netdev - Re: [PATCH net-next v3 0/6] tsnep: XDP socket zero-copy support

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Date:   Thu, 20 Apr 2023 22:19:01 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Gerhard Engleder <gerhard@...leder-embedded.com>
CC:     <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <davem@...emloft.net>, <kuba@...nel.org>, <edumazet@...gle.com>,
        <pabeni@...hat.com>, <bjorn@...nel.org>,
        <magnus.karlsson@...el.com>, <jonathan.lemon@...il.com>
Subject: Re: [PATCH net-next v3 0/6] tsnep: XDP socket zero-copy support

On Tue, Apr 18, 2023 at 09:04:53PM +0200, Gerhard Engleder wrote:
> Implement XDP socket zero-copy support for tsnep driver. I tried to
> follow existing drivers like igc as far as possible. But one main
> difference is that tsnep does not need any reconfiguration for XDP BPF
> program setup. So I decided to keep this behavior no matter if a XSK
> pool is used or not. As a result, tsnep starts using the XSK pool even
> if no XDP BPF program is available.
> 
> Another difference is that I tried to prevent potentially failing
> allocations during XSK pool setup. E.g. both memory models for page pool
> and XSK pool are registered all the time. Thus, XSK pool setup cannot
> end up with not working queues.
> 
> Some prework is done to reduce the last two XSK commits to actual XSK
> changes.

I had minor comments on two last patches, besides:
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>

> 
> v3:
> - use __netif_tx_lock_bh() (Paolo Abeni)
> - comment that rx->page_buffer is always zero terminated (Paolo Abeni)
> 
> v2:
> - eliminate modulo op in TX/RX path (Maciej Fijalkowski)
> - eliminate retval variable in tsnep_rx_alloc_zc() (Maciej Fijalkowski)
> - scope variable entry within loop (Maciej Fijalkowski)
> - use DMA_ATTR_SKIP_CPU_SYNC directly (Maciej Fijalkowski)
> - union for page/xdp in tsnep_rx_entry (Maciej Fijalkowski)
> - provide performance numbers (Maciej Fijalkowski)
> - use xsk_buff_alloc_batch() (Maciej Fijalkowski)
> - use xsk_tx_peek_release_desc_batch() (Maciej Fijalkowski)
> - don't call tsnep_rx_reopen() if netdev is down
> - init adapter pointer of queue only once
> 
> Gerhard Engleder (6):
>   tsnep: Replace modulo operation with mask
>   tsnep: Rework TX/RX queue initialization
>   tsnep: Add functions for queue enable/disable
>   tsnep: Move skb receive action to separate function
>   tsnep: Add XDP socket zero-copy RX support
>   tsnep: Add XDP socket zero-copy TX support
> 
>  drivers/net/ethernet/engleder/tsnep.h      |  16 +-
>  drivers/net/ethernet/engleder/tsnep_main.c | 863 ++++++++++++++++++---
>  drivers/net/ethernet/engleder/tsnep_xdp.c  |  66 ++
>  3 files changed, 822 insertions(+), 123 deletions(-)
> 
> -- 
> 2.30.2
>