netdev - Re: [PATCH net-next 3/3] bnxt_en: Let the page pool manage the DMA mapping

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Message-ID: <20230728174212.64000bdc@kernel.org>
Date: Fri, 28 Jul 2023 17:42:12 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Michael Chan <michael.chan@...adcom.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, gospo@...adcom.com, bpf@...r.kernel.org,
 somnath.kotur@...adcom.com, Jesper Dangaard Brouer <hawk@...nel.org>
Subject: Re: [PATCH net-next 3/3] bnxt_en: Let the page pool manage the DMA
 mapping

On Fri, 28 Jul 2023 16:18:29 -0700 Michael Chan wrote:
> +	pp.dma_dir = bp->rx_dir;
> +	pp.max_len = BNXT_RX_PAGE_SIZE;

I _think_ you need PAGE_SIZE here.

This should be smaller than PAGE_SIZE only if you're wasting the rest
of the buffer, e.g. MTU is 3k so you know last 1k will never get used.
PAGE_SIZE is always a multiple of BNXT_RX_PAGE so you waste nothing.

Adding Jesper to CC to keep me honest.

> +	pp.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV;