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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 0CB79C4740A for ; Mon, 7 Oct 2019 07:09:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC03122473 for ; Mon, 7 Oct 2019 07:09:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727383AbfJGHJE (ORCPT ); Mon, 7 Oct 2019 03:09:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36290 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727028AbfJGHJC (ORCPT ); Mon, 7 Oct 2019 03:09:02 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id A678410C0937; Mon, 7 Oct 2019 07:09:01 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-12-87.pek2.redhat.com [10.72.12.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id BF8C4600C1; Mon, 7 Oct 2019 07:08:48 +0000 (UTC) From: Lianbo Jiang To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, bhe@redhat.com, dyoung@redhat.com, jgross@suse.com, dhowells@redhat.com, Thomas.Lendacky@amd.com, ebiederm@xmission.com, vgoyal@redhat.com, kexec@lists.infradead.org Subject: [PATCH v2] x86/kdump: Fix 'kmem -s' reported an invalid freepointer when SME was active Date: Mon, 7 Oct 2019 15:08:44 +0800 Message-Id: <20191007070844.15935-1-lijiang@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.66]); Mon, 07 Oct 2019 07:09:01 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204793 Kdump kernel will reuse the first 640k region because of some reasons, for example: the trampline and conventional PC system BIOS region may require to allocate memory in this area. Obviously, kdump kernel will also overwrite the first 640k region, therefore, kernel has to copy the contents of the first 640k area to a backup area, which is done in purgatory(), because vmcore may need the old memory. When vmcore is dumped, kdump kernel will read the old memory from the backup area of the first 640k area. Basically, the main reason should be clear, kernel does not correctly handle the first 640k region when SME is active, which causes that kernel does not properly copy these old memory to the backup area in purgatory(). Therefore, kdump kernel reads out the incorrect contents from the backup area when dumping vmcore. Finally, the phenomenon is as follow: [root linux]$ crash vmlinux /var/crash/127.0.0.1-2019-09-19-08\:31\:27/vmcore WARNING: kernel relocated [240MB]: patching 97110 gdb minimal_symbol values KERNEL: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmlinux DUMPFILE: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmcore [PARTIAL DUMP] CPUS: 128 DATE: Thu Sep 19 08:31:18 2019 UPTIME: 00:01:21 LOAD AVERAGE: 0.16, 0.07, 0.02 TASKS: 1343 NODENAME: amd-ethanol RELEASE: 5.3.0-rc7+ VERSION: #4 SMP Thu Sep 19 08:14:00 EDT 2019 MACHINE: x86_64 (2195 Mhz) MEMORY: 127.9 GB PANIC: "Kernel panic - not syncing: sysrq triggered crash" PID: 9789 COMMAND: "bash" TASK: "ffff89711894ae80 [THREAD_INFO: ffff89711894ae80]" CPU: 83 STATE: TASK_RUNNING (PANIC) crash> kmem -s|grep -i invalid kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 crash> BTW: I also tried to fix the above problem in purgatory(), but there are too many restricts in purgatory() context, for example: i can't allocate new memory to create the identity mapping page table for SME situation. Currently, there are two places where the first 640k area is needed, the first one is in the find_trampoline_placement(), another one is in the reserve_real_mode(), and their content doesn't matter. To avoid the above error, lets occupy the remain memory of the first 640k region (expect for the trampoline and real mode) so that the allocated memory does not fall into the first 640k area when SME is active, which makes us not to worry about whether kernel can correctly copy the contents of the first 640k area to a backup region in the purgatory(). Signed-off-by: Lianbo Jiang --- Changes since v1: 1. Improve patch log 2. Change the checking condition from sme_active() to sme_active() && strstr(boot_command_line, "crashkernel=") arch/x86/kernel/setup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 77ea96b794bd..bdb1a02a84fd 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1148,6 +1148,9 @@ void __init setup_arch(char **cmdline_p) reserve_real_mode(); + if (sme_active() && strstr(boot_command_line, "crashkernel=")) + memblock_reserve(0, 640*1024); + trim_platform_memory_ranges(); trim_low_memory_range(); -- 2.17.1