From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3t8h4N0cXCzDvRC for ; Thu, 3 Nov 2016 21:27:47 +1100 (AEDT) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uA3ANgvW010832 for ; Thu, 3 Nov 2016 06:27:42 -0400 Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) by mx0b-001b2d01.pphosted.com with ESMTP id 26g0rpcgkm-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 03 Nov 2016 06:27:41 -0400 Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 3 Nov 2016 06:27:40 -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 MIME-Version: 1.0 In-Reply-To: <8737j8opwb.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=windows-1252 Message-Id: <581B110F.9050805@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 >