From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933475AbdKGMGR (ORCPT ); Tue, 7 Nov 2017 07:06:17 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:51410 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754746AbdKGMGP (ORCPT ); Tue, 7 Nov 2017 07:06:15 -0500 Subject: Re: [PATCH v2] powerpc/kernel/sysfs: Export ldbar spr to sysfs To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, maddy@linux.vnet.ibm.com References: <1509466547-761-1-git-send-email-anju@linux.vnet.ibm.com> <87h8ue960z.fsf@concordia.ellerman.id.au> From: Anju T Sudhakar Date: Tue, 7 Nov 2017 17:36:08 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <87h8ue960z.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 17110712-0036-0000-0000-00000287EB1C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008025; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000239; SDB=6.00942405; UDB=6.00475382; IPR=6.00722693; BA=6.00005675; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017894; XFM=3.00000015; UTC=2017-11-07 12:06:11 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17110712-0037-0000-0000-0000424F3B81 Message-Id: <48d62ebb-73b9-86c6-b1f2-39ee1d3ae846@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-11-07_04:,, 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=8.0.1-1707230000 definitions=main-1711070168 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi mpe, On Wednesday 01 November 2017 06:20 AM, Michael Ellerman wrote: > Anju T Sudhakar writes: > >> Add ldbar spr to sysfs. The spr will hold thread level In-Memory Collection (IMC) >> counter configuration data. > This is missing any justification for why we would want to expose this, > and in particular why we would make it *writable*. > > cheers Thank you for reviewing the patch. LDBAR, holds the thread-level counter configuration. Exposing this will help us to understand  the current status of thread-level counters in the system. Primarily, Bit 0 of ldbar tells whether the counters are enabled or not. And bit 1  tells the mode (if 0-Accumulation Mode/if 1-Trace Mode). But regarding the permission, you are right. On a reassessment I think that the permission should be read only, because it is possible that we may write an incorrect value to the ldbar, that is wrong. So I will change the permission here. Thanks, Anju > >> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c >> index 4437c70..f8caee0 100644 >> --- a/arch/powerpc/kernel/sysfs.c >> +++ b/arch/powerpc/kernel/sysfs.c >> @@ -485,6 +485,7 @@ SYSFS_PMCSETUP(mmcra, SPRN_MMCRA); >> SYSFS_SPRSETUP(purr, SPRN_PURR); >> SYSFS_SPRSETUP(spurr, SPRN_SPURR); >> SYSFS_SPRSETUP(pir, SPRN_PIR); >> +SYSFS_SPRSETUP(ldbar, SPRN_LDBAR); >> >> /* >> Lets only enable read for phyp resources and >> @@ -492,6 +493,7 @@ SYSFS_SPRSETUP(pir, SPRN_PIR); >> Lets be conservative and default to pseries. >> */ >> static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra); >> +static DEVICE_ATTR(ldbar, 0600, show_ldbar, store_ldbar); >> static DEVICE_ATTR(spurr, 0400, show_spurr, NULL); >> static DEVICE_ATTR(purr, 0400, show_purr, store_purr); >> static DEVICE_ATTR(pir, 0400, show_pir, NULL); >> @@ -757,6 +759,9 @@ static int register_cpu_online(unsigned int cpu) >> device_create_file(s, &pmc_attrs[i]); >> >> #ifdef CONFIG_PPC64 >> + if (cpu_has_feature(CPU_FTR_ARCH_300)) >> + device_create_file(s, &dev_attr_ldbar); >> + >> if (cpu_has_feature(CPU_FTR_MMCRA)) >> device_create_file(s, &dev_attr_mmcra); >> >> @@ -842,6 +847,9 @@ static int unregister_cpu_online(unsigned int cpu) >> device_remove_file(s, &pmc_attrs[i]); >> >> #ifdef CONFIG_PPC64 >> + if (cpu_has_feature(CPU_FTR_ARCH_300)) >> + device_remove_file(s, &dev_attr_ldbar); >> + >> if (cpu_has_feature(CPU_FTR_MMCRA)) >> device_remove_file(s, &dev_attr_mmcra); >> >> -- >> 2.7.4