Received: by 2002:a05:6a10:16a7:0:0:0:0 with SMTP id gp39csp698169pxb; Thu, 19 Nov 2020 11:27:57 -0800 (PST) X-Google-Smtp-Source: ABdhPJyljM4la/QO8E9iTiVyMlfOlQ7Fg0g13j39//Ryf3UYrfTwPYb2KEkrhXTo8YJlj4Pu96OO X-Received: by 2002:a05:6402:cb4:: with SMTP id cn20mr33716476edb.186.1605814077419; Thu, 19 Nov 2020 11:27:57 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1605814077; cv=none; d=google.com; s=arc-20160816; b=i6WxIfN6rAwjf8w69d+gw4Uj9b3AO4Sx95hVWQANtbJsln1OcauQm44PBy240VMULy 1UNZTxyxH/kjvrHo3IMVR637EsJpm5zQYfRMTT5J+fql/IwTmHZOUnFGRUDg/Ic8MaGB 1DIAJ1lHdQKk+LP7MoQJh3YXkSlMf5K1nECpf/DE823/21+zuWs4XOcSNeYXO8fwl3Cv suxrxR3gmyaK29USML4JmtWmf7oYCXnglZXpkOOEpRag2clNecuQwIlI/xTiJO7pJdf/ SWunT/N6+2rsA7jn7aJN/swNBiGY98Y4NHJ9jAeJ9w+DKt+DOV+BU65atxX/iQPS4KiX 9NAA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:user-agent:in-reply-to:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :dkim-signature; bh=mp8bo/mh1qsAicToC1/qubROs1IW9/bS6APBFZkyv1A=; b=rDceM4sG35VYayZgzyY1/HgI6uPeeUkpdqf5THkZkoJJ3m/sUowFaH/hYYJUwZgVhH jAZKIlRAUeYQPSjZUh/n6laB7euIjve97h2RPaX7zRbRyC2CjpK3ZlQltq61zRNSTH9F yNiLNOv1MPwyWz14yITR21a1/h2Sm80X/bQdadj1uWQSSakQGo6eANguH23FANY6uUiV 7FXKhf5PhQYqPMNBqDf6i7jRa3tJSJIpEEQhzyOJ81tRh/tOr2LKh+z+4+YmO24FinlH hrobVfiaMHwa8OHxNirzbStlKj/d2UVjF5y8GWz9ZGcXRFK13nZhFZ1cUY8jF53wmOsW B9KA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=sGeV9Sq+; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id u20si412212edr.287.2020.11.19.11.27.33; Thu, 19 Nov 2020 11:27:57 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=sGeV9Sq+; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727773AbgKSTZ1 (ORCPT + 99 others); Thu, 19 Nov 2020 14:25:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:38228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727189AbgKSTZ1 (ORCPT ); Thu, 19 Nov 2020 14:25:27 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 07A3D221FE; Thu, 19 Nov 2020 19:25:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605813926; bh=kvFfISCJyFCjMPhj33WK+VaqTsHgcbwJDMLEbAjpU/Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sGeV9Sq+F+gYfIx3Km6Q6EeaXCx04wDWHco/rgg+7EjnCcnebcMS0uXNf4B5jCmuE izqTf5VibX7Mbz1NweRMd4gz1uY67fizjX/kYnEdxSd6SdA67r4faUGomMnUodoqvZ tOmloerrJaNWCMZrd36d7w8Vh97a5Zb9Nh4pL+BM= Date: Thu, 19 Nov 2020 19:25:21 +0000 From: Will Deacon To: Tyler Hicks Cc: Catalin Marinas , Pavel Tatashin , Rob Herring , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] arm64: Implement CONFIG_CMDLINE_EXTEND Message-ID: <20201119192520.GC4906@willie-the-truck> References: <20200921191557.350256-1-tyhicks@linux.microsoft.com> <20201103155952.GA4335@sequoia> <20201104120812.GA6632@willie-the-truck> <20201105054009.GA4472@sequoia> <20201105095853.GA7952@willie-the-truck> <20201105152836.GB4472@sequoia> <20201119165612.GB3973@sequoia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201119165612.GB3973@sequoia> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 19, 2020 at 10:56:12AM -0600, Tyler Hicks wrote: > On 2020-11-05 09:28:38, Tyler Hicks wrote: > > On 2020-11-05 09:58:54, Will Deacon wrote: > > > On Wed, Nov 04, 2020 at 11:40:09PM -0600, Tyler Hicks wrote: > > > > On 2020-11-04 12:08:12, Will Deacon wrote: > > > > > On Tue, Nov 03, 2020 at 09:59:52AM -0600, Tyler Hicks wrote: > > > > > > On 2020-09-21 14:15:55, Tyler Hicks wrote: > > > > > > > Provide the CONFIG_CMDLINE_EXTEND config option for arm64 kernels. This > > > > > > > config option can be used to extend the kernel command line parameters, > > > > > > > specified by the bootloader, with additional command line parameters > > > > > > > specified in the kernel configuration. > > > > > > > > > > > > Hi Catalin and Will - Friendly ping on this series now that we're > > > > > > on the other side of the 5.10 merge window. I hope it can be considered > > > > > > for 5.10+1. Let me know if I need to rebase/resubmit. Thanks! > > > > > > > > > > Can you use bootconfig to achieve what you need? > > > > > > > > Thanks for mentioning bootconfig. I hadn't considered it. > > > > > > > > After reading the docs and code, I see a few reasons why I can't use it > > > > out of the box: > > > > > > > > 1) It requires "bootconfig" to be appended to the kernel command line. > > > > My proposed patch series makes it possible to append new options to > > > > the kernel command line in situations where the bootloader is not > > > > interactive. This presents a circular dependency problem for my use > > > > case. > > > > > > > > A new config option could be added to force the enablement of > > > > bootconfig but that would sort of be a single-use duplicate of > > > > CONFIG_CMDLINE_EXTEND's functionality. > > > > > > > > 2) Not all kernel command line options can be configured using > > > > bootconfig. For example, the "nokaslr" and "crashkernel=" parameters > > > > are parsed/handled before setup_boot_config() is called. KASLR can > > > > be disabled via a kernel config change but there's no config option > > > > equivalent for "crashkernel=". Changing the "crashkernel=" command > > > > line option is something that I need to support because a > > > > development/debug kernel build often requires a larger reservation > > > > and we find ourselves adjusting the "crashkernel=" value fairly > > > > often. > > > > > > > > 3) External FIT image build systems do not yet support bootconfig since > > > > it is so new. It is completely fair if you file this away in your > > > > not-my-problem folder but simple kernel config modifications, as > > > > needed for CONFIG_CMDLINE_EXTEND, are something that every image > > > > build system is likely to support today. > > > > > > > > All that said, I do really like the look of bootconfig. Unfortunately, > > > > it doesn't let me achieve everything I need. > > > > > > Ok, well thanks for having a look. A follow-up question I have is how is > > > this handled on x86? They don't appear to have CONFIG_CMDLINE_EXTEND either > > > afaict. Is it because their bootloader story tends to be more uniform? > > > > x86's equivalent was implemented by commit 516cbf3730c4 ("x86, bootup: > > add built-in kernel command line for x86 (v2)"). To summarize, you have > > to enable CONFIG_CMDLINE_BOOL and then that lets you define built-in > > command line parameters in CONFIG_CMDLINE. However, it is backwards in > > that the command line provided by the bootloader is appended onto the > > end of CONFIG_CMDLINE. > > > > This doesn't seem as useful to me because, using the crashkernel= > > example from above, the bootloader provided crashkernel= value may need > > to be overridden by the built-in command line to provide a different > > crashkernel= value for the particular kernel build being booted. Most > > kernel command line parameter parsers are implemented in a way that > > supports multiple instances of the parameter while only honoring the > > last instance. > > Hey Will - Do you any additional concerns that I should look into? No, you convinced me it's useful. I just haven't found time to look at the implementation yet! Will