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=-8.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 BCC04C433E0 for ; Thu, 11 Feb 2021 12:25:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 815E764D73 for ; Thu, 11 Feb 2021 12:25:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231767AbhBKMZZ (ORCPT ); Thu, 11 Feb 2021 07:25:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:49206 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230420AbhBKMXB (ORCPT ); Thu, 11 Feb 2021 07:23:01 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id BDE0964E9A; Thu, 11 Feb 2021 12:21:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613046108; bh=o3YtiUDjeinRUlnclOK4o3qUHnz1oyjiknS7o6mlojU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MovGASDhlPuy0OGL9HveOomvFFWZOx3I4EpxBWaKS6XvXdfrFmfkpoZJeky09CoXk k5jC6nBKAHPNa0YfmIQ4AGEg3XhZkJKUYZ5xS7QphKa9WkvpGGI0z020DzApjnX9Vi fUVZPt2baXxhlqpd4/Dlph55KkomG+0dei+Rd1CFxHhUzHthMYoPgCRD29M6kHCco6 kHzMSY0ICFH2HP6xrtjlyV304n9Y711WMcuV+OoFbMJPxLcnJ0xi5GdWexFn1yF+1z pmj8K8Ho0R6vx73nQRj4/nHI1wAHiNfQPVGKBErgyce58PZ024j5Ddy7zhQVT2lE66 +HBHVpHSyBMYA== Date: Thu, 11 Feb 2021 12:21:43 +0000 From: Will Deacon To: Anshuman Khandual Cc: Mark Rutland , David Hildenbrand , Catalin Marinas , linux-kernel@vger.kernel.org, Mike Rapoport , linux-mm@kvack.org, =?iso-8859-1?B?Suly9G1l?= Glisse , James Morse , Dan Williams , Robin Murphy , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH V2 1/2] arm64/mm: Fix pfn_valid() for ZONE_DEVICE based memory Message-ID: <20210211122143.GC29894@willie-the-truck> References: <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> <23e5eb93-a39c-c68e-eac1-c5ccf9036079@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <23e5eb93-a39c-c68e-eac1-c5ccf9036079@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 11, 2021 at 05:40:35PM +0530, Anshuman Khandual wrote: > 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. Sure, but this thing is horribly fragile, which is why I was nervous about touching it in the first place ;) > > 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. We don't have a log yet, but I've asked whether earlycon works on the problematic machine (the failure seems to be specific to a certain TX2). Either way, this is too late for 5.12 now. Will