Re: [PATCH RESEND bpf-next 01/15] ice: make RX hash reading code more reusable

Alexander Lobakin
2023-05-19T16:48:38Z

From: Larysa Zaremba <larysa.zaremba@intel.com>
Date: Fri, 12 May 2023 17:25:53 +0200

> 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 <larysa.zaremba@intel.com>
> ---
> drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 38 +++++++++++++------
> 1 file changed, 27 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..fc67bbf600af 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
> @@ -63,28 +63,44 @@ static enum pkt_hash_types ice_ptype_to_htype(u16 ptype)
> }
>
> /**
> - * ice_rx_hash - set the hash value in the skb
> + * ice_copy_rx_hash_from_desc - copy hash value from descriptor to address
> + * @rx_desc: specific descriptor
> + * @dst: address to copy hash value to
> + *
> + * Returns true, if valid hash has been copied into the destination address.
> + */
> +static bool
> +ice_copy_rx_hash_from_desc(union ice_32b_rx_flex_desc *rx_desc, u32 *dst)

@rx_desc can be const.

I'm also unsure about the naming. Why not name this one ice_rx_hash()
and the one which sets it in skb ice_rx_hash_skb()?

> +{
> + struct ice_32b_rx_flex_desc_nic *nic_mdid;

Also const. I thought you'll pick most of my optimizations from the
related commit :D

> +
> + if (rx_desc->wb.rxdid != ICE_RXDID_FLEX_NIC)
> + return false;
> +
> + nic_mdid = (struct ice_32b_rx_flex_desc_nic *)rx_desc;
> + *dst = le32_to_cpu(nic_mdid->rss_hash);
> + return true;

You can just return the hash. `hash == 0` means there's no hash, so it
basically means `false`, while non-zero is `true`.

> +}
> +
> +/**
> + * 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(struct ice_rx_ring *rx_ring,
> + 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));
> + if (ice_copy_rx_hash_from_desc(rx_desc, &hash))

likely()? I wouldn't care about zero-hashed frames, their perf is not
critical anyway.

> + skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));
> }
>
> /**
> @@ -186,7 +202,7 @@ 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);

Thanks,
Olek