From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752226AbeEPHIp convert rfc822-to-8bit (ORCPT ); Wed, 16 May 2018 03:08:45 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:58784 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751285AbeEPHIo (ORCPT ); Wed, 16 May 2018 03:08:44 -0400 Date: Wed, 16 May 2018 12:38:35 +0530 From: "Naveen N. Rao" Subject: Re: [RFC] powerpc/emulate_step: Fix kernel crash when VSX is not present To: mpe@ellerman.id.au, Ravi Bangoria , Michael Neuling Cc: anton@samba.org, cyrilbur@gmail.com, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, matthew.brown.dev@gmail.com, paulus@samba.org, sandipan@linux.vnet.ibm.com References: <20180516054021.5328-1-ravi.bangoria@linux.ibm.com> In-Reply-To: <20180516054021.5328-1-ravi.bangoria@linux.ibm.com> User-Agent: astroid/0.11.1 (https://github.com/astroidmail/astroid) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT X-TM-AS-GCONF: 00 x-cbid: 18051607-0008-0000-0000-000004F6F4E1 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18051607-0009-0000-0000-00001E8B604C Message-Id: <1526454049.ztv236j5bs.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-16_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805160072 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Adding Mikey] Ravi Bangoria wrote: > emulate_step() is not checking runtime VSX feature flag before > emulating an instruction. This can cause kernel oops when kernel > is compiled with CONFIG_VSX=y but running on machine where VSX is > not supported or disabled. Ex, while running emulate_step tests on > P6 machine: > > ... > emulate_step_test: lvx : PASS > emulate_step_test: stvx : PASS > Oops: Exception in kernel mode, sig: 4 [#1] > NIP [c000000000095c24] .load_vsrn+0x28/0x54 > LR [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0 > Call Trace: > [c0000000494c3770] [40fe240c7ae147ae] 0x40fe240c7ae147ae (unreliable) > [c0000000494c37f0] [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0 > [c0000000494c3900] [c000000000094f6c] .emulate_step+0x25c/0x5bc > [c0000000494c39b0] [c000000000ec90dc] .test_lxvd2x_stxvd2x+0x64/0x154 > [c0000000494c3b90] [c000000000ec9204] .test_emulate_step+0x38/0x4c > [c0000000494c3c00] [c00000000000de2c] .do_one_initcall+0x5c/0x2c0 > [c0000000494c3cd0] [c000000000eb4bf8] .kernel_init_freeable+0x314/0x4cc > [c0000000494c3db0] [c00000000000e1e4] .kernel_init+0x24/0x160 > [c0000000494c3e30] [c00000000000bc24] .ret_from_kernel_thread+0x58/0xb4 > > With fix: > ... > emulate_step_test: stvx : PASS > emulate_step_test: lxvd2x : FAIL > emulate_step_test: stxvd2x : FAIL Those tests should also be updated to skip testing these instructions if !CPU_FTR_VSX. > > Fixes: https://github.com/linuxppc/linux/issues/148 > > Reported-by: Michael Ellerman > Signed-off-by: Ravi Bangoria > --- > Note: VSX was first introduced on P6. But there are many VSX instructions > which were introduced in later versions. So ideally, analyse_instr() > should check for ISA version along with opcode. Yes, this patch should be useful for when VSX is not present. For specific instructions, we should add a cpu feature check. - Naveen