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Message-ID: <47b79e77-461b-8fe9-41fb-b69a6b205ef2@kernel.org>
Date: Mon, 3 Jul 2023 08:45:38 -0600
From: David Ahern <dsahern@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
Jesper Dangaard Brouer <jbrouer@...hat.com>,
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linux-kernel@...r.kernel.org,
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Leon Romanovsky <leon@...nel.org>,
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AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>,
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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 12:22 AM, Mina Almasry wrote:
> tcpdump is able to access the header of these skbs which is in host
> memory, but not the payload in device memory. Here is an example
> session with my netcat-like test for device memory TCP:
> https://pastebin.com/raw/FRjKf0kv
>
> tcpdump seems to work, and the length of the packets above is correct.
> tcpdump -A however isn't able to print the payload of the packets:
> https://pastebin.com/raw/2PcNxaZV
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?
Thanks for checking.
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