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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 CD6BBC43457 for ; Fri, 16 Oct 2020 10:30:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 682332084C for ; Fri, 16 Oct 2020 10:30:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="ZynXNCMs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2395303AbgJPKau (ORCPT ); Fri, 16 Oct 2020 06:30:50 -0400 Received: from m42-4.mailgun.net ([69.72.42.4]:12297 "EHLO m42-4.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389536AbgJPKas (ORCPT ); Fri, 16 Oct 2020 06:30:48 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1602844247; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=MBBTz+wbATBpIcOHVoqb2HLcX9i5i5/HpFr5H1lz7UY=; b=ZynXNCMsxqq6J7M8zHHNFObXUdjvX7MGXV9KnZwXJ5NevORKTV8G7gFhtKLQi38qn75mcPaX WL6FaewAhdgU1lK2sBi7Vupok3ChrYNSE8NpVsg+C4U6le4gOmGtbmDiGJ2j3/nlLbp1NSSK aFY60KeKCmSWJQjwK6MKSMATN/A= X-Mailgun-Sending-Ip: 69.72.42.4 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n01.prod.us-west-2.postgun.com with SMTP id 5f89765706d81bc48d016215 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Fri, 16 Oct 2020 10:30:47 GMT Sender: saiprakash.ranjan=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 60C47C43382; Fri, 16 Oct 2020 10:30:47 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id C25CFC433CB; Fri, 16 Oct 2020 10:30:46 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Fri, 16 Oct 2020 16:00:46 +0530 From: Sai Prakash Ranjan To: Leo Yan Cc: Denis Nikitin , Mathieu Poirier , Suzuki K Poulose , 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 Subject: Re: [PATCH] coresight: etm4x: Add config to exclude kernel mode tracing In-Reply-To: <20201016092450.GG4646@leoy-ThinkPad-X240s> References: <20201015124522.1876-1-saiprakash.ranjan@codeaurora.org> <20201015160257.GA1450102@xps15> <20201016072401.GC4646@leoy-ThinkPad-X240s> <20201016092450.GG4646@leoy-ThinkPad-X240s> Message-ID: X-Sender: saiprakash.ranjan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Leo, On 2020-10-16 14:54, Leo Yan wrote: > Hi Sai, > > On Fri, Oct 16, 2020 at 02:10:47PM +0530, Sai Prakash Ranjan wrote: >> Hi Leo, >> >> On 2020-10-16 12:54, Leo Yan wrote: >> > On Thu, Oct 15, 2020 at 11:40:05PM -0700, Denis Nikitin wrote: >> > > Hi Mathieu, >> > > >> > > I think one of the use cases could be VMs. >> > > Is there isolation between EL1 guest kernels which we can control >> > > from perf >> > > in a system wide mode? >> > >> > Sorry for suddenly jumping in. >> > >> > For KVM, I think we need to implement mechanism for saving/restoring >> > CoreSight context for every guest OS, the CPU PMUs has implemented >> > related features [1]. >> > >> > Thanks, >> > Leo >> > >> > [1] >> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kvm/pmu.c >> > >> >> 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. > Thanks for the explanation, so for this usecase then we would have to implement something as you suggested, not sure how hard would that be looking at my KVM knowledge(which at the moment is almost nil) when compared to a kconfig ;) Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation