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=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 E9357C433E0 for ; Thu, 11 Feb 2021 12:14:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 97A0A64E95 for ; Thu, 11 Feb 2021 12:14:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230386AbhBKMN4 (ORCPT ); Thu, 11 Feb 2021 07:13:56 -0500 Received: from foss.arm.com ([217.140.110.172]:51092 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229712AbhBKMLH (ORCPT ); Thu, 11 Feb 2021 07:11:07 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D6301063; Thu, 11 Feb 2021 04:10:12 -0800 (PST) Received: from [192.168.0.130] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 73EA03F73B; Thu, 11 Feb 2021 04:10:08 -0800 (PST) Subject: Re: [PATCH V2 1/2] arm64/mm: Fix pfn_valid() for ZONE_DEVICE based memory To: Will Deacon Cc: Mark Rutland , David Hildenbrand , Catalin Marinas , linux-kernel@vger.kernel.org, Mike Rapoport , linux-mm@kvack.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , James Morse , Dan Williams , Robin Murphy , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org References: <1612239114-28428-1-git-send-email-anshuman.khandual@arm.com> <1612239114-28428-2-git-send-email-anshuman.khandual@arm.com> <20210202123215.GA16868@willie-the-truck> <20210202123524.GB16868@willie-the-truck> <20210202125152.GC16868@willie-the-truck> <4d8f5156-8628-5531-1485-322ad92aa15c@redhat.com> <0e649f28-4d54-319d-f876-8a93870cda7f@arm.com> <20210205185552.GA23216@willie-the-truck> <20210211115354.GB29894@willie-the-truck> From: Anshuman Khandual Message-ID: <23e5eb93-a39c-c68e-eac1-c5ccf9036079@arm.com> Date: Thu, 11 Feb 2021 17:40:35 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210211115354.GB29894@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/11/21 5:23 PM, Will Deacon wrote: > On Fri, Feb 05, 2021 at 06:55:53PM +0000, Will Deacon wrote: >> On Wed, Feb 03, 2021 at 09:20:39AM +0530, Anshuman Khandual wrote: >>> On 2/2/21 6:26 PM, David Hildenbrand wrote: >>>> On 02.02.21 13:51, Will Deacon wrote: >>>>> On Tue, Feb 02, 2021 at 01:39:29PM +0100, David Hildenbrand wrote: >>>>>> As I expressed already, long term we should really get rid of the arm64 >>>>>> variant and rather special-case the generic one. Then we won't go out of >>>>>> sync - just as it happened with ZONE_DEVICE handling here. >>>>> >>>>> Why does this have to be long term? This ZONE_DEVICE stuff could be the >>>>> carrot on the stick :) >>>> >>>> Yes, I suggested to do it now, but Anshuman convinced me that doing a >>>> simple fix upfront might be cleaner --- for example when it comes to >>>> backporting :) >>> >>> Right. The current pfn_valid() breaks for ZONE_DEVICE memory and this fixes >>> the problem in the present context which can be easily backported if required. >>> >>> Changing or rather overhauling the generic code with new configs as proposed >>> earlier (which I am planning to work on subsequently) would definitely be an >>> improvement for the current pfn_valid() situation in terms of maintainability >>> but then it should not stop us from fixing the problem now. >> >> Alright, I've mulled this over a bit. I don't agree that this patch helps >> with maintainability (quite the opposite, in fact), but perfection is the >> enemy of the good so I'll queue the series for 5.12. However, I'll revert >> the changes at the first sign of a problem, so please do work towards a >> generic solution which can replace this in the medium term. > > ... and dropped. These patches appear to be responsible for a boot > regression reported by CKI: Ahh, boot regression ? These patches only change the behaviour for non boot memory only. > > https://lore.kernel.org/r/cki.8D1CB60FEC.K6NJMEFQPV@redhat.com Will look into the logs and see if there is something pointing to the problem.