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 724A4C43217 for ; Thu, 1 Dec 2022 08:49:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229852AbiLAItf (ORCPT ); Thu, 1 Dec 2022 03:49:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229933AbiLAItO (ORCPT ); Thu, 1 Dec 2022 03:49:14 -0500 Received: from esa.microchip.iphmx.com (esa.microchip.iphmx.com [68.232.154.123]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E98C8C689; Thu, 1 Dec 2022 00:48:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=microchip.com; i=@microchip.com; q=dns/txt; s=mchp; t=1669884517; x=1701420517; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=e0sGk5FC+bQXFAkQVJL15UcqqaRVlO2Lo1qDc6ms+U8=; b=f9IeOvH49cL2xGrVCDsqD3NlkF76QgXbgm5JbLGgSZKW1BGWGw/viaSP 3sMnyAl/d01sBLKw5pw3zy/1pswMPiBZacLoFqZQBItQjl5Umu6bVZ1wY usUYROYBss8YiDMski8otzHBy6ZbPdaZ+xc+Kb0tSwuU0G9lXaVEMQWed lCHxyp5JbBWXLBCOyDDUMnvd8qSHiZ7FQLK77acwHTcjuXlxp434EigEz bi8olOAbxkeCuSBHAD7zWANWsQ7aprn/OMAcpw/lUOJaGJUpmuCI9iQ4y 1WT2cTndhgaAq1NWqOnTk6SGiCTW85Th5TbtRzfbpflMxOvCjM1ejmR8c g==; X-IronPort-AV: E=Sophos;i="5.96,207,1665471600"; d="scan'208";a="125953620" Received: from unknown (HELO email.microchip.com) ([170.129.1.10]) by esa6.microchip.iphmx.com with ESMTP/TLS/AES256-SHA256; 01 Dec 2022 01:48:36 -0700 Received: from chn-vm-ex03.mchp-main.com (10.10.85.151) by chn-vm-ex03.mchp-main.com (10.10.85.151) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.12; Thu, 1 Dec 2022 01:48:36 -0700 Received: from wendy (10.10.115.15) by chn-vm-ex03.mchp-main.com (10.10.85.151) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.12 via Frontend Transport; Thu, 1 Dec 2022 01:48:34 -0700 Date: Thu, 1 Dec 2022 08:48:15 +0000 From: Conor Dooley To: Andrew Jones CC: Conor Dooley , Palmer Dabbelt , , , , , , , , Subject: Re: [PATCH v1 1/3] RISC-V: clarify ISA string ordering rules in cpu.c Message-ID: References: <20221130234125.2722364-1-conor@kernel.org> <20221130234125.2722364-2-conor@kernel.org> <20221201082743.xjxcnx7zcwycdwy7@kamzik> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20221201082743.xjxcnx7zcwycdwy7@kamzik> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 01, 2022 at 09:27:43AM +0100, Andrew Jones wrote: > On Wed, Nov 30, 2022 at 11:41:24PM +0000, Conor Dooley wrote: > > From: Conor Dooley > > > > While the current list of rules may have been accurate when created > > it now lacks some clarity in the face of isa-manual updates. Instead of > > trying to continuously align this rule-set with the one in the > > specifications, change the role of this comment. > > > > This particular comment is important, as the array it "decorates" > > defines the order in which the ISA string appears to userspace in > > /proc/cpuinfo. > > > > Re-jig and strengthen the wording to provide contributors with a set > > order in which to add entries & note why this particular struct needs > > more attention than others. > > > > While in the area, add some whitespace and tweak some wording for > > readability's sake. > > > > Suggested-by: Andrew Jones > > Signed-off-by: Conor Dooley > > --- > > arch/riscv/kernel/cpu.c | 49 ++++++++++++++++++++++++++++++----------- > > 1 file changed, 36 insertions(+), 13 deletions(-) > > > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c > > index 852ecccd8920..68b2bd0cc3bc 100644 > > --- a/arch/riscv/kernel/cpu.c > > +++ b/arch/riscv/kernel/cpu.c > > @@ -120,22 +120,45 @@ device_initcall(riscv_cpuinfo_init); > > .uprop = #UPROP, \ > > .isa_ext_id = EXTID, \ > > } > > + > > /* > > - * Here are the ordering rules of extension naming defined by RISC-V > > - * specification : > > - * 1. All extensions should be separated from other multi-letter extensions > > - * by an underscore. > > - * 2. The first letter following the 'Z' conventionally indicates the most > > + * The canonical order of ISA extension names in the ISA string is defined in > > + * chapter 27 of the unprivileged specification. > > + * > > + * Ordinarily, for in-kernel data structures, this order is unimportant but > > + * isa_ext_arr defines the order of the ISA string in /proc/cpuinfo. > > + * > > + * The specification uses vague wording, such as should, when it comes to > > + * ordering so for our purposes the following rules apply: > > + * > > + * 1. All multi-letter extensions must be separated from other multi-letter > > 1. All multi-letter extensions must be separated from other extensions by an > underscore. > > (Because we always lead multi-letter extensions with underscore, even the > first one, which follows the single-letter extensions.) Yah, I need to think as if I am using De Morgan's... The DT ABI requires "should" and permits this. The uAPI is "must"/"will" and always has an _. I'll propagate that change to the docs patch too. > > + * extensions by an underscore. > > + * > > + * 2. Additional standard extensions (starting with 'Z') must be sorted after > > + * single-letter extensions and before any higher-privileged extensions. > > + > > + * 3. The first letter following the 'Z' conventionally indicates the most > > * closely related alphabetical extension category, IMAFDQLCBKJTPVH. > > - * If multiple 'Z' extensions are named, they should be ordered first > > - * by category, then alphabetically within a category. > > - * 3. Standard supervisor-level extensions (starts with 'S') should be > > - * listed after standard unprivileged extensions. If multiple > > - * supervisor-level extensions are listed, they should be ordered > > + * If multiple 'Z' extensions are named, they should be ordered first by > > + * category, then alphabetically within a category. > > + * > > + * 3. Standard supervisor-level extensions (starting with 'S') must be listed > > + * after standard unprivileged extensions. If multiple > > + * supervisor-level extensions are listed, they must be ordered > > * alphabetically. > > - * 4. Non-standard extensions (starts with 'X') must be listed after all > > - * standard extensions. They must be separated from other multi-letter > > - * extensions by an underscore. > > + * > > + * 4. Standard machine-level extensions (starting with 'Zxm') must be listed > > + * after any lower-privileged, standard extensions. If multiple > > + * machine-level extensions are listed, they must be ordered > > + * alphabetically. > > + * > > + * 5. Non-standard extensions (starts with 'X') must be listed after all > > + * standard extensions. > ^and alphabetically. "If multiple non-standard extensions are listed, they must be ordered alphabetically." I'll also propagate this to the doc one, if I have not already. > Otherwise, > > Reviewed-by: Andrew Jones Cool. I'll give it a bit before respinning, but I think we are at least getting less ambiguous as time goes on.. Thanks, Conor.