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=ham 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 07670C433DB for ; Thu, 11 Feb 2021 11:54:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7E51264EAC for ; Thu, 11 Feb 2021 11:54:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E51264EAC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F1AE66B00D4; Thu, 11 Feb 2021 06:54:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ECB5D6B00D5; Thu, 11 Feb 2021 06:54:01 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D91566B00D6; Thu, 11 Feb 2021 06:54:01 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0201.hostedemail.com [216.40.44.201]) by kanga.kvack.org (Postfix) with ESMTP id BCFE76B00D4 for ; Thu, 11 Feb 2021 06:54:01 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 8A1D9181AEF09 for ; Thu, 11 Feb 2021 11:54:01 +0000 (UTC) X-FDA: 77805828282.09.jam74_4f12ab827618 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id 6D04A180AD815 for ; Thu, 11 Feb 2021 11:54:01 +0000 (UTC) X-HE-Tag: jam74_4f12ab827618 X-Filterd-Recvd-Size: 4124 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Thu, 11 Feb 2021 11:54:00 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 9248264E6F; Thu, 11 Feb 2021 11:53:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613044439; bh=gicVhM+wtkSMREjoHbBuY4IMQqDkvxQMpAmUQL2bdt4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AkD8I8ftAHIQToJb6OooX5MqichnZBQ8UXr5PjaBmx9wjmdGLu53x9urtnhYcEM/z x61sCP0wQw4L/NQrwMk7gW6dh7uui15R7Y0SOJdZx6D25CW2TO9/8X/6igJ1HRy8bP nF831tJdAk/emaXJS5LD0qy4xYJDTgybrg4nmucIk4z6FDeAFcN6cratVQb7Ylzu4Z lW5RaztVRcenUHI1C/t/pzotbIsW9WmhxIhUakgKPZ826k3D9kD8kqWGJat+kc7XXR SGGx7TzmWEavPQw8qSBCFchk5oMoygCwqIJ5xGFLVmonwuXTY65bXFcJh03lSeQfds S6B6FVKmgev2A== Date: Thu, 11 Feb 2021 11:53:54 +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: <20210211115354.GB29894@willie-the-truck> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210205185552.GA23216@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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: https://lore.kernel.org/r/cki.8D1CB60FEC.K6NJMEFQPV@redhat.com Will