Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759718AbcKDFbp (ORCPT ); Fri, 4 Nov 2016 01:31:45 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:34899 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757530AbcKDFbo (ORCPT ); Fri, 4 Nov 2016 01:31:44 -0400 Subject: Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE To: Andrew Donnellan , 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> <581B110F.9050805@linux.vnet.ibm.com> Cc: chris@distroguy.com, aneesh.kumar@linux.vnet.ibm.com, ast@kernel.org, linux-kernel@vger.kernel.org, oss@buserror.net, paul.gortmaker@windriver.com, duwe@lst.de, Anton Blanchard , lsorense@csclub.uwaterloo.ca, bauerman@linux.vnet.ibm.com, oohall@gmail.com, naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, paulus@samba.org, viro@zeniv.linux.org.uk, Ravi Bangoria From: Ravi Bangoria Date: Fri, 4 Nov 2016 11:01:30 +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: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16110405-0028-0000-0000-000005F2CE28 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006030; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000189; SDB=6.00776530; UDB=6.00373555; IPR=6.00553668; BA=6.00004855; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00013210; XFM=3.00000011; UTC=2016-11-04 05:31:41 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16110405-0029-0000-0000-0000308EF132 Message-Id: <581C1D32.50108@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-11-04_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-1611040104 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 988 Lines: 23 On Friday 04 November 2016 07:37 AM, Andrew Donnellan wrote: > On 03/11/16 21:27, Ravi Bangoria wrote: >> Yes, kernel-space hw-breakpoint feature is broken on LE without this. > > Is there any actual user-visible feature that depends on this, or is this solely for debugging and development purposes? > > It would of course be *nice* to have it in stable trees (particularly so we pick it up in distros) but I'm not convinced that enabling HW breakpoints on a platform where it has *never* worked qualifies as an "actual bug". > > (BTW many thanks for fixing this - I had a shot at it late last year but never quite got there!) Thanks Andrew, kprobe, uprobe, hw-breakpoint and xmon are the only user of emulate_step. Kprobe / uprobe single-steps instruction if they can't emulate it, so there is no problem with them. As I mention, hw-breakpoint is broken. However I'm not sure about xmon, I need to check that. So yes, there is no user-visible feature that depends on this. -Ravi