Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756665AbcKCK1n (ORCPT ); Thu, 3 Nov 2016 06:27:43 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:53087 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756365AbcKCK1m (ORCPT ); Thu, 3 Nov 2016 06:27:42 -0400 Subject: Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE To: Michael Ellerman References: <1478076783-2872-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com> <1478076783-2872-2-git-send-email-ravi.bangoria@linux.vnet.ibm.com> <20161103080412.68240cda@kryten> <581ACDF2.1010409@linux.vnet.ibm.com> <8737j8opwb.fsf@concordia.ellerman.id.au> Cc: Anton Blanchard , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, duwe@lst.de, ast@kernel.org, viro@zeniv.linux.org.uk, chris@distroguy.com, oss@buserror.net, paul.gortmaker@windriver.com, oohall@gmail.com, aneesh.kumar@linux.vnet.ibm.com, lsorense@csclub.uwaterloo.ca, bauerman@linux.vnet.ibm.com, paulus@samba.org, naveen.n.rao@linux.vnet.ibm.com, Ravi Bangoria From: Ravi Bangoria Date: Thu, 3 Nov 2016 15:57:27 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <8737j8opwb.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16110310-0056-0000-0000-000001D102F3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006025; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000189; SDB=6.00776177; UDB=6.00373328; IPR=6.00553326; BA=6.00004854; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00013199; XFM=3.00000011; UTC=2016-11-03 10:27:39 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16110310-0057-0000-0000-00000604206E Message-Id: <581B110F.9050805@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-11-03_02:,, 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=8.0.1-1609300000 definitions=main-1611030195 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1185 Lines: 35 On Thursday 03 November 2016 03:18 PM, Michael Ellerman wrote: > Ravi Bangoria writes: > >> On Thursday 03 November 2016 02:34 AM, Anton Blanchard wrote: >>> Hi Ravi, >>> >>>> emulate_step() uses a number of underlying kernel functions that were >>>> initially not enabled for LE. This has been rectified since. So, fix >>>> emulate_step() for LE for the corresponding instructions. >>> Thanks. Should this be queued up for stable? >> Thanks Anton. Yes, this should go in stable. > It's fairly big for stable. Does it fix an actual bug? If so what, and > how bad is it, what's the user impact. Hi Michael, Yes, kernel-space hw-breakpoint feature is broken on LE without this. Actually, there is no specific commit that introduced this. Back in 2010, Paul Mackerras has added emulation support for load/store instructions for BE. hw-breakpoint was also develpoed by K.Prasad in the same timeframe. Kernel-space hw-breakpoint emulates causative instruction before notifying to user. As emulate_step is never enabled for LE, kernel- space hw-breakpoint is always broken on LE. -Ravi > Can you also pinpoint which commit it "fixes"? > > cheers >