Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751377AbdISKE4 (ORCPT ); Tue, 19 Sep 2017 06:04:56 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45234 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750952AbdISKEy (ORCPT ); Tue, 19 Sep 2017 06:04:54 -0400 Subject: Re: [PATCH] powerpc/sysrq: Fix oops whem ppmu is not registered To: Michael Ellerman , Ravi Bangoria , linuxppc-dev@lists.ozlabs.org Cc: benh@kernel.crashing.org, paulus@samba.org, tglx@linutronix.de, mingo@kernel.org, kan.liang@intel.com, linux-kernel@vger.kernel.org References: <1505801826-12396-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com> <87wp4vknxq.fsf@concordia.ellerman.id.au> From: Madhavan Srinivasan Date: Tue, 19 Sep 2017 15:34:40 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <87wp4vknxq.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-MML: disable x-cbid: 17091910-0008-0000-0000-00000158476E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17091910-0009-0000-0000-0000098D8F98 Message-Id: <6d061729-f2a2-ed05-2008-46c78ef4bd6f@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-09-19_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1709190143 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1168 Lines: 41 On Tuesday 19 September 2017 03:30 PM, Michael Ellerman wrote: > Ravi Bangoria writes: > >> Kernel crashes if power pmu is not registered and user tries to dump >> regs with 'echo p > /proc/sysrq-trigger'. Sample log: >> >> Unable to handle kernel paging request for data at address 0x00000008 >> Faulting instruction address: 0xc0000000000d52f0 >> >> NIP [c0000000000d52f0] perf_event_print_debug+0x10/0x230 >> LR [c00000000058a938] sysrq_handle_showregs+0x38/0x50 >> Call Trace: >> printk+0x38/0x4c (unreliable) >> __handle_sysrq+0xe4/0x270 >> write_sysrq_trigger+0x64/0x80 >> proc_reg_write+0x80/0xd0 >> __vfs_write+0x40/0x200 >> vfs_write+0xc8/0x240 >> SyS_write+0x60/0x110 >> system_call+0x58/0x6c > Thanks. > > I added: > > Fixes: 5f6d0380c640 ("powerpc/perf: Define perf_event_print_debug() to print PMU register values") > > But I don't think I'll Cc stable, I can't think why we'd ever *not* have > a ppmu registered. How did you hit it? mpe, We hit this in a compact mode setup where the distro kernel did not have the pmu support for the base pvr. Maddy > cheers >