netdev - Re: [PATCH net-next 4/4] eth: mlx4: use the page pool for Rx buffers

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Message-ID: <20250205111100.4ba5b56f@kernel.org>
Date: Wed, 5 Feb 2025 11:11:00 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Ido Schimmel <idosch@...sch.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org,
 tariqt@...dia.com, hawk@...nel.org
Subject: Re: [PATCH net-next 4/4] eth: mlx4: use the page pool for Rx
 buffers

On Wed, 5 Feb 2025 20:05:27 +0200 Ido Schimmel wrote:
> On Tue, Feb 04, 2025 at 07:12:13PM -0800, Jakub Kicinski wrote:
> > @@ -283,6 +265,7 @@ int mlx4_en_create_rx_ring(struct mlx4_en_priv *priv,
> >  	pp.netdev = priv->dev;
> >  	pp.dev = &mdev->dev->persist->pdev->dev;
> >  	pp.dma_dir = DMA_BIDIRECTIONAL;
> > +	pp.max_len = PAGE_SIZE;  
> 
> Possibly a stupid question, but can you explain this hunk given patch #1
> does not set 'PP_FLAG_DMA_SYNC_DEV' ?

Not sure, I wrote this a while back, I probably left this here 
"for future self", when sync support is added. To remember that
since we still do the page flipping thing we must sync the entire
page, even if MTU is smaller. It's a common source of bugs.