netdev - Re: [PATCH iwl-net v2] ice: fix receive buffer size miscalculation

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Message-ID: <20230813090313.GG7707@unreal>
Date: Sun, 13 Aug 2023 12:03:13 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>
Subject: Re: [PATCH iwl-net v2] ice: fix receive buffer size miscalculation

On Thu, Aug 10, 2023 at 04:51:10PM -0700, Jesse Brandeburg wrote:
> The driver is misconfiguring the hardware for some values of MTU such that
> it could use multiple descriptors to receive a packet when it could have
> simply used one.
> 
> Change the driver to use a round-up instead of the result of a shift, as
> the shift can truncate the lower bits of the size, and result in the
> problem noted above. It also aligns this driver with similar code in i40e.
> 
> The insidiousness of this problem is that everything works with the wrong
> size, it's just not working as well as it could, as some MTU sizes end up
> using two or more descriptors, and there is no way to tell that is
> happening without looking at ice_trace or a bus analyzer.
> 
> Fixes: efc2214b6047 ("ice: Add support for XDP")
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> ---
> v2: added fixes tag pointing to the last time this line was modified in
> v5.5 instead of pointing back to the introduction of the driver.
> ---
>  drivers/net/ethernet/intel/ice/ice_base.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>