linux-kernel - Re: [PATCH v2 bpf] xsk: Fix offset calculation in unaligned mode

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Message-ID: <CAJ8uoz0W1KzYxDzbRk1U3JDr1dgqyS5Da+EFgVrn64-sMeQrJw@mail.gmail.com>
Date: Tue, 22 Apr 2025 11:53:41 +0200
From: Magnus Karlsson <magnus.karlsson@...il.com>
To: "e.kubanski" <e.kubanski@...tner.samsung.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, bjorn@...nel.org, 
	magnus.karlsson@...el.com, maciej.fijalkowski@...el.com, 
	jonathan.lemon@...il.com
Subject: Re: [PATCH v2 bpf] xsk: Fix offset calculation in unaligned mode

On Wed, 16 Apr 2025 at 13:30, e.kubanski <e.kubanski@...tner.samsung.com> wrote:
>
> Bring back previous offset calculation behaviour
> in AF_XDP unaligned umem mode.
>
> In unaligned mode, upper 16 bits should contain
> data offset, lower 48 bits should contain
> only specific chunk location without offset.
>
> Remove pool->headroom duplication into 48bit address.

Thanks Eryk.

Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>

> Signed-off-by: Eryk Kubanski <e.kubanski@...tner.samsung.com>
> Fixes: bea14124bacb ("xsk: Get rid of xdp_buff_xsk::orig_addr")
> ---
>  include/net/xsk_buff_pool.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> index 7f0a75d6563d..b3699a848844 100644
> --- a/include/net/xsk_buff_pool.h
> +++ b/include/net/xsk_buff_pool.h
> @@ -232,8 +232,8 @@ static inline u64 xp_get_handle(struct xdp_buff_xsk *xskb,
>                 return orig_addr;
>
>         offset = xskb->xdp.data - xskb->xdp.data_hard_start;
> -       orig_addr -= offset;
>         offset += pool->headroom;
> +       orig_addr -= offset;
>         return orig_addr + (offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT);
>  }
>
> --
> 2.34.1
>
>