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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 C02C6C43381 for ; Mon, 25 Feb 2019 09:45:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 837772084D for ; Mon, 25 Feb 2019 09:45:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="ihZGzOlx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726613AbfBYJp1 (ORCPT ); Mon, 25 Feb 2019 04:45:27 -0500 Received: from mail.skyhub.de ([5.9.137.197]:36490 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726315AbfBYJp0 (ORCPT ); Mon, 25 Feb 2019 04:45:26 -0500 Received: from zn.tnic (p200300EC2BC68000F50265612EF4EB95.dip0.t-ipconnect.de [IPv6:2003:ec:2bc6:8000:f502:6561:2ef4:eb95]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 81E471EC0253; Mon, 25 Feb 2019 10:45:25 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1551087925; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=5VDVzRtTdq1HCi3echiZWyul8dtalC0Wv7Xs0hXLp0E=; b=ihZGzOlxowqNIyzzvj073tz6/ROkm0sQYyoKBL6Geop3mbPUvKDEhigC5PT/icrGDqHIfM 7GM2ajZaRGPQLpNhmIpACzW31ERDqDChKAvpixDRrT/zqz95yBSRlghTNwoPPKURi252wm j7tk48DQJBHDQLBVcLWZQVSHiQuHPmY= Date: Mon, 25 Feb 2019 10:45:22 +0100 From: Borislav Petkov To: Pingfan Liu Cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Baoquan He , Will Deacon , Nicolas Pitre , Chao Fan , "Kirill A. Shutemov" , Ard Biesheuvel , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/boot/KASLR: skip the specified crashkernel reserved region Message-ID: <20190225094522.GC26145@zn.tnic> References: <1551081596-2856-1-git-send-email-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1551081596-2856-1-git-send-email-kernelfans@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 25, 2019 at 03:59:56PM +0800, Pingfan Liu wrote: > crashkernel=x@y option may fail to reserve the required memory region if > KASLR puts kernel into the region. To avoid this uncertainty, making KASLR > skip the required region. Lemme see if I understand this correctly: supplying crashkernel=X@Y influences where KASLR would put the randomized kernel. And it should be the other way around, IMHO. crashkernel= will have to "work" with KASLR to find a suitable range and if the reservation at Y fails, then we tell the user to try the more relaxed variant crashkernel=M. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.