From patchwork Thu Jun 17 21:27:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= X-Patchwork-Id: 12329607 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57077C49EA5 for ; Thu, 17 Jun 2021 21:37:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DE39613B4 for ; Thu, 17 Jun 2021 21:37:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231468AbhFQVjh (ORCPT ); Thu, 17 Jun 2021 17:39:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:24051 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231346AbhFQVjg (ORCPT ); Thu, 17 Jun 2021 17:39:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623965848; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cJz59YB8g7oLdL+mJzpIs/zDJlYd7kwgcbU7x/ViItE=; b=OLrvLcJPRWOqKsrReXwUvbhvPVmJY+iNlWFuzI7TTPyvIQhfaA+ZF1YO6EzX+H9bbAKLhl 1yK/DyhW89yKI2rF3Wk4B42PzReCX3N+TqM50kOq+Z03IZftjVB4BHRqb3aIJaxm8QHNtZ lIjr2YfHRf9J0tqoS/SGVT28h+cchEs= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-251-pLLRDiEeNVqkD-_KZdAvbg-1; Thu, 17 Jun 2021 17:37:27 -0400 X-MC-Unique: pLLRDiEeNVqkD-_KZdAvbg-1 Received: by mail-ed1-f70.google.com with SMTP id t11-20020a056402524bb029038ffacf1cafso2417008edd.5 for ; Thu, 17 Jun 2021 14:37:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=cJz59YB8g7oLdL+mJzpIs/zDJlYd7kwgcbU7x/ViItE=; b=cXaP4S7jenz7mqWOJaJyhxkaROrtrYsv1HpoYyGKn0d3qe3/UvkKSeRDlOdPnIRhmW q3UGJXrSa+6eqLlRh8twkiqu4GoxhYpyHm7gQLQOzy8087co1qyxHNdRbi9GbqimnrdL mq9cZdlj0xzWBfEOY7KnIifbj+a9SYHcOBDTqHV/hA4NVkCMZ/3EQ4DBLJV1amUdt8py MU075Ap73zsShAoZV6r6dMSiqwRgXOoKHSRuXcclugOQswlHtuFTVH65cExa06KlKs6W i2yZbkEJ8Pla/uAj1FVkteljZ4YcUPQFqCtxyes+JzyHpLxBE9/lJ/yx3Bt2zxthdlXK bZjg== X-Gm-Message-State: AOAM532eSn5sC7yVbHyHvNG4BNVfI9hlpfgvBrkQQP5Pnv60TUnexpoM B6CGgmK28JM+PbMjayBtQg3pcnB3g01oxxOuP8l9UnYpjBNLu0/vmYezoG5Op9sj28olHkQ80bB hGS/4kAtu1hM/ X-Received: by 2002:a17:906:6bd8:: with SMTP id t24mr7529617ejs.501.1623965845819; Thu, 17 Jun 2021 14:37:25 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx7MiYndSZPPnikrer9lLYqdDjZqLkcm6ZdagJQugiaU6quK0vkJPkwzDn0Y2udQcNQ/YaluA== X-Received: by 2002:a17:906:6bd8:: with SMTP id t24mr7529608ejs.501.1623965845672; Thu, 17 Jun 2021 14:37:25 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id f4sm125915ejj.49.2021.06.17.14.37.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Jun 2021 14:37:22 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id A1B4A180730; Thu, 17 Jun 2021 23:27:54 +0200 (CEST) From: =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= To: bpf@vger.kernel.org, netdev@vger.kernel.org Cc: Martin KaFai Lau , Hangbin Liu , Jesper Dangaard Brouer , Magnus Karlsson , "Paul E . McKenney" , Jakub Kicinski , =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , Madalin Bucur , Ioana Ciornei , Ioana Radulescu , Camelia Groza Subject: [PATCH bpf-next v3 07/16] freescale: remove rcu_read_lock() around XDP program invocation Date: Thu, 17 Jun 2021 23:27:39 +0200 Message-Id: <20210617212748.32456-8-toke@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210617212748.32456-1-toke@redhat.com> References: <20210617212748.32456-1-toke@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The dpaa and dpaa2 drivers have rcu_read_lock()/rcu_read_unlock() pairs around XDP program invocations. However, the actual lifetime of the objects referred by the XDP program invocation is longer, all the way through to the call to xdp_do_flush(), making the scope of the rcu_read_lock() too small. This turns out to be harmless because it all happens in a single NAPI poll cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock() misleading. Rather than extend the scope of the rcu_read_lock(), just get rid of it entirely. With the addition of RCU annotations to the XDP_REDIRECT map types that take bh execution into account, lockdep even understands this to be safe, so there's really no reason to keep it around. Cc: Madalin Bucur Cc: Ioana Ciornei Cc: Ioana Radulescu Reviewed-by: Camelia Groza Signed-off-by: Toke Høiland-Jørgensen --- drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 11 ++++------- drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 6 +++--- 2 files changed, 7 insertions(+), 10 deletions(-) diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c index 177c020bf34a..98fdcbde687a 100644 --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c @@ -2558,13 +2558,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr, u32 xdp_act; int err; - rcu_read_lock(); - xdp_prog = READ_ONCE(priv->xdp_prog); - if (!xdp_prog) { - rcu_read_unlock(); + if (!xdp_prog) return XDP_PASS; - } xdp_init_buff(&xdp, DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE, &dpaa_fq->xdp_rxq); @@ -2585,6 +2581,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr, } #endif + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. + */ xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp); /* Update the length and the offset of the FD */ @@ -2638,8 +2637,6 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr, break; } - rcu_read_unlock(); - return xdp_act; } diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c index 8433aa730c42..964d85c9e37d 100644 --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c @@ -352,8 +352,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv, u32 xdp_act = XDP_PASS; int err, offset; - rcu_read_lock(); - xdp_prog = READ_ONCE(ch->xdp.prog); if (!xdp_prog) goto out; @@ -363,6 +361,9 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv, xdp_prepare_buff(&xdp, vaddr + offset, XDP_PACKET_HEADROOM, dpaa2_fd_get_len(fd), false); + /* This code is invoked within a single NAPI poll cycle and thus under + * local_bh_disable(), which provides the needed RCU protection. + */ xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp); /* xdp.data pointer may have changed */ @@ -414,7 +415,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv, ch->xdp.res |= xdp_act; out: - rcu_read_unlock(); return xdp_act; }