From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E242AC4332F for ; Mon, 6 Nov 2023 19:34:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232442AbjKFTfA (ORCPT ); Mon, 6 Nov 2023 14:35:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231555AbjKFTe7 (ORCPT ); Mon, 6 Nov 2023 14:34:59 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A4FB183; Mon, 6 Nov 2023 11:34:55 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FA7AC433C9; Mon, 6 Nov 2023 19:34:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699299294; bh=Hl1nfA1hQNe7leKhITV5rp/ybaYc2SObTEPuCoXKzsU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=A19kRBUhdf908QakvSgKid7H5ILLcRyl3LZTCq1N1NbR7P1t/sgJRPyq2mGHLHvNQ c1PmQQF3vJZi27wlDydYRDaG8WnnwIr0O2WZfJhX3FpFS6CHEqJ6CuB7YqBNsWEaZE xyOMV1pLvMG22qoj0QveUa+peLUS08xdNIur+5Fr3xrEIfcoB+ObeLmiFlg1mq0m3q 0yN7lT3Uys4lMsk11MZaPaYEVjqE3WuxO6HHuReiJN0i9RJhbO12h4kRSoBuzqWNjB idZCa47/HKlp/rFMD73n780muQHc7iYP5/kr+yLw9PIA6OnA231CX8KwxAGpxy4SoF Lhij6W8x3MIrw== Message-ID: <19129763-6f74-4b04-8a5f-441255b76d34@kernel.org> Date: Mon, 6 Nov 2023 12:34:52 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v3 09/12] net: add support for skbs with unreadable frags Content-Language: en-US To: Stanislav Fomichev , Mina Almasry Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jesper Dangaard Brouer , Ilias Apalodimas , Arnd Bergmann , Willem de Bruijn , Shuah Khan , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , Shakeel Butt , Jeroen de Borst , Praveen Kaligineedi , Willem de Bruijn , Kaiyuan Zhang References: <20231106024413.2801438-1-almasrymina@google.com> <20231106024413.2801438-10-almasrymina@google.com> From: David Ahern In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 11/6/23 11:47 AM, Stanislav Fomichev wrote: > On 11/05, Mina Almasry wrote: >> For device memory TCP, we expect the skb headers to be available in host >> memory for access, and we expect the skb frags to be in device memory >> and unaccessible to the host. We expect there to be no mixing and >> matching of device memory frags (unaccessible) with host memory frags >> (accessible) in the same skb. >> >> Add a skb->devmem flag which indicates whether the frags in this skb >> are device memory frags or not. >> >> __skb_fill_page_desc() now checks frags added to skbs for page_pool_iovs, >> and marks the skb as skb->devmem accordingly. >> >> Add checks through the network stack to avoid accessing the frags of >> devmem skbs and avoid coalescing devmem skbs with non devmem skbs. >> >> Signed-off-by: Willem de Bruijn >> Signed-off-by: Kaiyuan Zhang >> Signed-off-by: Mina Almasry >> >> --- >> include/linux/skbuff.h | 14 +++++++- >> include/net/tcp.h | 5 +-- >> net/core/datagram.c | 6 ++++ >> net/core/gro.c | 5 ++- >> net/core/skbuff.c | 77 ++++++++++++++++++++++++++++++++++++------ >> net/ipv4/tcp.c | 6 ++++ >> net/ipv4/tcp_input.c | 13 +++++-- >> net/ipv4/tcp_output.c | 5 ++- >> net/packet/af_packet.c | 4 +-- >> 9 files changed, 115 insertions(+), 20 deletions(-) >> >> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h >> index 1fae276c1353..8fb468ff8115 100644 >> --- a/include/linux/skbuff.h >> +++ b/include/linux/skbuff.h >> @@ -805,6 +805,8 @@ typedef unsigned char *sk_buff_data_t; >> * @csum_level: indicates the number of consecutive checksums found in >> * the packet minus one that have been verified as >> * CHECKSUM_UNNECESSARY (max 3) >> + * @devmem: indicates that all the fragments in this skb are backed by >> + * device memory. >> * @dst_pending_confirm: need to confirm neighbour >> * @decrypted: Decrypted SKB >> * @slow_gro: state present at GRO time, slower prepare step required >> @@ -991,7 +993,7 @@ struct sk_buff { >> #if IS_ENABLED(CONFIG_IP_SCTP) >> __u8 csum_not_inet:1; >> #endif >> - >> + __u8 devmem:1; >> #if defined(CONFIG_NET_SCHED) || defined(CONFIG_NET_XGRESS) >> __u16 tc_index; /* traffic control index */ >> #endif >> @@ -1766,6 +1768,12 @@ static inline void skb_zcopy_downgrade_managed(struct sk_buff *skb) >> __skb_zcopy_downgrade_managed(skb); >> } >> >> +/* Return true if frags in this skb are not readable by the host. */ >> +static inline bool skb_frags_not_readable(const struct sk_buff *skb) >> +{ >> + return skb->devmem; > > bikeshedding: should we also rename 'devmem' sk_buff flag to 'not_readable'? > It better communicates the fact that the stack shouldn't dereference the > frags (because it has 'devmem' fragments or for some other potential > future reason). +1. Also, the flag on the skb is an optimization - a high level signal that one or more frags is in unreadable memory. There is no requirement that all of the frags are in the same memory type.