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=-2.5 required=3.0 tests=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 831DCC0044C for ; Wed, 7 Nov 2018 09:35:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 563832081D for ; Wed, 7 Nov 2018 09:35:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 563832081D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728528AbeKGTFU (ORCPT ); Wed, 7 Nov 2018 14:05:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43494 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726097AbeKGTFU (ORCPT ); Wed, 7 Nov 2018 14:05:20 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 32489A4055; Wed, 7 Nov 2018 09:35:48 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-12-74.pek2.redhat.com [10.72.12.74]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4FC031711B; Wed, 7 Nov 2018 09:35:44 +0000 (UTC) Date: Wed, 7 Nov 2018 17:35:40 +0800 From: Dave Young To: lijiang Cc: Baoquan He , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, akpm@linux-foundation.org Subject: Re: [PATCH 2/2 v5] x86/kexec_file: add reserved e820 ranges to kdump kernel e820 table Message-ID: <20181107093540.GA8521@dhcp-128-65.nay.redhat.com> References: <20181107050019.6663-1-lijiang@redhat.com> <20181107050019.6663-3-lijiang@redhat.com> <20181107052345.GQ27491@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.5 (2018-04-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 07 Nov 2018 09:35:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/07/18 at 05:10pm, lijiang wrote: > 在 2018年11月07日 13:23, Baoquan He 写道: > > On 11/07/18 at 01:00pm, Lianbo Jiang wrote: > >> E820 reserved ranges is useful in kdump kernel, it has been added in > >> kexec-tools code. > >> > >> One reason is PCI mmconf (extended mode) requires reserved region otherwise > >> it falls back to legacy mode, and also outputs the following kernel log. > > > > OK, it falls back to legacy mode, and also output kernel log, except of > > these, does it crash kernel? kdump kernel hang? Can we leave it if it > > only ouptut kernel log? > > > >> > >> Example: > >> ...... > >> [ 19.798354] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000) > >> [ 19.800653] [Firmware Info]: PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] not reserved in ACPI motherboard resources > >> [ 19.800995] PCI: not using MMCONFIG > >> ...... > >> > >> The correct kernel log is like this: > >> ...... > >> [ 0.082649] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000) > >> [ 0.083610] PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] reserved in E820 > >> ...... > >> > >> Furthermore, when AMD SME kdump support, it needs to map dmi table area > >> as decrypted. For normal boot, these ranges sit in e820 reserved ranges, > >> thus the early ioremap code naturally map them as decrypted. If it also > >> has same e820 reserve setup in kdump kernel then it will just work like > >> normal kernel. > > > > Why do we care? If don't fix, what's happening? > > > > Lianbo, for a bug fix, please describe the problems. Then give out the > > analysis about root cause. > > > > Thanks for your comment in detail. > > In fact, these patches are really simple. As the subject mentioned, this patch > [PATCH 2/2] adds the reserved e820 ranges to kdump kernel e820 table, and the > first patch [PATCH 1/2] helps to exactly add the e820(E820_TYPE_RESERVED) type > to kdump kernel e820 table, that is to say, it will filter out some unnecessary > type(E820_TYPE_RAM/E820_TYPE_UNUSABLE/E820_TYPE_RESERVED_KERN). > > At present, when we use the kexec to load the kernel image and initramfs(for > example: kexec -s -p xxxx), the latest kernel does not pass the e820 reserved > ranges to the second kernel, which might produce two problems: > > The first one is the MMCONFIG issue, although which does not make the system > crash or hang, this issue is still a potential risk, because my test can't > cover all cases due to resource constraints(Machine), and i'm not sure what > it will happen on other machine. If a device is plugged in pci domain 1 then this device can not be recognized in kdump kernel in your case. For example if one want to dump to a network target, but the net card can not be recognized then vmcore can not be saved successfully Thanks Dave