From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta-65-226.siemens.flowmailer.net (mta-65-226.siemens.flowmailer.net [185.136.65.226]) by mail.toke.dk (Postfix) with ESMTPS id C0A72AE08FF for ; Mon, 27 Jan 2025 19:29:37 +0100 (CET) Authentication-Results: mail.toke.dk; dkim=pass (2048-bit key; secure) header.d=siemens.com header.i=florian.bezdeka@siemens.com header.a=rsa-sha256 header.s=fm2 header.b=A1zeyUFF Received: by mta-65-226.siemens.flowmailer.net with ESMTPSA id 20250127182936b13c47a11fee4f4b96 for ; Mon, 27 Jan 2025 19:29:37 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=fm2; d=siemens.com; i=florian.bezdeka@siemens.com; h=Date:From:Subject:To:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:Cc:References:In-Reply-To; bh=6panixb/x0os5ZapLWWRdFuJUYpBXz06VpJ2DjP+mog=; b=A1zeyUFFCuD1/01IlvyP8a7nStl/yDefRzLmN46eDButuHBxshahsCwHerO9PK5bZUwBaa JjuZ5wN8wapbhPC7RQH833+3AZaTuy5Hg9Ykwfzz2qbR4tv9DDUEljsoo1ZPr0Oe7Ctz7mC+ wTnT8ep8aZOaz2/vVNjJtHPEGReehUgGbNGdIiGu/viqY/zVDKE21ZWEMttrkvLeZcasGW7/ bUjQ/l9tUym2erHZPCi2O/EuxulhwAgkra8vG+fKXFKYgN5pwU4OI0YQpq+ElJ/AqKR+EZmY GFEQX2KONvo3NAcX/+vsmHnehfI7eOIDOwh9xoWZpnQY3dJH4fvY2VUg==; Message-ID: <221bb71f7d2464cd566e4a4110423ea56b173cf6.camel@siemens.com> From: Florian Bezdeka To: Jakub Kicinski , Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= Date: Mon, 27 Jan 2025 19:29:35 +0100 In-Reply-To: <20250127100441.0b11e1b8@kernel.org> References: <20250116155350.555374-1-yoong.siang.song@intel.com> <20250116155350.555374-5-yoong.siang.song@intel.com> <87bjvwqvtl.fsf@toke.dk> <20250127100441.0b11e1b8@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Flowmailer-Platform: Siemens Feedback-ID: 519:519-68982:519-21489:flowmailer Message-ID-Hash: OIIQTBWQYYSN4M6SOHIAA7SKDV3PALAW X-Message-ID-Hash: OIIQTBWQYYSN4M6SOHIAA7SKDV3PALAW X-MailFrom: fm-68982-20250127182936b13c47a11fee4f4b96-ar0Ytt@rts-flowmailer.siemens.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Stanislav Fomichev , "Song, Yoong Siang" , "Bouska, Zdenek" , "David S . Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Willem de Bruijn , Donald Hunter , Jonathan Corbet , Bjorn Topel , "Karlsson, Magnus" , "Fijalkowski, Maciej" , Jonathan Lemon , Andrew Lunn , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , "Damato, Joe" , Stanislav Fomichev , Xuan Zhuo , Mina Almasry , Daniel Jurgens , Andrii Nakryiko , Eduard Zingerman , Mykola Lysenko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Shuah Khan , Alexandre Torgue , Jose Abreu , Maxime Coquelin , "Nguyen, Anthony L" , "Kitszel, Przemyslaw" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "linux-stm32@st-md-mailman.stormreply.com" , "linux-arm-kernel@lists.infradead.org" , "intel-wired-lan@lists.osuosl.org" , "xdp-hints@xdp-project.net" X-Mailman-Version: 3.3.10 Precedence: list Subject: [xdp-hints] Re: [PATCH bpf-next v6 4/4] igc: Add launch time support to XDP ZC List-Id: XDP hardware hints design discussion Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Mon, 2025-01-27 at 10:04 -0800, Jakub Kicinski wrote: > On Fri, 24 Jan 2025 12:45:42 +0100 Toke H=C3=B8iland-J=C3=B8rgensen wrote= : > > > > I think there is no simple fix for that. That needs some discussion > > > > around the "expectations" to the headroom / meta data area in front= of > > > > the actual packet data. =20 > > >=20 > > > By 'simple' you mean without some new UAPI to signal the size of that > > > 'reserved area' by the driver? I don't see any other easy way out as = well :-/ =20 > >=20 > > Yeah, I don't think we can impose UAPI restrictions on the metadata are= a > > at this point. I guess the best we can do is to educate users that they > > should call the timestamp kfunc before they modify the metadata? >=20 > I may be misunderstanding the discussion, but I think the answer=20 > is that the driver must be fixed. The metadata-in-prepend problem > also exists for simple adjust head use case, so it existed since > early days of BPF. The driver should copy out (or parse) the metadata > before it invokes the XDP prog. The nfp driver does that. That would have to happen for each packet, without affecting ZC performance. How can that be achieved? So we have at least two drivers with that problem, igc + nfp.=20 My main point: Enabling and implementing ZC (zero copy) mode at one hand, but then starting to copy the meta data for each packet doesn't sound reasonable.