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 7BA8FC433DF for ; Fri, 16 Oct 2020 13:17:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 202AC2083B for ; Fri, 16 Oct 2020 13:17:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407391AbgJPNR5 (ORCPT ); Fri, 16 Oct 2020 09:17:57 -0400 Received: from foss.arm.com ([217.140.110.172]:37216 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407363AbgJPNR5 (ORCPT ); Fri, 16 Oct 2020 09:17:57 -0400 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 79AEC1FB; Fri, 16 Oct 2020 06:17:56 -0700 (PDT) Received: from [10.57.50.28] (unknown [10.57.50.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 87CB73F71F; Fri, 16 Oct 2020 06:17:53 -0700 (PDT) Subject: Re: [PATCH] coresight: etm4x: Add config to exclude kernel mode tracing To: Leo Yan Cc: Sai Prakash Ranjan , Denis Nikitin , Mathieu Poirier , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Stephen Boyd , linux-arm-kernel@lists.infradead.org, Mike Leach References: <20201015124522.1876-1-saiprakash.ranjan@codeaurora.org> <20201015160257.GA1450102@xps15> <20201016072401.GC4646@leoy-ThinkPad-X240s> <20201016092450.GG4646@leoy-ThinkPad-X240s> <20201016131407.GA31839@leoy-ThinkPad-X240s> From: Suzuki Poulose Message-ID: <16b3be3a-0d2d-0d0f-24a5-020480ed980c@arm.com> Date: Fri, 16 Oct 2020 14:17:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201016131407.GA31839@leoy-ThinkPad-X240s> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/16/20 2:14 PM, Leo Yan wrote: > On Fri, Oct 16, 2020 at 12:38:47PM +0100, Suzuki Kuruppassery Poulose wrote: > > [...] > >>>> What happens to the sysfs mode of tracing? For that we would still >>>> need a config right to exclude kernel mode tracing completely. >>> >>> IIUC, sysfs mode and perf mode both can apply the same approach, the >>> guest OS runs a thread context for the host, so when a guest OS is >>> switched in or out, the hypervisor can save/restore the context for >>> the guest OS; thus every guest OS will have its dedicated context and >>> trace data ideally. >> >> I don't think Guest Context is something we can support as mentioned >> above, at least for systems without sysreg access for ETMs (and virtualizing >> ETRs is a different story !) > > Thanks for sharing thoughts, Suzuki. > > I missed the device virtulisation. Here should virtualize all devices > (includes CoreSight ETM/funnel/ETR/ETF)? Or only need to virtualize > ETRs? I wouldn't even think of virtualizing the components without sysreg access. So let us not worry about it :-) Cheers Suzuki