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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 E21C3C4743F for ; Mon, 7 Jun 2021 06:19:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C3DD56121D for ; Mon, 7 Jun 2021 06:19:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230191AbhFGGVO (ORCPT ); Mon, 7 Jun 2021 02:21:14 -0400 Received: from verein.lst.de ([213.95.11.211]:44476 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229436AbhFGGVN (ORCPT ); Mon, 7 Jun 2021 02:21:13 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id BD91467373; Mon, 7 Jun 2021 08:19:18 +0200 (CEST) Date: Mon, 7 Jun 2021 08:19:18 +0200 From: Christoph Hellwig To: Nick Kossifidis Cc: guoren@kernel.org, anup.patel@wdc.com, palmerdabbelt@google.com, arnd@arndb.de, wens@csie.org, maxime@cerno.tech, drew@beagleboard.org, liush@allwinnertech.com, lazyparser@gmail.com, wefu@redhat.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-sunxi@lists.linux.dev, Guo Ren , Christoph Hellwig Subject: Re: [RFC PATCH v2 06/11] riscv: pgtable: Add DMA_COHERENT with custom PTE attributes Message-ID: <20210607061918.GA24060@lst.de> References: <1622970249-50770-1-git-send-email-guoren@kernel.org> <1622970249-50770-10-git-send-email-guoren@kernel.org> <610849b6f66e8d5a9653c9f62f46c48d@mailhost.ics.forth.gr> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <610849b6f66e8d5a9653c9f62f46c48d@mailhost.ics.forth.gr> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 06, 2021 at 08:22:14PM +0300, Nick Kossifidis wrote: > This patch violates the Privilege Spec section 4.4.1 that clearly states: > > "Bits63–54 are reserved for future standard use and must be zeroed by > software for forward compatibility" > > Standard use means that valid values can only be defined by the Priv. Spec, > not by the vendor (otherwise they'd be marked as "custom use" or "platform > use"), and since they "must" be zeroed by software we 'll be violating the > Privilege Spec if we do otherwise. Yes, that is why I think it is a no-go.