Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <eb23ad55-a46c-4ed7-d2b0-0dcf7d536f89@oracle.com>
Date:   Mon, 14 Aug 2023 15:43:48 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.14.0
Subject: Re: [PATCH v5 2/6] perf arm64: Allow version comparisons of CPU IDs
To:     James Clark <james.clark@arm.com>,
        linux-perf-users@vger.kernel.org, irogers@google.com,
        renyu.zj@linux.alibaba.com
Cc:     Will Deacon <will@kernel.org>, Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Nick Forrington <nick.forrington@arm.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Eduard Zingerman <eddyz87@gmail.com>,
        Sohom Datta <sohomdatta1@gmail.com>,
        Rob Herring <robh@kernel.org>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org
References: <20230811144017.491628-1-james.clark@arm.com>
 <20230811144017.491628-3-james.clark@arm.com>
 <47a32410-d9ca-627b-e8a3-f64d4a1ea95f@oracle.com>
 <4c6a4729-8331-5c47-a81e-f92915e2e848@arm.com>
Content-Language: en-US
From:   John Garry <john.g.garry@oracle.com>
Organization: Oracle Corporation
In-Reply-To: <4c6a4729-8331-5c47-a81e-f92915e2e848@arm.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?NDBYT24vOFhuc1hvTXAxU0RUNTIvUUc2MzRMaWU0L3NrU0RYVWN2Y2kzVk9t?=
 =?utf-8?B?MisxSFdWS2VvK0p6UlJIRFozNTFRUkF4MGc2M3crNXlvMUdRa2FyMWR0MkZK?=
 =?utf-8?B?ZXlBSEFTRkV0LzVEMEFEV25QeDVHbDVZcWxNQ1ZwWWI5Q2tFdTRPRlNYNVdO?=
 =?utf-8?B?TFNiblpOcHhobTk1QUk3dXBhOWdIcnJ1UVVoSE9lL0hyNUU3SmsvWjdhQ0RW?=
 =?utf-8?B?VDFvTjlWZHRVOGZNYmZ0MS9TTGhSLzV0Z3JwR09ZK3FVNTFQdmM0YTM1MEQ4?=
 =?utf-8?B?bFRkck1OcDZnbDdmUzdlOGxTS3hzZy96eXhzUCt3QTdONUNsNHhWZVlWaUQw?=
 =?utf-8?B?Y0sxcWpYcS9NNVNGb1NIeGlqVUNEb2VSaStUblJFN09MUE5jWTNSbkRuTHhO?=
 =?utf-8?B?QXpLYjdUR256V2FWaHBpcUtQMm1pT200UlR5NUhFS2FvVlI5MWRaTWZMUFo5?=
 =?utf-8?B?cEg4dkxSNTBVcVArOU5ZUDBJRCtmNXVsaUtNM3NmaTJuTmJTZlM1SStMWE0v?=
 =?utf-8?B?cVhNTlpIVWQ3WlJCaVlvM1JVTS96TUptM3Q4ME5LeTJGU3JPdEZCNW1YNW9L?=
 =?utf-8?B?clBMa0JYUDQ4K1k2MDU5enBXZDQxV0xkaHJqNjhaREE4bmJEdGsvbTZoN1NB?=
 =?utf-8?B?ZWY5bktVbXJVQTdFMGVEaFJHcjFUWCsvT0VLa1dKOXUxUzBiZGNwYTk3OEcr?=
 =?utf-8?B?Q21kVHNKOHRUbE0rdlQrT2hPWWFBVTUwWHJtZmFIK0xRODZGOE50SmZNeG1M?=
 =?utf-8?B?LzhuSktSOWQ1KzNWakpJOTh2RnhvZlRVZnk1YnBWUlgxUkljWSs5SmZBS1Vm?=
 =?utf-8?B?YXBEWGNIL1o2VnZ0d3RPV2ZOU3dhQjBxTCtXTXZETFVlc1ZoUm9TaU9KcmJX?=
 =?utf-8?B?enhzNnlFdFcwUERINktHb3ZseGR2L0F2djBxRldjZ25qeXpraWRzOXk4bkl4?=
 =?utf-8?B?L2VxUGFZVWFKc0Y4K0ZYcFM3MVdIRmdrdnFIdmVWcHFFSG9XVmxaWWZCY2M1?=
 =?utf-8?B?ZFdMSkd3QWpVaWk2YlVJa29ycHlkTEFuMi9JMDQ3emxpVUZ4a3RUWllYUTRG?=
 =?utf-8?B?Y2FNajlSaTJGWVg3UktnVWFzSnpyUjg4VkNXZk5SdzhqRFM0Tk9qSFIvVXpN?=
 =?utf-8?B?NVp3aFFPSkNvN09oQXR4NDNDaEdTL04vRWJZTXYvREkwSnFwWEpySXNob2d4?=
 =?utf-8?B?Z1F0cm1JVWJzdDZSMEdkOFBQNW0rYVl1SzNSZllBN0xzVzBHTVVJY0xYWEpa?=
 =?utf-8?B?cnhSeEJDM1F3VUxlSEYzYWhac1d5b3lKK2tEbWtpYkEvM0RlTjJjNjg5aHlM?=
 =?utf-8?B?UnRRbFl4VVUxZkJidUhmdUp6L1BBL05VYUhYQkYrbms3SEdVSWZsdHQxUk93?=
 =?utf-8?B?dmJYa1hSM1lDckg0aHp0Tzk1eWVSdjdiU01QN3BKRGI1M2pZbUhQMXUraGd1?=
 =?utf-8?B?MW1WUktvdHpkblhrQkNTcHFmUnR6VWNNRDVNNm5kelBzSW94MFBBYTBpa2Fq?=
 =?utf-8?B?RWFpTGFvV1VGVzh0dGdOWTljTDJOdVFjZEROcDh3dE1uN3dTOXNIQkw5UUtE?=
 =?utf-8?B?cDltVmNkWEk0RGxHREY1ZkZyWGRHQjRrd05wUHVXdVgxNDNHOTR6L2s5ZUE4?=
 =?utf-8?B?MWJpZGlxQm81eWRheWxVRTlGc1dEV01jOTJva2tJYWdRWUF4M2NtdExkVkJn?=
 =?utf-8?B?OEt4a0dKaTZRSU5uaC9HdXBCVjljOVdZRnhJWmdDc2dzNExNNUR0OUhldG1p?=
 =?utf-8?B?MG81RHJuT1VCMTduUXBSeUJYRTFUYnpJdTFVZGpYSkZhRHF5d0xkWDhHa2tM?=
 =?utf-8?B?QTVDNWV0bDJ2VlRqZGxaQTdTSXhNTXZQTjROb0xJK3o2NGpCWHRYY29zekpQ?=
 =?utf-8?B?NmYyYTdIUVRTRXZzMC9FZEJWdXE0Q1UwMmttYXp2MXpRTnFhVHBteU1TMGZp?=
 =?utf-8?B?VmpsdHJiaEtxZUU3T0ViTGFEMTZPZlZLTW5zSkZ4ekwrNjcvUDNEVGdGTXVB?=
 =?utf-8?B?T0tuYkVPcHRXWTNpdXBpa25Na0Z2VXpGZDNJTjFYQkpuK1pCKzF1MWVYYkhB?=
 =?utf-8?B?TjI0ejdNaW9zOXZSdzlub1drbERxUnhSa29EbHJsZzJaTkJHZ3VXa2N5V2da?=
 =?utf-8?B?V2VqSXdOVGJweUZoOVlNRy9JcUtpNUFMSjd3dWVaWENPWTVpZGlBU2NWb3FJ?=
 =?utf-8?B?T1E9PQ==?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?utf-8?B?bnhvVVlPR1dyWUNXbDh1QTV6b2FPQU0zSEx5dnFXeTcrZzR1c3AvT1dRTHd3?=
 =?utf-8?B?QXJHelBnbmxTYVhzWHhBNEtMdGRSdlczOVJVTWxEODlKRmc0aWR0SDMrTits?=
 =?utf-8?B?VWtkdnJSaWdHMi9zaDVZSU45K21HcVEreHF0UUdGZkEwMjRHVm1RZVYva043?=
 =?utf-8?B?NHNnOTFnYXUzanNLS0NvRks3YmlmZWVwM01FTDU4Z2twbUtQaHFyTTRLam1X?=
 =?utf-8?B?MVczc1J0c05aeWJiZlh5bU5RZU5nWXhQQndqNXhIY2tFdUZMYTRVN1grR3RJ?=
 =?utf-8?B?aDBwZDRJR1dLa0o5SG5wT1VQMHcxc2toVWNOM1hSM2dueTVWNERPem9BZGww?=
 =?utf-8?B?Nkt2S0lDcHJGc1M4NlBveG4ybU8wNVFxNFFMeStCOXJsSk1aS0NTTk9lZ1Fi?=
 =?utf-8?B?T3gxRmthWUlTTW1zSTdzSVowTmZiWjIrUWFHS0tTMUdhQW10QkVhVzBqZnda?=
 =?utf-8?B?UzBMcmRCeEVPTEZ2MXRNT29reVBjVmh6WWJJWVpGamdaVmU3ZXpjMnMrOWdR?=
 =?utf-8?B?TEQyOTFiWllsVU9MdWlZQ0Z0TW80bUZJRTcrK3cyQmVYam8yYmd2VDZuY1Jx?=
 =?utf-8?B?S0FldGNkeUxnRnJNVkpDVEV5anIreTU1TWJ5bUF2UkkranE4aHNaT3FmOFVs?=
 =?utf-8?B?RHUzKzc4RGhMdno0djNsSnBXTFZ2cHZxUTZFSXRieUVjWGw3SkpVU0s0aU8v?=
 =?utf-8?B?RFdPZDBFMEVldjRJOU9JSmhNY2M3KzVFT3JLc2p6K25mbmhxUzdza09UV0ZF?=
 =?utf-8?B?TmhRYmlpR0ppS0owL2xRZ0FHYkh3eGdyc1pucUNqblhxdjNMY2dKbkhSeFhv?=
 =?utf-8?B?LzAyWVVLNmdldDVTSmp5dG5MbUlweGErK09LRndISTRJQlk1eUVRMGlCQU5k?=
 =?utf-8?B?UktoM0ZxOUJEZ05wRTlsSDl0NFlIbW5CdEFiNHliWHNKYlMrN3daZzcxeStP?=
 =?utf-8?B?QTFhWWhTMHN4d3dRWjBOajVNaytCUzIxeEFIaHZVWVN4QjZwbzNOWG1HcERl?=
 =?utf-8?B?R0ZXN25JcUJaZ04rS0xVZGtTUDZrdEw3NXY1Ymx3M1B5Slc3bk1rUDdhb1Fl?=
 =?utf-8?B?bk1sSUZOc1Vta3RQdDN5UWlUUG1zc2xaalJoamMvSnVoNW9Ta2ZTUTNrQlRj?=
 =?utf-8?B?TzB1OTJHNDJwSWVqWFhsVkt5R1NPQmNNcUllcTQzTWhOd2M1M2lSazR6eTUy?=
 =?utf-8?B?NEFoYlNWcnA3SmhSbTdSVURQOFEyMkF5WTd5WXcxclBtRlZtQ1ltMXppYTVL?=
 =?utf-8?B?VkRseDgwd2VuczVyWGlyQkU1TnBLbUxQc00xSzFjSnNQbHR4QXhHV2NrRTQy?=
 =?utf-8?B?aE9NY0NuakRuT0hCZkMrWFZwZjNCcklKVzlVbXFqTGFhb29vVzNZR3NGUEJ0?=
 =?utf-8?B?clFqamF1dEJCTFRTcjFXR2VaY2xSNEZZa1hEMHlhTmpQMGhabHVzbmYzc2Rj?=
 =?utf-8?B?RjdMeUw4UkozS05ZdlVHRnc4elJDRmtjbGFZRHZNRi9nejFKcHY1ODBnWWdY?=
 =?utf-8?B?b29IQ3hCQmU4cU1FamZzR3RNS0dsMFhaWEZucmlab0MvYktnTTBPdDNPUmxx?=
 =?utf-8?B?dzlCVkI3RFBrSmFTbENRVFFqd2lydGU4YW10MTJHc2xFQlhET1FKUjh1aWM0?=
 =?utf-8?B?ZWh4QlpkK05iZWJmRXRTbmRVRUpzMUE9PQ==?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: b7524673-d63f-404f-dbe0-08db9cd4e269
X-MS-Exchange-CrossTenant-AuthSource: DM6PR10MB4313.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Aug 2023 14:43:55.1693
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: WhJvCI0CO6bKzQ7Jp11Kh2beCywi1+ZpleTIrr1acPl4OKCnjlQQRexZtZe0AOL+ow/ZcgiZ5iqq8ZXiFVBXXA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR10MB6294
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26
 definitions=2023-08-14_11,2023-08-10_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 phishscore=0 mlxscore=0
 spamscore=0 malwarescore=0 mlxlogscore=999 suspectscore=0 adultscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2306200000
 definitions=main-2308140137
X-Proofpoint-GUID: CDxysIntV4yRjHyPCLzm-qvKW7pTavEr
X-Proofpoint-ORIG-GUID: CDxysIntV4yRjHyPCLzm-qvKW7pTavEr
X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE
        autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 14/08/2023 15:15, James Clark wrote:
> 
> On 14/08/2023 14:07, John Garry wrote:
>> On 11/08/2023 15:39, James Clark wrote:
>>> Currently variant and revision fields are masked out of the MIDR so
>>> it's not possible to compare different versions of the same CPU.
>>> In a later commit a workaround will be removed just for N2 r0p3, so
>>> enable comparisons on version.
>>>
>>> This has the side effect of changing the MIDR stored in the header of
>>> the perf.data file to no longer have masked version fields.
>> Did you consider adding a raw version of _get_cpuid(), which returns the
>> full MIDR just for the purpose of caller strcmp_cpuid_str()?
> I did, but I thought that seeing as it would only be used in one place,
> and that changing the existing one didn't break anything, that it was
> better to not fragment the CPU ID interface. I thought it might also
> have repercussions for the other architectures as well. It would also
> mean that the MIDR that's stored in the header wouldn't have the version
> information, which if we're starting to do things with that could be bad.
> 
> There are already callers of strcmp_cpuid_str() so it's probably best to
> keep it using the same get_cpuid() string. Unless there is a reason
> _not_  to do it? There isn't really anything that can't be done with it
> accepting/returning the full unmasked MIDR. If you want the old
> behavior, you just set the version fields to 0, which I've also used in
> a later patch and is already done in mapfile.csv
> 

ok, fine, so we seems that we would be following x86 on this in terms of 
using strcmp_cpuid_str(). It would be good to mention that there is 
already a weak version of strcmp_cpuid_str() for !x86 in your commit 
message.

Let me check your code again...

Thanks,
John