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 F054AC433DB for ; Fri, 5 Mar 2021 18:41:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF647650B1 for ; Fri, 5 Mar 2021 18:41:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229818AbhCESkv (ORCPT ); Fri, 5 Mar 2021 13:40:51 -0500 Received: from gate.crashing.org ([63.228.1.57]:49802 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230047AbhCESk3 (ORCPT ); Fri, 5 Mar 2021 13:40:29 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 125IX2ju027144; Fri, 5 Mar 2021 12:33:02 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 125IX0sO027136; Fri, 5 Mar 2021 12:33:00 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 5 Mar 2021 12:33:00 -0600 From: Segher Boessenkool To: Michael Ellerman Cc: Will Deacon , Christophe Leroy , linux-arch@vger.kernel.org, robh@kernel.org, daniel@gimpelevich.san-francisco.ca.us, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras , linuxppc-dev@lists.ozlabs.org, danielwa@cisco.com Subject: Re: [PATCH v2 1/7] cmdline: Add generic function to build command line. Message-ID: <20210305183300.GX29191@gate.crashing.org> References: <20210303172810.GA19713@willie-the-truck> <20210303174627.GC19713@willie-the-truck> <20210303181651.GE19713@willie-the-truck> <87sg59rewl.fsf@mpe.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87sg59rewl.fsf@mpe.ellerman.id.au> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Fri, Mar 05, 2021 at 10:58:02PM +1100, Michael Ellerman wrote: > Will Deacon writes: > > That's very similar to us; we're not relocated, although we are at least > > in control of the MMU (which is using a temporary set of page-tables). > > prom_init runs as an OF client, with the MMU off (except on some Apple > machines), and we don't own the MMU. So there's really nothing we can do :) You *could* take over all memory mapping. This is complex, and I estimate the change you get this to work correctly on all supported systems to be between -400% and 0%. And not very long later Linux jettisons OF completely anyway. > Though now that I look at it, I don't think we should be doing this > level of commandline handling in prom_init. It should just grab the > value from firmware and pass it to the kernel proper, and then all the > prepend/append/force etc. logic should happen there. That sounds much simpler, yes :-) Segher