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 26F35C001B0 for ; Tue, 8 Aug 2023 16:43:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233312AbjHHQnp (ORCPT ); Tue, 8 Aug 2023 12:43:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233105AbjHHQmz (ORCPT ); Tue, 8 Aug 2023 12:42:55 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6C4516576 for ; Tue, 8 Aug 2023 08:55:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2C6F9624C5 for ; Tue, 8 Aug 2023 11:06:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85065C433C7; Tue, 8 Aug 2023 11:06:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691492800; bh=CrPhcJN57rukfXen+rigaSrwqRSJXsMXj2YdkDgwiGA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NRYvRuUiRxyVy/3To0iBa2lls0LagkDuRwFtnHv2Bxdz+vCKK07I5JbUzE0vh1D1T qAMjURW8XftDij3qDaXfxJP6hzTndfo3UtfKs1XSJb2sHzRukzxGAVUPnJWd6sr5JO kJG3LDKiq7lWOt6T5c7WmLgaJ8/TkmtfbiNvNlue66REmBXb/Q/7CP2lG14aGo0KbI 6uen60MaB8Z5oybh7OVuV1+UzRSUO0WPd8RCCxi4jmCCT0upPEOw7sd1dY9kQjwzP0 bYculYqLVMG38kAykCzmQt/yBKBjNNDjXIZvYIgY4TzIlwgW1LY7nWPSfR1VYR/lM9 Xl5bNj1BBoH5A== Received: from [104.132.45.110] (helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qTKXu-00373o-4P; Tue, 08 Aug 2023 12:06:38 +0100 Date: Tue, 08 Aug 2023 12:06:45 +0100 Message-ID: <87zg31pzcq.wl-maz@kernel.org> From: Marc Zyngier To: Suzuki K Poulose Cc: James Clark , 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 Subject: Re: [RFC PATCH 0/3] coresight: Support exclude_guest with Feat_TRF and nVHE In-Reply-To: References: <20230804101317.460697-1-james.clark@arm.com> <86edki62vz.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.2 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 104.132.45.110 X-SA-Exim-Rcpt-To: suzuki.poulose@arm.com, james.clark@arm.com, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, oliver.upton@linux.dev, james.morse@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, mike.leach@linaro.org, leo.yan@linaro.org, alexander.shishkin@linux.intel.com, anshuman.khandual@arm.com, robh@kernel.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 05 Aug 2023 11:28:39 +0100, Suzuki K Poulose wrote: > > 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. I just quickly reviewed the first two patches of the nVHE series, and I think the shape is a bit wrong. I can absolutely see the interest of preventing extra tracing when a guest is running, but the way this is currently plugged makes it hard to reason about it. > [0] https://lkml.kernel.org/r/20230804085219.260790-1-james.clark@arm.com I'll try to have a look at that one later. Thanks, M. -- Without deviation from the norm, progress is not possible.