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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 36E5DC433DF for ; Wed, 12 Aug 2020 03:52:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C228207DA for ; Wed, 12 Aug 2020 03:52:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726558AbgHLDwr (ORCPT ); Tue, 11 Aug 2020 23:52:47 -0400 Received: from mga06.intel.com ([134.134.136.31]:43742 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726430AbgHLDwr (ORCPT ); Tue, 11 Aug 2020 23:52:47 -0400 IronPort-SDR: Ek+JBiIB2+U9IDA7xAKKkYQqvjQ4SlwiDzGTCGGlWoFbTi5HCqzszr41VP63Dxg+ZcSfD23EBH xj0snBc2e2yQ== X-IronPort-AV: E=McAfee;i="6000,8403,9710"; a="215399174" X-IronPort-AV: E=Sophos;i="5.76,302,1592895600"; d="scan'208";a="215399174" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Aug 2020 20:52:46 -0700 IronPort-SDR: nJATI7Zrfp6GMtuW+zs9f87Zz9goDjkz4HwXAMP9DwfL6VyYfUMfpZlB/CguyHyef96Y1JcmfK 5xfUaxPR78Uw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,302,1592895600"; d="scan'208";a="324954454" Received: from yjin15-mobl1.ccr.corp.intel.com (HELO [10.238.5.239]) ([10.238.5.239]) by orsmga008.jf.intel.com with ESMTP; 11 Aug 2020 20:52:44 -0700 Subject: Re: [PATCH v1 2/2] perf/core: Fake regs for leaked kernel samples To: Peter Zijlstra Cc: mingo@redhat.com, oleg@redhat.com, acme@kernel.org, jolsa@kernel.org, Linux-kernel@vger.kernel.org, ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com, alexander.shishkin@linux.intel.com, mark.rutland@arm.com, like.xu@linux.intel.com References: <20200731025617.16243-1-yao.jin@linux.intel.com> <20200731025617.16243-2-yao.jin@linux.intel.com> <20200804114900.GI2657@hirez.programming.kicks-ass.net> <4c958d61-11a7-9f3e-9e7d-d733270144a1@linux.intel.com> <20200805124454.GP2657@hirez.programming.kicks-ass.net> <797aa4de-c618-f340-ad7b-cef38c96b035@linux.intel.com> <56957a58-6292-e075-8c30-6230450e3518@linux.intel.com> <20200811075924.GU3982@worktop.programming.kicks-ass.net> <20200811084548.GW3982@worktop.programming.kicks-ass.net> From: "Jin, Yao" Message-ID: <8bedaac0-2db1-b59c-581f-62f6d7a31c48@linux.intel.com> Date: Wed, 12 Aug 2020 11:52:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200811084548.GW3982@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed 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 Hi Peter, On 8/11/2020 4:45 PM, Peter Zijlstra wrote: > On Tue, Aug 11, 2020 at 04:31:10PM +0800, Jin, Yao wrote: >> Hi Peter, >> >> On 8/11/2020 3:59 PM, Peter Zijlstra wrote: >>> On Tue, Aug 11, 2020 at 03:50:43PM +0800, Jin, Yao wrote: >>>> Could I post v2 which basically refers to your patch but removes some >>>> conditions since I see some issues in test if we use these conditions. >>>> >>>> 1. Remove '!event->attr.exclude_hv || !event->attr.exclude_host || >>>> !event->attr.exclude_guest' at the entry of sanitize_sample_regs(). >>>> >>>> 2. Remove '!attr.exclude_hv || !attr.exclude_host || !attr.exclude_guest' >>>> at the perf_event_open syscall entry. >>> >>> exclude_host, maybe -- due to the dodgy semantics of it, but the others >>> should definitely be there. >>> >> >> exclude_guest and exclude_hv are tricky too. >> >> If we do 'perf record -e cycles:u' in both host and guest, we can see: >> >> event->attr.exclude_guest = 0 >> >> thus sanitize_sample_regs() returns regs directly even if exclude_kernel = 1. >> >> And in guest, exclude_hv = 0, it's out of my expectation too. > > I'm confused, how can 'perf record -e cycles:u' _ever_ have > exclude_guest=0, exclude_hv=0 ? That simply makes no sense and is utterly > broken. > > You explicitly ask for userspace-only, reporting hypervisor or guest > events is a straight up bug. > If we run 'perf record -e cycles:u', 1. On host, exclude_guest = 0 and exclude_hv = 1 perf tool doesn't specially set 'exclude_guest' when it parses the 'u' modifier. I agree that can be improved. I will post a perf tool patch to fix that. 2. On guest, exclude_guest = 0 and exclude_hv = 0. For exclude_hv = 0, it looks like a bug but x86 doesn't use exclude_hv. But yes, we should fix that. CC Like Xu . Thanks Jin Yao