From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B0D34249EE; Wed, 29 Nov 2023 16:49:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="StjyrXWy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F708C433C7; Wed, 29 Nov 2023 16:49:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701276555; bh=aEv5kpjb2fy64cYuodJOoUVmTw2NUs12Hxb5UlfaW3E=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=StjyrXWyiwn3V6abNqHXOwTYc6k6M1i/hxwztuIHvIl/d3UCAtPsusDnFs0vl5JaD 8iVIJGesZpMV+S0UzBiiRCA1CFb7o3EnWhLqIMnkyHHV8HkkV3ugo0pl8iopMWdFdC 4N0DAJDbJXFkTh8LaVJdHJSkeQQCMd6d6w2cNVjOoLE5wwFY2zVHW4fSm9AIF0HOnY swHNNc7EZegQGlzygN+uTzGxR5er+Hs/WIY81IIANw5dD4Tpr9+xmGHEEnAwYtzmkR mRhe7QKiG8moNJJDLLY9HC+J1DFz0J3yufG2J9vVyub3/h5nn4xCl9E9CEne7AHqWS +nrluRMbiOjqg== Date: Wed, 29 Nov 2023 08:49:13 -0800 From: Jakub Kicinski To: Stanislav Fomichev Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org, toke@kernel.org, willemb@google.com, dsahern@kernel.org, magnus.karlsson@intel.com, bjorn@kernel.org, maciej.fijalkowski@intel.com, hawk@kernel.org, yoong.siang.song@intel.com, netdev@vger.kernel.org, xdp-hints@xdp-project.net Subject: Re: [PATCH bpf-next v6 02/13] xsk: Add TX timestamp and TX checksum offload support Message-ID: <20231129084913.01dc63c2@kernel.org> In-Reply-To: <20231127190319.1190813-3-sdf@google.com> References: <20231127190319.1190813-1-sdf@google.com> <20231127190319.1190813-3-sdf@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 27 Nov 2023 11:03:08 -0800 Stanislav Fomichev wrote: > This change actually defines the (initial) metadata layout > that should be used by AF_XDP userspace (xsk_tx_metadata). > The first field is flags which requests appropriate offloads, > followed by the offload-specific fields. The supported per-device > offloads are exported via netlink (new xsk-flags). > > The offloads themselves are still implemented in a bit of a > framework-y fashion that's left from my initial kfunc attempt. > I'm introducing new xsk_tx_metadata_ops which drivers are > supposed to implement. The drivers are also supposed > to call xsk_tx_metadata_request/xsk_tx_metadata_complete in > the right places. Since xsk_tx_metadata_{request,_complete} > are static inline, we don't incur any extra overhead doing > indirect calls. > > The benefit of this scheme is as follows: > - keeps all metadata layout parsing away from driver code > - makes it easy to grep and see which drivers implement what > - don't need any extra flags to maintain to keep track of what > offloads are implemented; if the callback is implemented - the offload > is supported (used by netlink reporting code) > > Two offloads are defined right now: > 1. XDP_TXMD_FLAGS_CHECKSUM: skb-style csum_start+csum_offset > 2. XDP_TXMD_FLAGS_TIMESTAMP: writes TX timestamp back into metadata > area upon completion (tx_timestamp field) > > XDP_TXMD_FLAGS_TIMESTAMP is also implemented for XDP_COPY mode: it writes > SW timestamp from the skb destructor (note I'm reusing hwtstamps to pass > metadata pointer). > > The struct is forward-compatible and can be extended in the future > by appending more fields. Acked-by: Jakub Kicinski