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 X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 CBF50C34031 for ; Wed, 19 Feb 2020 01:38:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AFBEC24654 for ; Wed, 19 Feb 2020 01:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727743AbgBSBiD (ORCPT ); Tue, 18 Feb 2020 20:38:03 -0500 Received: from mga18.intel.com ([134.134.136.126]:22398 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726655AbgBSBiD (ORCPT ); Tue, 18 Feb 2020 20:38:03 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Feb 2020 17:38:02 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,458,1574150400"; d="scan'208";a="436061496" Received: from vcostago-desk1.jf.intel.com (HELO vcostago-desk1) ([10.54.70.26]) by fmsmga006.fm.intel.com with ESMTP; 18 Feb 2020 17:38:02 -0800 From: Vinicius Costa Gomes To: Thomas Gleixner , LKML Cc: David Miller , bpf@vger.kernel.org, netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Sebastian Sewior , Peter Zijlstra , Clark Williams , Steven Rostedt , Juri Lelli , Ingo Molnar Subject: Re: [RFC patch 09/19] bpf: Use BPF_PROG_RUN_PIN_ON_CPU() at simple call sites. In-Reply-To: <20200214161503.804093748@linutronix.de> References: <20200214133917.304937432@linutronix.de> <20200214161503.804093748@linutronix.de> Date: Tue, 18 Feb 2020 17:39:45 -0800 Message-ID: <87a75ftkwu.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Hi, Thomas Gleixner writes: > From: David Miller > > All of these cases are strictly of the form: > > preempt_disable(); > BPF_PROG_RUN(...); > preempt_enable(); > > Replace this with BPF_PROG_RUN_PIN_ON_CPU() which wraps BPF_PROG_RUN() > with: > > migrate_disable(); > BPF_PROG_RUN(...); > migrate_enable(); > > On non RT enabled kernels this maps to preempt_disable/enable() and on RT > enabled kernels this solely prevents migration, which is sufficient as > there is no requirement to prevent reentrancy to any BPF program from a > preempting task. The only requirement is that the program stays on the same > CPU. > > Therefore, this is a trivially correct transformation. > > [ tglx: Converted to BPF_PROG_RUN_PIN_ON_CPU() ] > > Signed-off-by: David S. Miller > Signed-off-by: Thomas Gleixner > > --- > include/linux/filter.h | 4 +--- > kernel/seccomp.c | 4 +--- > net/core/flow_dissector.c | 4 +--- > net/core/skmsg.c | 8 ++------ > net/kcm/kcmsock.c | 4 +--- > 5 files changed, 6 insertions(+), 18 deletions(-) > > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -713,9 +713,7 @@ static inline u32 bpf_prog_run_clear_cb( > if (unlikely(prog->cb_access)) > memset(cb_data, 0, BPF_SKB_CB_LEN); > > - preempt_disable(); > - res = BPF_PROG_RUN(prog, skb); > - preempt_enable(); > + res = BPF_PROG_RUN_PIN_ON_CPU(prog, skb); > return res; > } > > --- a/kernel/seccomp.c > +++ b/kernel/seccomp.c > @@ -268,16 +268,14 @@ static u32 seccomp_run_filters(const str > * All filters in the list are evaluated and the lowest BPF return > * value always takes priority (ignoring the DATA). > */ > - preempt_disable(); > for (; f; f = f->prev) { > - u32 cur_ret = BPF_PROG_RUN(f->prog, sd); > + u32 cur_ret = BPF_PROG_RUN_PIN_ON_CPU(f->prog, sd); > More a question really, isn't the behavior changing here? i.e. shouldn't migrate_disable()/migrate_enable() be moved to outside the loop? Or is running seccomp filters on different cpus not a problem? -- Vinicius