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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 9AAA6C433DB for ; Tue, 16 Feb 2021 03:13:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D96064DF0 for ; Tue, 16 Feb 2021 03:13:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229889AbhBPDMt (ORCPT ); Mon, 15 Feb 2021 22:12:49 -0500 Received: from foss.arm.com ([217.140.110.172]:53770 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229708AbhBPDMq (ORCPT ); Mon, 15 Feb 2021 22:12:46 -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 0C92631B; Mon, 15 Feb 2021 19:12:01 -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 9CFCF3F73D; Mon, 15 Feb 2021 19:11:57 -0800 (PST) Subject: Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check To: Pavel Tatashin , Ard Biesheuvel Cc: Tyler Hicks , James Morris , Catalin Marinas , Will Deacon , Andrew Morton , Mike Rapoport , Logan Gunthorpe , Linux ARM , Linux Kernel Mailing List References: <20210215192237.362706-1-pasha.tatashin@soleen.com> <20210215192237.362706-2-pasha.tatashin@soleen.com> From: Anshuman Khandual Message-ID: <1790afff-eebd-1eda-a1b4-0062908f1f32@arm.com> Date: Tue, 16 Feb 2021 08:42:26 +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: 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 2/16/21 1:21 AM, Pavel Tatashin wrote: > On Mon, Feb 15, 2021 at 2:34 PM Ard Biesheuvel wrote: >> >> On Mon, 15 Feb 2021 at 20:30, Pavel Tatashin wrote: >>> >>>> Can't we simply use signed arithmetic here? This expression works fine >>>> if the quantities are all interpreted as s64 instead of u64 >>> >>> I was thinking about that, but I do not like the idea of using sign >>> arithmetics for physical addresses. Also, I am worried that someone in >>> the future will unknowingly change it to unsigns or to phys_addr_t. It >>> is safer to have start explicitly set to 0 in case of wrap. >> >> memstart_addr is already a s64 for this exact reason. > > memstart_addr is basically an offset and it must be negative. For > example, this would not work if it was not signed: > #define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT)) > > However, on powerpc it is phys_addr_t type. > >> >> Btw, the KASLR check is incorrect: memstart_addr could also be >> negative when running the 52-bit VA kernel on hardware that is only >> 48-bit VA capable. > > Good point! > > if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) > memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52); > > So, I will remove IS_ENABLED(CONFIG_RANDOMIZE_BASE) again. > > I am OK to change start_linear_pa, end_linear_pa to signed, but IMO > what I have now is actually safer to make sure that does not break > again in the future. An explicit check for the flip over and providing two different start addresses points would be required in order to use the new framework. 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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 A3FC8C433E0 for ; Tue, 16 Feb 2021 03:13:38 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 66CCC64D9D for ; Tue, 16 Feb 2021 03:13:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66CCC64D9D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=HNU2r3T4skahYObzBYUIKHUWzxAtSqvJKEvIkojb/iY=; b=Ho9YmOnve+IKwLxV+CAEKwOfd iC1AiuhHHhPPzWpOrxVYMmsK5c2Zyg0r1zPjZ//2IKjjJWi1B8WgFNJlYa4sgVI1VdLm1Q17thdzR GTIBtUIiblwJLZW/HUP7e1aXJL0yYuxi45641ru103VhUwO1FxgghQ9wP56dg2BzSKbuHlYOchlQU nioAaRHqYi9YNrjzybeqIS2tRODDNPrvaBlGoOfKM3YRferONhXXKuH19KACWJ143O2msDEBXeg5M Kzc2xIDfuosvCcVlOZ0trZibqG3p0CTEAObRvxaFFporzpirpgySTJuD6TIw8hVdNJLT/9VWJ7UK9 NefqdL/kw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lBqmU-0000WP-JC; Tue, 16 Feb 2021 03:12:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lBqmS-0000W3-W5 for linux-arm-kernel@lists.infradead.org; Tue, 16 Feb 2021 03:12:05 +0000 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 0C92631B; Mon, 15 Feb 2021 19:12:01 -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 9CFCF3F73D; Mon, 15 Feb 2021 19:11:57 -0800 (PST) Subject: Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check To: Pavel Tatashin , Ard Biesheuvel References: <20210215192237.362706-1-pasha.tatashin@soleen.com> <20210215192237.362706-2-pasha.tatashin@soleen.com> From: Anshuman Khandual Message-ID: <1790afff-eebd-1eda-a1b4-0062908f1f32@arm.com> Date: Tue, 16 Feb 2021 08:42:26 +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: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210215_221205_114278_D06C6BC5 X-CRM114-Status: GOOD ( 21.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , James Morris , Linux Kernel Mailing List , Logan Gunthorpe , Tyler Hicks , Linux ARM , Andrew Morton , Will Deacon , Mike Rapoport Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/16/21 1:21 AM, Pavel Tatashin wrote: > On Mon, Feb 15, 2021 at 2:34 PM Ard Biesheuvel wrote: >> >> On Mon, 15 Feb 2021 at 20:30, Pavel Tatashin wrote: >>> >>>> Can't we simply use signed arithmetic here? This expression works fine >>>> if the quantities are all interpreted as s64 instead of u64 >>> >>> I was thinking about that, but I do not like the idea of using sign >>> arithmetics for physical addresses. Also, I am worried that someone in >>> the future will unknowingly change it to unsigns or to phys_addr_t. It >>> is safer to have start explicitly set to 0 in case of wrap. >> >> memstart_addr is already a s64 for this exact reason. > > memstart_addr is basically an offset and it must be negative. For > example, this would not work if it was not signed: > #define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT)) > > However, on powerpc it is phys_addr_t type. > >> >> Btw, the KASLR check is incorrect: memstart_addr could also be >> negative when running the 52-bit VA kernel on hardware that is only >> 48-bit VA capable. > > Good point! > > if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) > memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52); > > So, I will remove IS_ENABLED(CONFIG_RANDOMIZE_BASE) again. > > I am OK to change start_linear_pa, end_linear_pa to signed, but IMO > what I have now is actually safer to make sure that does not break > again in the future. An explicit check for the flip over and providing two different start addresses points would be required in order to use the new framework. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel