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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 542E4C433E0 for ; Mon, 15 Feb 2021 05:27:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 09B9E64E52 for ; Mon, 15 Feb 2021 05:27:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229779AbhBOF1G (ORCPT ); Mon, 15 Feb 2021 00:27:06 -0500 Received: from foss.arm.com ([217.140.110.172]:58382 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229486AbhBOF1D (ORCPT ); Mon, 15 Feb 2021 00:27:03 -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 C7718101E; Sun, 14 Feb 2021 21:26:16 -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 4487E3F73B; Sun, 14 Feb 2021 21:26:12 -0800 (PST) From: Anshuman Khandual Subject: Re: [PATCH] arm64: mm: correct the start of physical address in linear map To: Pavel Tatashin , tyhicks@linux.microsoft.com, jmorris@namei.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, logang@deltatee.com, ardb@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20210213012316.1525419-1-pasha.tatashin@soleen.com> Message-ID: <06b7bfd1-99cd-a9be-e3cc-9fe13f2cf2a6@arm.com> Date: Mon, 15 Feb 2021 10:56:15 +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: <20210213012316.1525419-1-pasha.tatashin@soleen.com> 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 Hello Pavel, On 2/13/21 6:53 AM, Pavel Tatashin wrote: > Memory hotplug may fail on systems with CONFIG_RANDOMIZE_BASE because the > linear map range is not checked correctly. > > The start physical address that linear map covers can be actually at the > end of the range because of randmomization. Check that and if so reduce it > to 0. Looking at the code, this seems possible if memstart_addr which is a signed value becomes large (after falling below 0) during arm64_memblock_init(). > > This can be verified on QEMU with setting kaslr-seed to ~0ul: > > memstart_offset_seed = 0xffff > START: __pa(_PAGE_OFFSET(vabits_actual)) = ffff9000c0000000 > END: __pa(PAGE_END - 1) = 1000bfffffff > > Signed-off-by: Pavel Tatashin > Fixes: 58284a901b42 ("arm64/mm: Validate hotplug range before creating linear mapping") > --- > arch/arm64/mm/mmu.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index ae0c3d023824..6057ecaea897 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1444,14 +1444,25 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size) > > static bool inside_linear_region(u64 start, u64 size) > { > + u64 start_linear_pa = __pa(_PAGE_OFFSET(vabits_actual)); > + u64 end_linear_pa = __pa(PAGE_END - 1); > + > + /* > + * Check for a wrap, it is possible because of randomized linear mapping > + * the start physical address is actually bigger than the end physical > + * address. In this case set start to zero because [0, end_linear_pa] > + * range must still be able to cover all addressable physical addresses. > + */ If this is possible only with randomized linear mapping, could you please add IS_ENABLED(CONFIG_RANDOMIZED_BASE) during the switch over. Wondering if WARN_ON(start_linear_pa > end_linear_pa) should be added otherwise i.e when linear mapping randomization is not enabled. > + if (start_linear_pa > end_linear_pa) > + start_linear_pa = 0; This looks okay but will double check and give it some more testing. > + > /* > * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)] > * accommodating both its ends but excluding PAGE_END. Max physical > * range which can be mapped inside this linear mapping range, must > * also be derived from its end points. > */ > - return start >= __pa(_PAGE_OFFSET(vabits_actual)) && > - (start + size - 1) <= __pa(PAGE_END - 1); > + return start >= start_linear_pa && (start + size - 1) <= end_linear_pa; > } > > int arch_add_memory(int nid, u64 start, u64 size, > - Anshuman