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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 61AC1C4321D for ; Mon, 20 Aug 2018 10:02:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2184720C0C for ; Mon, 20 Aug 2018 10:02:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2184720C0C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726776AbeHTNRV (ORCPT ); Mon, 20 Aug 2018 09:17:21 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:35460 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726030AbeHTNRV (ORCPT ); Mon, 20 Aug 2018 09:17:21 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 67C9380D; Mon, 20 Aug 2018 03:02:23 -0700 (PDT) Received: from [192.168.0.21] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CA5343F2EA; Mon, 20 Aug 2018 03:02:18 -0700 (PDT) Subject: Re: [PATCH v3 0/7] perf: Add ioctl for PMU driver configuration To: Mathieu Poirier , Kim Phillips Cc: Will Deacon , Peter Zijlstra , Arnaldo Carvalho de Melo , Ingo Molnar , Thomas Gleixner , Alexander Shishkin , schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, Mark Rutland , Jiri Olsa , Namhyung Kim , Adrian Hunter , ast@kernel.org, Greg KH , "H. Peter Anvin" , suzuki.poulosi@arm.com, linux-s390@vger.kernel.org, Linux Kernel Mailing List , linux-arm-kernel References: <1531950487-24554-1-git-send-email-mathieu.poirier@linaro.org> <20180813124642.3d49c082a95fc294d926016e@arm.com> <20180814120910.ed225bbc462c58b09e5d68de@arm.com> <20180815093912.GE2427@arm.com> <20180815102820.3520d0c3875d2fd82300cdef@arm.com> From: Suzuki K Poulose Message-ID: <18fe78a3-9a58-cecd-ddb9-d46cbc473b95@arm.com> Date: Mon, 20 Aug 2018 11:03:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: 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 On 08/16/2018 08:28 PM, Mathieu Poirier wrote: > On Wed, 15 Aug 2018 at 09:28, Kim Phillips wrote: >> >> On Wed, 15 Aug 2018 10:39:13 +0100 >> Will Deacon wrote: >> >>> On Tue, Aug 14, 2018 at 01:42:27PM -0600, Mathieu Poirier wrote: >>>> On Tue, 14 Aug 2018 at 11:09, Kim Phillips wrote: >>>>> The other thing that's going on here is that I'm becoming numb to the >>>>> loathsome "failed to mmap with 12 (Cannot allocate memory)" being >>>>> returned no matter what the error is/was. E.g., an error that would >>>>> indicate a sense of non-implementation would be much better >>>>> appreciated than presumably what the above is doing, i.e., returning >>>>> -ENOMEM. That, backed up with specific details in the form of human >>>>> readable text in dmesg would be *most* welcome. >>>> >>>> As part of the refactoring of the code to support CPU-wide scenarios I >>>> intend to emit better diagnostic messages from the driver. Modifying >>>> rb_alloc_aux() to propagate the error message generated by the >>>> architecture specific PMUs doesn't look hard either and I _may_ get to >>>> it as part of this work. >>> >>> For the record, I will continue to oppose PMU drivers that dump diagnostics >>> about user-controlled input into dmesg, but the coresight drivers are yours >>> so it's up to you and I won't get in the way! >> >> That sounds technically self-contradicting to me. Why shouldn't >> coresight share the same policies as those used for PMU drivers? Or >> why not allow the individual vendor PMU driver authors control the >> level of user-friendliness of their own drivers? >> >> That being said, Matheiu, would you accept patches that make coresight >> more verbose in dmesg? > > It depends on the issue you're hoping to address. I'd rather see the > root cause of the problem fixed than adding temporary code. Suzuki > added the ETR perf API and I'm currently working on CPU-wide > scenarios. From there and with regards to what can happen in > setup_aux(), we should have things covered. I think the main issue is the lack of error code propagation from setup_aux() back to the perf_aux_output_handle_begin(), which always return -ENOMEM. If we fix that, we could get better idea of whats wrong. If someone is planning to add verbose messages, they may do so by adding dev_dbg() / pr_debug(), which can be turned on as and when needed. Suzuki