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 3vN0js1CCMzDqT6 for ; Tue, 14 Feb 2017 22:36:16 +1100 (AEDT) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1EBXbQO097549 for ; Tue, 14 Feb 2017 06:36:14 -0500 Received: from e38.co.us.ibm.com (e38.co.us.ibm.com [32.97.110.159]) by mx0b-001b2d01.pphosted.com with ESMTP id 28kwv4g3p1-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 14 Feb 2017 06:36:14 -0500 Received: from localhost by e38.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 14 Feb 2017 04:36:13 -0700 Subject: Re: [PATCH v3 1/2] powerpc: Emulation support for load/store instructions on LE To: Michael Ellerman References: <1487063803-10848-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com> <1487063803-10848-2-git-send-email-ravi.bangoria@linux.vnet.ibm.com> <87d1elm5uu.fsf@concordia.ellerman.id.au> Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, lsorense@csclub.uwaterloo.ca, oohall@gmail.com, naveen.n.rao@linux.vnet.ibm.com, ast@kernel.org, chris@distroguy.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, anton@samba.org, paul.gortmaker@windriver.com, bauerman@linux.vnet.ibm.com, viro@zeniv.linux.org.uk, christophe.leroy@c-s.fr, duwe@lst.de, oss@buserror.net, Ravi Bangoria From: Ravi Bangoria Date: Tue, 14 Feb 2017 17:05:57 +0530 MIME-Version: 1.0 In-Reply-To: <87d1elm5uu.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=windows-1252 Message-Id: <58A2EB9D.4080506@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Thanks Michael, On Tuesday 14 February 2017 03:50 PM, Michael Ellerman wrote: > Ravi Bangoria writes: > >> emulate_step() uses a number of underlying kernel functions that were >> initially not enabled for LE. This has been rectified since. > When exactly? ie. which commit. I found couple of commits: 6506b4718b ("powerpc: Fix Unaligned Loads and Stores") dbc2fbd7c2 ("powerpc: Fix Unaligned LE Floating Point Loads and Stores") There may be more. Patch2 is to test emulate_step() for basic load/store instructions and it seems to be working fine on LE. > > Should we backport this? ie. is it actually a bug people are hitting in > the real world much? Yes, we should backport this. kernel-space hw-breakpoint feature is broken on LE without this. This is on ppc64le: $ sudo cat /proc/kallsyms | grep pid_max c00000000116998c D pid_max $ sudo ./perf record -a --event=mem:0xc00000000116998c sleep 10 Before patch: It does not record any data and throws below warning. $ dmesg [ 817.895573] Unable to handle hardware breakpoint. Breakpoint at 0xc00000000116998c will be disabled. [ 817.895581] ------------[ cut here ]------------ [ 817.895588] WARNING: CPU: 24 PID: 2032 at arch/powerpc/kernel/hw_breakpoint.c:277 hw_breakpoint_handler+0x124/0x230 ... After patch: It records data properly. $ sudo ./perf report --stdio ... # Samples: 36 of event 'mem:0xc00000000116998c' # Event count (approx.): 36 # # Overhead Command Shared Object Symbol # ........ ............. ................ ............. # 63.89% kdumpctl [kernel.vmlinux] [k] alloc_pid 27.78% opal_errd [kernel.vmlinux] [k] alloc_pid 5.56% kworker/u97:4 [kernel.vmlinux] [k] alloc_pid 2.78% systemd [kernel.vmlinux] [k] alloc_pid > > cheers >