netdev - Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE

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Date: Mon, 3 Jul 2023 11:25:50 -0600
From: David Ahern <dsahern@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Mina Almasry <almasrymina@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Jesper Dangaard Brouer <jbrouer@...hat.com>, brouer@...hat.com,
 Alexander Duyck <alexander.duyck@...il.com>,
 Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net,
 pabeni@...hat.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Lorenzo Bianconi <lorenzo@...nel.org>, Yisen Zhuang
 <yisen.zhuang@...wei.com>, Salil Mehta <salil.mehta@...wei.com>,
 Sunil Goutham <sgoutham@...vell.com>, Geetha sowjanya <gakula@...vell.com>,
 Subbaraya Sundeep <sbhatta@...vell.com>, hariprasad <hkelam@...vell.com>,
 Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
 Felix Fietkau <nbd@....name>, Ryder Lee <ryder.lee@...iatek.com>,
 Shayne Chen <shayne.chen@...iatek.com>, Sean Wang <sean.wang@...iatek.com>,
 Kalle Valo <kvalo@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 Ilias Apalodimas <ilias.apalodimas@...aro.org>, linux-rdma@...r.kernel.org,
 linux-wireless@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, Jonathan Lemon <jonathan.lemon@...il.com>
Subject: Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5]
 page_pool: remove PP_FLAG_PAGE_FRAG flag)

On 7/3/23 11:15 AM, Eric Dumazet wrote:
> On Mon, Jul 3, 2023 at 4:45 PM David Ahern <dsahern@...nel.org> wrote:
> 
>> That is my expectation. The tcpdump is just an easy example of accessing
>> the skb page frags. skb_copy_and_csum_bits used by icmp is another
>> example that can walk frags wanting access to device memory. You did not
>> cause a panic or trip a WARN_ON for example with the tcpdump?
>>
> 
> ICMP packets do not land on the queues having devmem buffers, for
> obvious reasons.

I was not referring to ICMP packets coming in to the nic, but rather an
icmp getting triggered during stack processing.

> 
> Only chosen TCP flows are steered to these queues.

of course.