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 B9BE6C433DB for ; Fri, 5 Mar 2021 18:37:42 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 2E2FE6509A for ; Fri, 5 Mar 2021 18:37:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E2FE6509A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Dsc105v5hz3dPq for ; Sat, 6 Mar 2021 05:37:40 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Unknown mechanism found: ip:192.40.192.88/32) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4Dsc0d3q1zz30MK for ; Sat, 6 Mar 2021 05:37:21 +1100 (AEDT) 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 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 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, robh@kernel.org, daniel@gimpelevich.san-francisco.ca.us, devicetree@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Paul Mackerras , Will Deacon , danielwa@cisco.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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