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=-4.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 87434C4338F for ; Mon, 2 Aug 2021 15:46:16 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 54AFC60EE3 for ; Mon, 2 Aug 2021 15:46:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 54AFC60EE3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Pz2JjFMxe4AgZ23p3Zgd3VfK2BqxYg8xa+V1O/ZCMGw=; b=GfMdlad5Jp26hz 7oKaKazOst8NFhOiP6D/wOmwhCDOLdv0NThPlJMQ1TWzJT35JCfuPgkwRzro2rfgnYPZd3SDu9sdO /RRtVXe35HMi25sQ0YZuUmQeNdJI6fmuI6KJElMjXgFvssW2budrE1OUnf3m9GGo96f7pYdirlc3V 9QZVO/eGZPNMQP1/Rj8ooluJepbAKZZ51+AGfynWcbkkQ8nAz8Qkq/eNzQDWydb7rkzcEkbixmesk OecG4acECQdSH91n/5+e4WmSbksOQEeS4UM5BujiR5jyZklu0ZgSuazejKLzMX03/esUdz4XFA9Bl Y0hAPMndT2hsydwamDTA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mAa6x-00H1Mf-SY; Mon, 02 Aug 2021 15:44:16 +0000 Received: from mail-wm1-x32b.google.com ([2a00:1450:4864:20::32b]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mAa6u-00H1LE-3f for linux-arm-kernel@lists.infradead.org; Mon, 02 Aug 2021 15:44:13 +0000 Received: by mail-wm1-x32b.google.com with SMTP id m20-20020a05600c4f54b029024e75a15716so253570wmq.2 for ; Mon, 02 Aug 2021 08:44:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zAWuQ/JvoX+qW03VDGPJ9Ofp3oF3NSH0evX+ItLfT0M=; b=OY1dHlSBGhnSjUiSRde6FOpi/D/J7vDN3qiynTmUlf6bnERXdwDmKC+7PzgqdLk2VQ 6k3GrRyW36WgMN0o5BCwydoFGH4LJ3/Td+yTEL2V0YgpV6njdbtogAPjJdjk3Zbc5vED uxDQrZlBUxtd99jT+x1vQWolvyWpM4AFa8GYKJBYNk9U6K9uhIivv3UR8tFoz+b2YCyd 3+K4ynU4wb5PxA9Sg88UzIdL+uzuohxlpQG0/uGCx/97aBGwwyM9AMyl7xf+OhyBmuOK qWl1yv2dQPqzDtWlA5msz53nVoSicHeDAYeGDn/2tdS/3UYQQB+gKVYy19uWXoVYrYMX vYKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zAWuQ/JvoX+qW03VDGPJ9Ofp3oF3NSH0evX+ItLfT0M=; b=IbdSCXne94gLwDCrhb/Sp+GViQnjY50DRHRYcsr7Nj96kKuFwnljwQl0Ksf5SO3pyV 0WXoDpHsrCY5jZ1P/mCIGj4JknBuIFCo8akkKsA1CKhC5ACalM+WUeK6ZDKMFxLmQs0P EMsUcJjqaqozw860x1rSZfzuak9jz2ksjMBCX8ogd4d91LeYa8S2z1LWig4oL8myByzw AWlbq05d4YUP7cyLlJPb7x7Ksp7an/eGQYZmtzE5S0Z2k5lW9HU4u2dA0Tc0tUqSFHI5 jnk3ZC2EDkVG3A7Ujprpud8/zkHPQJywkwcDnDtplY5xn/4jR21/wS3epsgFRkogfpBw S2RA== X-Gm-Message-State: AOAM531vQcE1wnIJZ0GuF2iHQXJKUrwCP8coe6VMS8soauSEAgqGGdZh AhhOTbS55mW2dE00ktUTQ5/KcKs8dNNKpzgFQeLssg== X-Google-Smtp-Source: ABdhPJwQk3PjsXlhmERVCZwrj08dYks7ZMB1H5WlB2pmNXlDk+r6SlCK3idLXagGaVe4isrMvVOoC3dYiM8MzdRPtiM= X-Received: by 2002:a7b:c0cc:: with SMTP id s12mr49605wmh.0.1627919050360; Mon, 02 Aug 2021 08:44:10 -0700 (PDT) MIME-Version: 1.0 References: <20210721090706.21523-1-james.clark@arm.com> <20210721090706.21523-3-james.clark@arm.com> <20210731060312.GB7437@leoy-ThinkPad-X240s> <20210802150358.GA148327@leoy-ThinkPad-X240s> In-Reply-To: <20210802150358.GA148327@leoy-ThinkPad-X240s> From: Mike Leach Date: Mon, 2 Aug 2021 16:43:59 +0100 Message-ID: Subject: Re: [PATCH 2/6] perf cs-etm: Initialise architecture based on TRCIDR1 To: Leo Yan Cc: James Clark , Arnaldo Carvalho de Melo , Mathieu Poirier , Coresight ML , Al Grant , "Suzuki K. Poulose" , Anshuman Khandual , John Garry , Will Deacon , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel , Linux Kernel Mailing List , linux-perf-users@vger.kernel.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210802_084412_185634_1BC876AB X-CRM114-Status: GOOD ( 54.34 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Leo, On Mon, 2 Aug 2021 at 16:04, Leo Yan wrote: > > Hi Mike, > > On Mon, Aug 02, 2021 at 03:04:14PM +0100, Mike Leach wrote: > > [...] > > > > > > +#define TRCIDR1_TRCARCHMIN_SHIFT 4 > > > > > +#define TRCIDR1_TRCARCHMIN_MASK GENMASK(7, 4) > > > > > +#define TRCIDR1_TRCARCHMIN(x) (((x) & TRCIDR1_TRCARCHMIN_MASK) >> TRCIDR1_TRCARCHMIN_SHIFT) > > > > > +static enum _ocsd_arch_version cs_etm_decoder__get_arch_ver(u32 reg_idr1) > > > > > +{ > > > > > + /* > > > > > + * If the ETM trace minor version is 4 or more then we can assume > > > > > + * the architecture is ARCH_AA64 rather than just V8 > > > > > + */ > > > > > + return TRCIDR1_TRCARCHMIN(reg_idr1) >= 4 ? ARCH_AA64 : ARCH_V8; > > > > > +} > > > > > > > > This is true for ETM4.x & ETE 1.x (arch 5.x) but not ETM 3.x > > > > Probably need to beef up this comment or the function name to emphasise this. > > > > > > Yeah, I think it's good to change the function name. Eventually, this > > > function should only be used for ETM4.x and ETE. > > > > > > Another minor comment is: can we refine the arch version number, e.g. > > > change the OpenCSD's macro "ARCH_AA64" to "ARCH_V8R4", (or > > > "ARCH_V8R3_AA64"), this can give more clear clue what's the ETM version. > > > > > > > The purpose of these macros is to inform the decoder of the > > architecture of the PE - not the version of the ETM. > > > > These OpenCSD macros are defined by the library headers > > (ocsd_if_types.h) and not the perf headers. > > These have been published as the API / ABI for OpenCSD and as such > > changing them affects all OpenCSD clients, not just perf. > > I understand these macros are defined in OpenCSD lib as APIs, since I > saw these macros have not been widely used in perf tool (e.g. > ARCH_AA64), so this is why I think it's good to take chance to refine > the naming conventions. > The macros are used in other tools - so changing now affects those too. Not something I am prepared to do without good reason. > > This PE architecture version is used along with the core profile to > > determine which instructions are valid waypoint instructions to > > associate with atom elements when walking the program image during > > trace decode. > > > > From v8.3 onwards we moved away from filtering on specific > > architecture versions. This was due to two factors:- > > 1. The architectural rules now allow architectural features for one > > increment e.g. Arch 8.4, to be backported into the previous increment > > - e,g, 8.3, which made this filtering more difficult to track. > > 2. After discussion with the PE architects it was clear that > > instructions in a later architect version would not re-use older > > opcodes from a previous one and be nop / invalid in the earlier > > architectures. (certainly in the scope of AA64). Therefore > > the policy in the decoder is to check for all the instructions we know > > about for the latest version of architecture, even if we could be > > decoding an earlier architecture version. This means we may check for > > a few more opcodes than necessary for earlier version of the > > architecture, but the overall decode is more robust and easier to > > maintain. > > > > Therefore for any AA64 core beyond v8.3 - it is safe to use the > > ARCH_AA64 PE architecture version and the decoder will handle it. > > I have no objection for current approach; but two things can cause > confusions and it might be difficult for maintenance: > > - The first thing is now we base on the bit fields TRCIDR1::TRCARCHMIN > to decide the PE architecture version. In the ETMv4 spec, > TRCIDR1::TRCARCHMIN is defined as the trace unit minor version, > so essentially it's a minor version number for tracer (ETM) but not > the PE architecture number. But now we are using it to decide the > PE architecture number (8.3, 8.4, etc...). > This is a slight weakness in the implementation of perf. Ideally one does need to establish the architecture version of the PE - but perf /cs-etm is using an assumption regarding the profile and version of the core, according to the ETM / ETE versiom. That said - the ETM / ETE version numbers do have a strong relationship with PE architecture version numbers, so this assumption holds for the current supported devices. > - The second thing is the macros' naming convention. > E.g. "AA64" gives me an impression it is a general naming "Arm Arch 64" > for all Arm 64-bit CPUs, it's something like an abbreviation for > "aarch64"; so seems to me it doesn't show any meaningful info for PE's > architecture version number. This is why I proposed to use more > explict macro definition for architectures (e.g. ARCH_V8R3, ARCH_V8R4, > ARCH_V9R0, etc). > For modern cores it is sufficient for the decoder to know the profile and that it is aarch 64 - so yes the macro is simply saying this a general AA64 core. The macros for earlier versions are a little more specific as certain filtering is used according to the version of the PE. ARCH_V8R4, ARCH_V9R0 etc would have no significance to the decoder and would not be useful. If we get to the stage where we need more specific PE architecture versions - then these can be added as required. Using the ARCH_AA64 macro means that we do not have to update the API for every version update of the architecture, and there are no changes required to the perf / cs-etm handling. > If we really want to use ARCH_AA64, it's better to give some comments in > the code. > There are comments in the OpenCSD headers, though additional ones in the perf / cs-etm handling soruce code could be added. Regards Mike > Thanks a lot for shared the background info. > > Leo -- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel