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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2823EE6457 for ; Fri, 15 Sep 2023 13:50:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234760AbjIONus (ORCPT ); Fri, 15 Sep 2023 09:50:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54310 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234618AbjIONup (ORCPT ); Fri, 15 Sep 2023 09:50:45 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 48D791FF5; Fri, 15 Sep 2023 06:50:39 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 48AA91FB; Fri, 15 Sep 2023 06:51:16 -0700 (PDT) Received: from [192.168.1.3] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5A5D73F67D; Fri, 15 Sep 2023 06:50:37 -0700 (PDT) Message-ID: Date: Fri, 15 Sep 2023 14:50:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [RFC PATCH v3 0/8] Coresight for Kernel panic and watchdog reset Content-Language: en-US To: Linu Cherian , suzuki.poulose@arm.com, mike.leach@linaro.org, leo.yan@linaro.org Cc: linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, devicetree@vger.kernel.org, sgoutham@marvell.com, gcherian@marvell.com References: <20230904050548.28047-1-lcherian@marvell.com> From: James Clark In-Reply-To: <20230904050548.28047-1-lcherian@marvell.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/09/2023 06:05, Linu Cherian wrote: > This RFC v3 patch series is rebased on v6.5-rc7 and is dependent > on the below two patches. [...] > > Steps for reading trace data captured in previous boot > ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1. cd /sys/bus/coresight/devices/tmc_etrXX/ > > 2. Change to special mode called, read_prevboot. > > #echo 1 > read_prevboot > > 3. Dump trace buffer data to a file, > > #dd if=/dev/tmc_etrXX of=~/cstrace.bin Hi Linu, I left this comment on V2, but I tested it again and get the same result. Instead of linking it I'll just re-paste it here: I made a reserved region, but when I run this command I get "Unable to handle kernel paging request at virtual address 001f1921ed10ffae". Is there an extra step involved if there was no trace captured from a previous panic? I thought I'd just be able to read out uninitialised data. Or is it the uninitialised metadata that's causing this issue? Also that's without KASAN or lockdep turned on. If I have a kernel with either of those things I get a different warning for each one. I expect the lockdep one would happen even in the working scenario though? > > 4. Reset back to normal mode > > #echo 0 > read_prevboot >