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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,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 5A7E0C2D0E4 for ; Fri, 13 Nov 2020 03:17:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0717A20A8B for ; Fri, 13 Nov 2020 03:17:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726276AbgKMDQm (ORCPT ); Thu, 12 Nov 2020 22:16:42 -0500 Received: from foss.arm.com ([217.140.110.172]:60274 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725965AbgKMDQm (ORCPT ); Thu, 12 Nov 2020 22:16:42 -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 75BF51042; Thu, 12 Nov 2020 19:16:41 -0800 (PST) Received: from [10.163.79.120] (unknown [10.163.79.120]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0542F3F6CF; Thu, 12 Nov 2020 19:16:35 -0800 (PST) Subject: Re: [PATCH] arm64: mm: account for hotplug memory when randomizing the linear region To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Will Deacon , linux-kernel@vger.kernel.org, Mark Rutland , Steve Capper , Mark Brown , Marc Zyngier , gshan@redhat.com, Robin Murphy , Steven Price , David Hildenbrand References: <20201014081857.3288-1-ardb@kernel.org> <160503561804.1015659.16599672230432576934.b4-ty@arm.com> <20201112092558.GC29613@gaia> From: Anshuman Khandual Message-ID: <2f0d9bc5-6288-7388-ff10-97198dabac6f@arm.com> Date: Fri, 13 Nov 2020 08:46:27 +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: <20201112092558.GC29613@gaia> 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 11/12/20 2:55 PM, Catalin Marinas wrote: > Hi Anshuman, > > On Wed, Nov 11, 2020 at 09:18:56AM +0530, Anshuman Khandual wrote: >> On 11/11/20 12:44 AM, Catalin Marinas wrote: >>> On Wed, 14 Oct 2020 10:18:57 +0200, Ard Biesheuvel wrote: >>>> As a hardening measure, we currently randomize the placement of >>>> physical memory inside the linear region when KASLR is in effect. >>>> Since the random offset at which to place the available physical >>>> memory inside the linear region is chosen early at boot, it is >>>> based on the memblock description of memory, which does not cover >>>> hotplug memory. The consequence of this is that the randomization >>>> offset may be chosen such that any hotplugged memory located above >>>> memblock_end_of_DRAM() that appears later is pushed off the end of >>>> the linear region, where it cannot be accessed. >>>> >>>> [...] >>> >>> Applied to arm64 (for-next/mem-hotplug), thanks! >>> >>> [1/1] arm64: mm: account for hotplug memory when randomizing the linear region >>> https://git.kernel.org/arm64/c/97d6786e0669 >> >> Got delayed and never made here in time, sorry about that. Nonetheless, >> I have got something working with respect to the generic mechanism that >> David Hildenbrand had asked for earlier. >> >> https://patchwork.kernel.org/project/linux-arm-kernel/patch/1600332402-30123-1-git-send-email-anshuman.khandual@arm.com/ > > There was a lot of discussion around this patch but I haven't seen any > new version posted. Just posted before some time. https://lore.kernel.org/linux-arm-kernel/1605236574-14636-1-git-send-email-anshuman.khandual@arm.com/ > >> I am wondering if we could instead consider merging the above patch with >> a small change that Ard had pointed out earlier [1], I will send out a >> revision if required. > > If your patch fixes the randomisation issue that Ard addressed, I'm > happy to replace that with your patch. But please post a new version and > get some acks in place from the parties involved in the discussion. The above patch is not a replacement for Ard's randomization patch here but rather complements it. Hence both these patches should be considered, which will make memory hotplug better on the platform.