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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 A1339C3815B for ; Wed, 15 Apr 2020 20:36:47 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 67870206E9 for ; Wed, 15 Apr 2020 20:36:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="NZAONV3P" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 67870206E9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Subject:MIME-Version:Message-ID: In-Reply-To:Date:References:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=qf1qQrXErIFI+E6ew5YGPNe3V9MFHchK9UUlyNoPejs=; b=NZAONV3P/QJC/M 0iWxARHfVdPJpW2YnPhbJ+FBFbw6aJuh2Jcq4dFZUXGDX5jP+o46z6S+cQFwSh0x8prVzrSGb2Ofd nFj3/V0EP2bZ9jhax+OpTBhQzw5jc17Rsy8Y/FAYpH1SlIK1cFenhAQPRUR7D57o73OlR3Wvw3r9A VcPE8wBzqJKaO6GMuP5P5j+i1ucnKudaMqgiMefoW0C03CRHftRm/3bZOQCuBp7RnbmFIOYXYLumh uATZ2Rpk4BNnJaLfEvGazSrYEYrQiRyrDVaeEvnOXEaLqXU8DbLZ3q+ly8s3KuPKaPbbcU7fayqxa 839U4h4h7NB0RAGWOpyw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOom7-0000V3-02; Wed, 15 Apr 2020 20:36:47 +0000 Received: from out03.mta.xmission.com ([166.70.13.233]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOom4-0000Uc-Cm; Wed, 15 Apr 2020 20:36:45 +0000 Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jOom3-0008B3-3b; Wed, 15 Apr 2020 14:36:43 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jOom2-0003Rz-6x; Wed, 15 Apr 2020 14:36:42 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: James Morse References: <20200326180730.4754-1-james.morse@arm.com> <20200326180730.4754-2-james.morse@arm.com> Date: Wed, 15 Apr 2020 15:33:43 -0500 In-Reply-To: <20200326180730.4754-2-james.morse@arm.com> (James Morse's message of "Thu, 26 Mar 2020 18:07:28 +0000") Message-ID: <87d088h4k8.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1jOom2-0003Rz-6x; ; ; mid=<87d088h4k8.fsf@x220.int.ebiederm.org>; ; ; hst=in02.mta.xmission.com; ; ; ip=68.227.160.95; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX18VhUxMFCc7ESaZTTYHY/imM8juytRRcx0= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200415_133644_430352_F2969F64 X-CRM114-Status: GOOD ( 12.08 ) 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: Anshuman Khandual , Catalin Marinas , Bhupesh Sharma , kexec@lists.infradead.org, linux-mm@kvack.org, Andrew Morton , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org James Morse writes: > An image loaded for kexec is not stored in place, instead its segments > are scattered through memory, and are re-assembled when needed. In the > meantime, the target memory may have been removed. > > Because mm is not aware that this memory is still in use, it allows it > to be removed. > > Add a memory notifier to prevent the removal of memory regions that > overlap with a loaded kexec image segment. e.g., when triggered from the > Qemu console: > | kexec_core: memory region in use > | memory memory32: Offline failed. > > Signed-off-by: James Morse Given that we are talking about the destination pages for kexec not where the loaded kernel is currently stored the description is confusing. Beyond that I think it would be better to simply unload the loaded kernel at memory hotunplug time. Usually somewhere in the loaded image is a copy of the memory map at the time the kexec kernel was loaded. That will invalidate the memory map as well. All of this should be for a very brief window of a few seconds, as the loaded kexec image is quite short. So instead of failing in the notifier, if you could simply unload the loaded image in the notifier I think that would be simpler and more robust. While still preventing the loaded image from falling over when it starts executing. Eric _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel