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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 ECB70C43387 for ; Fri, 11 Jan 2019 15:47:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C005E20700 for ; Fri, 11 Jan 2019 15:47:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732407AbfAKPrz (ORCPT ); Fri, 11 Jan 2019 10:47:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50680 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731339AbfAKPrz (ORCPT ); Fri, 11 Jan 2019 10:47:55 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DCB4FC05D410; Fri, 11 Jan 2019 15:47:54 +0000 (UTC) Received: from gondolin (ovpn-117-121.ams2.redhat.com [10.36.117.121]) by smtp.corp.redhat.com (Postfix) with ESMTP id 85EF31E7; Fri, 11 Jan 2019 15:47:49 +0000 (UTC) Date: Fri, 11 Jan 2019 16:47:46 +0100 From: Cornelia Huck To: David Hildenbrand Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Randy Dunlap , Mike Rapoport , Vasily Gorbik , Andrew Morton , Heiko Carstens , Martin Schwidefsky Subject: Re: [PATCH v1] s390/smp: Fix calling smp_call_ipl_cpu() from ipl CPU Message-ID: <20190111164746.015e16da.cohuck@redhat.com> In-Reply-To: <20190111141822.17262-1-david@redhat.com> References: <20190111141822.17262-1-david@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Fri, 11 Jan 2019 15:47:55 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Jan 2019 15:18:22 +0100 David Hildenbrand wrote: > When calling smp_call_ipl_cpu() from the IPL CPU, we will try to read > from pcpu_devices->lowcore. However, due to prefixing, that will result > in reading from absolute address 0 on that CPU. We have to go via the > actual lowcore instead. > > This means that right now, we will read lc->nodat_stack == 0 and > therfore work on a very wrong stack. > > This BUG essentially broke rebooting under QEMU TCG (which will report > a low address protection exception). And checking under KVM, it is > also broken under KVM. With 1 VCPU it can be easily triggered. > > :/# echo 1 > /proc/sys/kernel/sysrq > :/# echo b > /proc/sysrq-trigger > [ 28.476745] sysrq: SysRq : Resetting > [ 28.476793] Kernel stack overflow. > [ 28.476817] CPU: 0 PID: 424 Comm: sh Not tainted 5.0.0-rc1+ #13 > [ 28.476820] Hardware name: IBM 2964 NE1 716 (KVM/Linux) > [ 28.476826] Krnl PSW : 0400c00180000000 0000000000115c0c (pcpu_delegate+0x12c/0x140) > [ 28.476861] R:0 T:1 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 > [ 28.476863] Krnl GPRS: ffffffffffffffff 0000000000000000 000000000010dff8 0000000000000000 > [ 28.476864] 0000000000000000 0000000000000000 0000000000ab7090 000003e0006efbf0 > [ 28.476864] 000000000010dff8 0000000000000000 0000000000000000 0000000000000000 > [ 28.476865] 000000007fffc000 0000000000730408 000003e0006efc58 0000000000000000 > [ 28.476887] Krnl Code: 0000000000115bfe: 4170f000 la %r7,0(%r15) > [ 28.476887] 0000000000115c02: 41f0a000 la %r15,0(%r10) > [ 28.476887] #0000000000115c06: e370f0980024 stg %r7,152(%r15) > [ 28.476887] >0000000000115c0c: c0e5fffff86e brasl %r14,114ce8 > [ 28.476887] 0000000000115c12: 41f07000 la %r15,0(%r7) > [ 28.476887] 0000000000115c16: a7f4ffa8 brc 15,115b66 > [ 28.476887] 0000000000115c1a: 0707 bcr 0,%r7 > [ 28.476887] 0000000000115c1c: 0707 bcr 0,%r7 > [ 28.476901] Call Trace: > [ 28.476902] Last Breaking-Event-Address: > [ 28.476920] [<0000000000a01c4a>] arch_call_rest_init+0x22/0x80 > [ 28.476927] Kernel panic - not syncing: Corrupt kernel stack, can't continue. > [ 28.476930] CPU: 0 PID: 424 Comm: sh Not tainted 5.0.0-rc1+ #13 > [ 28.476932] Hardware name: IBM 2964 NE1 716 (KVM/Linux) > [ 28.476932] Call Trace: > > Reported-by: Cornelia Huck > Signed-off-by: David Hildenbrand > --- > arch/s390/kernel/smp.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) I can confirm that this patch fixes rebooting for me, both under QEMU/TCG and under QEMU/KVM (1 vcpu). Tested-by: Cornelia Huck