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 663F7EB64DD for ; Sat, 5 Aug 2023 10:29:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229770AbjHEK2u (ORCPT ); Sat, 5 Aug 2023 06:28:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229819AbjHEK2q (ORCPT ); Sat, 5 Aug 2023 06:28:46 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5B4C649CB for ; Sat, 5 Aug 2023 03:28:43 -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 B78DD1FB; Sat, 5 Aug 2023 03:29:25 -0700 (PDT) Received: from [10.57.90.200] (unknown [10.57.90.200]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AF54B3F5A1; Sat, 5 Aug 2023 03:28:40 -0700 (PDT) Message-ID: Date: Sat, 5 Aug 2023 11:28:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [RFC PATCH 0/3] coresight: Support exclude_guest with Feat_TRF and nVHE To: Marc Zyngier , James Clark Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Oliver Upton , James Morse , Zenghui Yu , Catalin Marinas , Will Deacon , Mike Leach , Leo Yan , Alexander Shishkin , Anshuman Khandual , Rob Herring , linux-kernel@vger.kernel.org References: <20230804101317.460697-1-james.clark@arm.com> <86edki62vz.wl-maz@kernel.org> From: Suzuki K Poulose In-Reply-To: <86edki62vz.wl-maz@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Marc On 04/08/2023 20:09, Marc Zyngier wrote: > On Fri, 04 Aug 2023 11:13:10 +0100, > James Clark wrote: >> >> Hi, >> >> I'm looking for help in testing this and for feedback on whether it's >> useful to anyone. Testing it requires hardware that has Feat_TRF (v8.4) >> but no TRBE. This is because TRBE usage is disabled in nVHE guests. >> >> I don't currently have any access to any hardware, and the FVP model >> can only do self hosted trace using TRBE. >> >> Currently with nVHE you would always get trace from guests, and >> filtering out isn't possible without this patchset. In comparison, with >> VHE guests, they never generate guest trace without [1]. I think the >> existence of trace rather than lack of could suggest that this change is >> less useful than [1]. Also the restricted set of hardware that it works >> on supports that too. > > It'd be nice to have some sort of feature parity, but it seems like a > vanishingly small target of users having access to an ETM sink. > >> >> Apart from compilation and checking that the exclude guest settings >> are correctly programmed on guest switch, this is untested by me. > > I'll have a look at the series, but none of my HW fits in this > description (my ARMv8.4+ boxes don't have any form of tracing). While I have your attention, we have another series that manages the trace filtering for Guests on VHE, completely within the Coresight etm4x driver here [0]. I personally think, it is good to have the guest filtering for both nVHE and VHE under the KVM control, like we do in this series. I would like your opinion on this. [0] https://lkml.kernel.org/r/20230804085219.260790-1-james.clark@arm.com Suzuki > > Thanks, > > M. >