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 410D5C433EF for ; Thu, 3 Feb 2022 12:17:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350469AbiBCMRX (ORCPT ); Thu, 3 Feb 2022 07:17:23 -0500 Received: from foss.arm.com ([217.140.110.172]:43324 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241756AbiBCMRW (ORCPT ); Thu, 3 Feb 2022 07:17:22 -0500 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 4AD3311D4; Thu, 3 Feb 2022 04:17:22 -0800 (PST) Received: from [10.163.44.35] (unknown [10.163.44.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1C6D03F774; Thu, 3 Feb 2022 04:17:19 -0800 (PST) Subject: Re: [PATCH] coresight: trbe: Move check for kernelspace unmapped at EL0 to probe To: Sudeep Holla Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mathieu Poirier , Suzuki K Poulose , Mike Leach , Leo Yan , coresight@lists.linaro.org References: <20220201122212.3009461-1-sudeep.holla@arm.com> <01a43ba2-a633-f215-a688-2bda293b5a47@arm.com> <20220203101111.mx3o5kmo2bkjirn4@bogus> From: Anshuman Khandual Message-ID: <8fe55cd3-489c-4826-c3dd-a6a4641c47da@arm.com> Date: Thu, 3 Feb 2022 17:47:15 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20220203101111.mx3o5kmo2bkjirn4@bogus> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/3/22 5:34 PM, Sudeep Holla wrote: >> Could you please add a similar comment like SPE driver regarding how >> the TRBE buffer will be inaccessible, if kernel gets unmapped at EL0 >> and trace capture will terminate. >> > Sure I can add that. But if the device probe fails, will you be able to even > start the trace capture, sorry I didn't get what you mean by "trace capture > will terminate". I assume it must be "trace capture is not possible or not > allowed" IIUC. I guess the comment should be framed like - what might happen if the following code block which checks for arm64_kernel_unmapped_at_el0() is not present. If TRBE gets enabled along with kernel unmapping at EL0 supported, trace capture will terminate.