netdev - Re: [PATCH net 0/2][pull request] Intel Wired LAN Driver Updates 2022-11-14 (i40e)

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Message-ID: <20221116232121.ahaavt3m6wphxuyw@skbuf>
Date:   Thu, 17 Nov 2022 01:21:21 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, netdev@...r.kernel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
        john.fastabend@...il.com, bpf@...r.kernel.org
Subject: Re: [PATCH net 0/2][pull request] Intel Wired LAN Driver Updates
 2022-11-14 (i40e)

Hi,

On Mon, Nov 14, 2022 at 04:03:22PM -0800, Tony Nguyen wrote:
> This series contains updates to i40e driver only.
> 
> Sylwester removes attempted allocation of Rx buffers when AF_XDP is in Tx
> only mode.
> 
> Bartosz adds helper to calculate Rx buffer length so that it can be
> used when interface is down; before value has been set in struct.
> 
> The following are changes since commit ed1fe1bebe18884b11e5536b5ac42e3a48960835:
>   net: dsa: make dsa_master_ioctl() see through port_hwtstamp_get() shims
> and are available in the git repository at:
>   git://git.kernel.org/pub/scm/linux/kernel/git/tnguy/net-queue 40GbE
> 
> Bartosz Staszewski (1):
>   i40e: fix xdp_redirect logs error message when testing with MTU=1500
> 
> Sylwester Dziedziuch (1):
>   i40e: Fix failure message when XDP is configured in TX only mode
> 
>  drivers/net/ethernet/intel/i40e/i40e_main.c | 48 +++++++++++++++------
>  1 file changed, 34 insertions(+), 14 deletions(-)
> 
> -- 
> 2.35.1
> 

Sorry to interject, but there might be a potential bug I noticed a while
ago in the i40e driver, and I didn't find the occasion to bring it up,
but remembered just now.

Is it correct for i40e_run_xdp_zc() to call i40e_xmit_xdp_tx_ring() on
the XDP_TX action? If I'm reading the code correctly, this will map the
buffer to DMA before sending it. But since this is a zero-copy RX buffer,
it has already been mapped to DMA in i40e_xsk_pool_enable().

Since I don't have the hardware, I can't be 100% sure if I'm following
the code correctly. However if I compare with i40e_xmit_zc(), the latter
does not map buffers to DMA, so I think neither should the former.