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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 6D848C282C2 for ; Thu, 7 Feb 2019 13:14:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 43A6E2190A for ; Thu, 7 Feb 2019 13:14:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727116AbfBGNOm (ORCPT ); Thu, 7 Feb 2019 08:14:42 -0500 Received: from mga18.intel.com ([134.134.136.126]:16674 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726558AbfBGNOl (ORCPT ); Thu, 7 Feb 2019 08:14:41 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Feb 2019 05:14:41 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,344,1544515200"; d="scan'208";a="113124962" Received: from linux.intel.com ([10.54.29.200]) by orsmga007.jf.intel.com with ESMTP; 07 Feb 2019 05:14:41 -0800 Received: from [10.125.252.152] (abudanko-mobl.ccr.corp.intel.com [10.125.252.152]) by linux.intel.com (Postfix) with ESMTP id 162E25800E0; Thu, 7 Feb 2019 05:14:36 -0800 (PST) From: Alexey Budankov Subject: Re: [PATCH v1 1/3] perf-security: document perf_events/Perf resource control To: Jonathan Corbet Cc: Kees Cook , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Jann Horn , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Alexander Shishkin , Mark Rutland , Andi Kleen , Tvrtko Ursulin , "kernel-hardening@lists.openwall.com" , "linux-doc@vger.kernel.org" , linux-kernel References: <9cfbf7a1-72dd-f9d0-8137-0f120fa74d21@linux.intel.com> <20190206165858.19fdaf58@lwn.net> Organization: Intel Corp. Message-ID: Date: Thu, 7 Feb 2019 16:14:35 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <20190206165858.19fdaf58@lwn.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.02.2019 2:58, Jonathan Corbet wrote: > On Fri, 1 Feb 2019 10:29:11 +0300 > Alexey Budankov wrote: > >> Extend perf-security.rst file with perf_events/Perf resource control >> section describing RLIMIT_NOFILE and perf_event_mlock_kb settings for >> performance monitoring user processes. >> >> Signed-off-by: Alexey Budankov > > Overall these patches seem reasonable, though I have some nits to pick. > I'm happy to apply them but wouldn't mind an ack from the perf camp. > > Alexey, could you wrap your paragraphs at 72-75 columns? Sure, let's have it as the forth patch in the series in order not to mix the actual content with formatting. > >> --- >> Documentation/admin-guide/perf-security.rst | 36 +++++++++++++++++++++ >> 1 file changed, 36 insertions(+) >> >> diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst >> index f73ebfe9bfe2..ff6832191577 100644 >> --- a/Documentation/admin-guide/perf-security.rst >> +++ b/Documentation/admin-guide/perf-security.rst >> @@ -84,6 +84,40 @@ governed by perf_event_paranoid [2]_ setting: >> locking limit is imposed but ignored for unprivileged processes with >> CAP_IPC_LOCK capability. >> >> +perf_events/Perf resource control >> +--------------------------------- >> + >> +perf_events system call API [2]_ allocates file descriptors for every configured > > *The* perf_events system call API Accepted. > >> +PMU event. Open file descriptors are a per-process accountable *resource* governed >> +by RLIMIT_NOFILE [11]_ limit (ulimit -n), which is usually derived from the login > > by *the* RLIMIT_NOFILE Accepted. > >> +shell process. When configuring Perf collection for a long list of events on a >> +large server system, this limit can be easily hit preventing required monitoring >> +configuration. RLIMIT_NOFILE limit can be increased on per-user basis modifying >> +content of limits.conf file [12]_ on some systems. Ordinary Perf sampling session > > of *the* limits.conf file > > Ordinarily, a Perf Accepted. > >> +(perf record) requires an amount of open perf_event file descriptors that is not >> +less than a number of monitored events multiplied by a number of monitored CPUs. >> + >> +An amount of memory available to user processes for capturing performance monitoring >> +data is governed by perf_event_mlock_kb [2]_ setting. This perf_event specific > > by *the* perf_event_mlock_kb Accepted. > >> +*resource* setting defines overall per-cpu limits of memory allowed for mapping > > Why the *emphasis* here? Avoided emphasis here and in the other places of this paragraphs. > >> +by the user processes to execute performance monitoring. The setting essentially >> +extends RLIMIT_MEMLOCK [11]_ limit but only for memory regions mapped specially > > extends *the* RMLIMIT_MEMLOCK limit *,* but only Accepted. > >> +for capturing monitored performance events and related data. >> + >> +For example, if a machine has eight cores and perf_event_mlock_kb limit is set >> +to 516 KiB then a user process is provided with 516 KiB * 8 = 4128 KiB of memory > > Kib, then Comma accepted, Kib = 1024 bits and this is not what is meant here - KiB=1024 Bytes. > >> +above RLIMIT_MEMLOCK limit (ulimit -l) for perf_event mmap buffers. In particular > > above *the* RLIMIT_MEMLOCK > > particular, Accepted. > >> +this means that if the user wants to start two or more performance monitoring > > that, if Accepted. > >> +processes, it is required to manually distribute available 4128 KiB between the > > s/it is/they are/ Not sure what you mean here. I want to say that the users is required to distribute memory among the processes using --mmap-pages. Replaced 'it' with 'the user'. > >> +monitoring processes, for example, using --mmap-pages Perf record mode option. > > using *the* --mmap-pages option Accepted. > >> +Otherwise, the first started performance monitoring process allocates all available >> +4128 KiB and the other processes will fail to proceed due to the lack of memory. >> + >> +RLIMIT_MEMLOCK and perf_event_mlock_kb *resource* constraints are ignored for >> +processes with CAP_IPC_LOCK capability. Thus, perf_events/Perf privileged users > > with *the* CAP_IPC_LOCK Accepted. > >> +can be provided with memory above the constraints for perf_events/Perf performance >> +monitoring purpose by providing the Perf executable with CAP_IPC_LOCK capability. >> + >> Bibliography >> ------------ >> >> @@ -94,4 +128,6 @@ Bibliography >> .. [5] ``_ >> .. [6] ``_ >> .. [7] ``_ >> +.. [11] ``_ >> +.. [12] ``_ > > Thanks, > > jon > Thanks, Alexey