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=-23.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 B97FCC433DB for ; Sat, 13 Feb 2021 17:53:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85C2664E39 for ; Sat, 13 Feb 2021 17:53:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229829AbhBMRxO (ORCPT ); Sat, 13 Feb 2021 12:53:14 -0500 Received: from linux.microsoft.com ([13.77.154.182]:47760 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229771AbhBMRwt (ORCPT ); Sat, 13 Feb 2021 12:52:49 -0500 Received: from sequoia (162-237-133-238.lightspeed.rcsntx.sbcglobal.net [162.237.133.238]) by linux.microsoft.com (Postfix) with ESMTPSA id 5DE3220B6C40; Sat, 13 Feb 2021 09:52:08 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 5DE3220B6C40 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1613238729; bh=rpYdOjpj1FhPRVoMVuBcX3/kmdKDHEmtzDLETHUirhk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f0x9yRh1W4Z03Eavj5Wvr2Rz9XmndNKoeVjCcJOMKOOLl/qHAe8p9YiEySEkp6R4B bEyLMGpqhIaQoHRq3KvJd0H6oTHjkWYVOHMU5AhCku2e+2PEsemmPE3ugrw4QREGMQ 8jOrWE1lDvRvb0ApTGZd1zbpimF91L+3sUnaGAy8= Date: Sat, 13 Feb 2021 11:51:51 -0600 From: Tyler Hicks To: Pavel Tatashin Cc: jmorris@namei.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, anshuman.khandual@arm.com, rppt@kernel.org, logang@deltatee.com, ardb@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: mm: correct the start of physical address in linear map Message-ID: <20210213175151.GA4646@sequoia> References: <20210213012316.1525419-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210213012316.1525419-1-pasha.tatashin@soleen.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-02-12 20:23:16, 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. > > 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") Tested-by: Tyler Hicks This fixes a memory hot plugging bug that I was seeing on 5.10, with the introduction of 58284a901b42. One comment below... > --- > 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 (start_linear_pa > end_linear_pa) > + start_linear_pa = 0; We're ignoring the portion from the linear mapping's start PA to the point of wraparound. Could the start and end of the hot plugged memory fall within this range and, as a result, the hot plug operation be incorrectly blocked? Tyler > + > /* > * 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, > -- > 2.25.1 >