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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 92B39C43331 for ; Tue, 31 Mar 2020 03:38:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5470E206EB for ; Tue, 31 Mar 2020 03:38:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iuZDaphc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5470E206EB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E4A6D6B0032; Mon, 30 Mar 2020 23:38:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DFAED6B0037; Mon, 30 Mar 2020 23:38:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D0FD78E0001; Mon, 30 Mar 2020 23:38:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0171.hostedemail.com [216.40.44.171]) by kanga.kvack.org (Postfix) with ESMTP id B64226B0032 for ; Mon, 30 Mar 2020 23:38:45 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 7CEB63A97 for ; Tue, 31 Mar 2020 03:38:45 +0000 (UTC) X-FDA: 76654250610.06.fifth84_869d73433a005 X-HE-Tag: fifth84_869d73433a005 X-Filterd-Recvd-Size: 5135 Received: from us-smtp-delivery-74.mimecast.com (us-smtp-delivery-74.mimecast.com [216.205.24.74]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Tue, 31 Mar 2020 03:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585625924; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Inos4B5b9Pernn1AkDhMDrwPjBNHDVB82TQHk4Lb/8A=; b=iuZDaphcOA5MHmcljbEWoi4TjBsfjw0EH3VE6EVi1D4usDAPhfxtcnIP1wFrMCj//evwE/ I0v0B676JHEmcji94cn9bYZ95f8ifTx3A7Tv2i/cKW9ZK2PJAMAxDRvxCXMaW0ddJkkEfY nlytDIYYRbMQrJeQZThqK+IyXK/gWhg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-419-sNsFbYK-O0GHoJvQelgsiw-1; Mon, 30 Mar 2020 23:38:38 -0400 X-MC-Unique: sNsFbYK-O0GHoJvQelgsiw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 65558107ACC4; Tue, 31 Mar 2020 03:38:36 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-12-247.pek2.redhat.com [10.72.12.247]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 487A750BEE; Tue, 31 Mar 2020 03:38:31 +0000 (UTC) Date: Tue, 31 Mar 2020 11:38:27 +0800 From: Dave Young To: James Morse Cc: kexec@lists.infradead.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Anshuman Khandual , Catalin Marinas , Bhupesh Sharma , Eric Biederman , Andrew Morton , Will Deacon Subject: Re: [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use Message-ID: <20200331033827.GA83248@dhcp-128-65.nay.redhat.com> References: <20200326180730.4754-1-james.morse@arm.com> MIME-Version: 1.0 In-Reply-To: <20200326180730.4754-1-james.morse@arm.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi James, On 03/26/20 at 06:07pm, James Morse wrote: > Hello! >=20 > arm64 recently queued support for memory hotremove, which led to some > new corner cases for kexec. >=20 > If the kexec segments are loaded for a removable region, that region may > be removed before kexec actually occurs. This causes the first kernel to > lockup when applying the relocations. (I've triggered this on x86 too). Does a kexec reload work for your case? If yes then I would suggest to do it in userspace, for example have a udev rule to reload kexec if needed. Actually we have a rule to restart kdump loading, but not for kexec, it sounds also need a service to load kexec, and an udev rule to reload for memory hotplug. >=20 > The first patch adds a memory notifier for kexec so that it can refuse > to allow in-use regions to be taken offline. >=20 >=20 > This doesn't solve the problem for arm64, where the new kernel must > initially rely on the data structures from the first boot to describe > memory. These don't describe hotpluggable memory. > If kexec places the kernel in one of these regions, it must also provide > a DT that describes the region in which the kernel was mapped as memory. > (and somehow ensure its always present in the future...) >=20 > To prevent this from happening accidentally with unaware user-space, > patches two and three allow arm64 to give these regions a different > name. >=20 > This is a change in behaviour for arm64 as memory hotadd and hotremove > were added separately. >=20 >=20 > I haven't tried kdump. > Unaware kdump from user-space probably won't describe the hotplug > regions if the name is different, which saves us from problems if > the memory is no longer present at kdump time, but means the vmcore > is incomplete. >=20 >=20 > These patches are based on arm64's for-next/core branch, but can all > be merged independently. >=20 > Thanks, >=20 > James Morse (3): > kexec: Prevent removal of memory in use by a loaded kexec image > mm/memory_hotplug: Allow arch override of non boot memory resource > names > arm64: memory: Give hotplug memory a different resource name >=20 > arch/arm64/include/asm/memory.h | 11 +++++++ > kernel/kexec_core.c | 56 +++++++++++++++++++++++++++++++++ > mm/memory_hotplug.c | 6 +++- > 3 files changed, 72 insertions(+), 1 deletion(-) >=20 > --=20 > 2.25.1 >=20 >=20 > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec >=20 Thanks Dave