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 0E0E4C433EF for ; Mon, 16 May 2022 10:31:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233020AbiEPKb2 (ORCPT ); Mon, 16 May 2022 06:31:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229762AbiEPKbT (ORCPT ); Mon, 16 May 2022 06:31:19 -0400 Received: from gloria.sntech.de (gloria.sntech.de [185.11.138.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED8211837E for ; Mon, 16 May 2022 03:31:15 -0700 (PDT) Received: from ip5b412258.dynamic.kabel-deutschland.de ([91.65.34.88] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nqY08-0001ig-KU; Mon, 16 May 2022 12:30:56 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Christoph Hellwig , Philipp Tomsich Cc: palmer@dabbelt.com, paul.walmsley@sifive.com, aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, wefu@redhat.com, liush@allwinnertech.com, guoren@kernel.org, atishp@atishpatra.org, anup@brainfault.org, drew@beagleboard.org, arnd@arndb.de, wens@csie.org, maxime@cerno.tech, gfavor@ventanamicro.com, andrea.mondelli@huawei.com, behrensj@mit.edu, xinhaoqu@huawei.com, mick@ics.forth.gr, allen.baum@esperantotech.com, jscheid@ventanamicro.com, rtrauben@gmail.com, samuel@sholland.org, cmuellner@linux.com, Wei Wu , Daniel Lustig , Bill Huffman Subject: Re: [PATCH 09/12] riscv: add RISC-V Svpbmt extension support Date: Mon, 16 May 2022 12:30:55 +0200 Message-ID: <4710483.GXAFRqVoOG@diego> In-Reply-To: References: <20220511192921.2223629-1-heiko@sntech.de> <20220516061057.GL12339@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Montag, 16. Mai 2022, 11:09:12 CEST schrieb Philipp Tomsich: > On Mon, 16 May 2022 at 08:11, Christoph Hellwig wrote: > > > > > +config RISCV_ISA_SVPBMT > > > + bool "SVPBMT extension support" > > > > I don't think this prompt is very useful as it doesn't describe > > what it does. But do we even want people to disable it as it is > > really essentially for a fully functioning kernel and a pity that > > it took RISC-V so long to get there? > > Given that RISC-V is (in some ways) an ISA construction set, there > will be valid use cases for embedded users to disable this (e.g. if > they have their own non-standard way to configure these). So while > kernels for binary distributions (and desktop, server, or > general-purpose embedded) will always enable these, I would fully > expect some users to want to turn these off. Also, enabling the SVPBMT extension will pull in the alternative-patching as well of course, and having a way to disable that was a review-request a version in the past. > @Heiko: I would request that we have a longer help text on this, which > explains what it is and ends with the usual "When in doubt, say Y." ok, will do > > > + depends on 64BIT && MMU > > > + select RISCV_ALTERNATIVE > > > + default y > > > + help > > > + Adds support to dynamically detect the presence of the SVPBMT extension > > > > overly long line here. will fix together with Philipp's help-text wish > > > index 5f1046e82d9f..dbfcd9b72bd8 100644 > > > --- a/arch/riscv/include/asm/errata_list.h > > > +++ b/arch/riscv/include/asm/errata_list.h > > > @@ -14,6 +14,9 @@ > > > #define ERRATA_SIFIVE_NUMBER 2 > > > #endif > > > > > > +#define CPUFEATURE_SVPBMT 0 > > > +#define CPUFEATURE_NUMBER 1 > > > > is errata_list.h really the right place for architectural features? That probably stems from the alternatives being exclusively used for erratas in the past. I guess making this "alternative-list.h" might be a better naming? Or are there even better suggestions? > > Otherwise looks good: > > > > Reviewed-by: Christoph Hellwig Thanks Heiko