - set the hash value in the skb
>   * @rx_ring: descriptor ring
>   * @rx_desc: specific descriptor
>   * @skb: pointer to current skb
>   * @rx_ptype: the ptype value from the descriptor
>   */
>  static void
> -ice_rx_hash(struct ice_rx_ring *rx_ring, union ice_32b_rx_flex_desc *rx_desc,
> -	    struct sk_buff *skb, u16 rx_ptype)
> +ice_rx_hash_to_skb(const struct ice_rx_ring *rx_ring,

nit: maybe ice_rx_skb_hash, but i have not seen xdp side yet.

other idea would be to turn ice_get_rx_hash to __ice_rx_hash and keep the
ice_rx_hash name as-is. Usual way of naming internal funcs.

Take it or leave it:)

> +		   const union ice_32b_rx_flex_desc *rx_desc,
> +		   struct sk_buff *skb, u16 rx_ptype)
>  {
> -	struct ice_32b_rx_flex_desc_nic *nic_mdid;
>  	u32 hash;
>  
>  	if (!(rx_ring->netdev->features & NETIF_F_RXHASH))
>  		return;
>  
> -	if (rx_desc->wb.rxdid != ICE_RXDID_FLEX_NIC)
> -		return;
> -
> -	nic_mdid = (struct ice_32b_rx_flex_desc_nic *)rx_desc;
> -	hash = le32_to_cpu(nic_mdid->rss_hash);
> -	skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));
> +	hash = ice_get_rx_hash(rx_desc);
> +	if (likely(hash))
> +		skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));

Looks like a behavior change as you wouldn't be setting l4_hash and
sw_hash from skb in case !hash ? When can we get hash == 0 ?

>  }
>  
>  /**
> @@ -186,7 +201,7 @@ ice_process_skb_fields(struct ice_rx_ring *rx_ring,
>  		       union ice_32b_rx_flex_desc *rx_desc,
>  		       struct sk_buff *skb, u16 ptype)
>  {
> -	ice_rx_hash(rx_ring, rx_desc, skb, ptype);
> +	ice_rx_hash_to_skb(rx_ring, rx_desc, skb, ptype);
>  
>  	/* modifies the skb - consumes the enet header */
>  	skb->protocol = eth_type_trans(skb, rx_ring->netdev);
> -- 
> 2.41.0
>