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Mon, 9 Jan 2023 23:43:16 +0000 Received: from CY4PR11MB1862.namprd11.prod.outlook.com ([fe80::a1f7:e4c4:e60:c5b3]) by CY4PR11MB1862.namprd11.prod.outlook.com ([fe80::a1f7:e4c4:e60:c5b3%6]) with mapi id 15.20.5986.018; Mon, 9 Jan 2023 23:43:16 +0000 Message-ID: <7d752c17-1293-ea3d-505f-046dce87c2bc@intel.com> Date: Mon, 9 Jan 2023 15:43:11 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.6.1 Subject: Re: [PATCH v11 04/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag Content-Language: en-US To: Borislav Petkov , "Luck, Tony" CC: "Moger, Babu" , "corbet@lwn.net" , "tglx@linutronix.de" , "mingo@redhat.com" , "Yu, Fenghua" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "paulmck@kernel.org" , "akpm@linux-foundation.org" , "quic_neeraju@quicinc.com" , "rdunlap@infradead.org" , "damien.lemoal@opensource.wdc.com" , "songmuchun@bytedance.com" , "peterz@infradead.org" , "jpoimboe@kernel.org" , "pbonzini@redhat.com" , "Bae, Chang Seok" , "pawan.kumar.gupta@linux.intel.com" , "jmattson@google.com" , "daniel.sneddon@linux.intel.com" , "sandipan.das@amd.com" , "james.morse@arm.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "bagasdotme@gmail.com" , "Eranian, Stephane" , "christophe.leroy@csgroup.eu" , "jarkko@kernel.org" , "Hunter, Adrian" , "quic_jiles@quicinc.com" , "peternewman@google.com" References: <20230109164405.569714-1-babu.moger@amd.com> <20230109164405.569714-5-babu.moger@amd.com> <5afd0a7c-3fbe-dfea-f1b4-2fc35fbb4f13@amd.com> From: Reinette Chatre In-Reply-To: Content-Type: text/plain; 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But that has resulted in the "flags" line getting ridiculously >> long and hard for humans to read (141 fields with 926 bytes on my Skylake, >> more on more modern CPUs). > > Yap, imagine every possible CPUID bit were in there... > >> I don't know if we'd break anything if we dropped: >> >> cat_l3 cdp_l3 mba cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local >> >> from /proc/cpuinfo. > > I wouldn't mind if we remove them from cpuinfo, frankly. I am afraid that I am not aware of all the resctrl user space apps and tools being used. I did take a quick look at intel-cmt-cat that has an active user base and from what I can tell it uses /proc/cpuinfo to learn some capabilities: Example of looking for "cqm" (although "cqm" is not in Tony's list): https://github.com/intel/intel-cmt-cat/blob/master/lib/os_cap.c#L420 Example of looking for "cdp_l3": https://github.com/intel/intel-cmt-cat/blob/master/lib/os_cap.c#L520 Example of looking for "cdp_l2": https://github.com/intel/intel-cmt-cat/blob/master/lib/os_cap.c#L564 > >> Perhaps the "rule" should be written in Documentation/{somewhere}? > > This started documenting it: > > Documentation/x86/cpuinfo.rst > We could make a rule that no more resctrl related features are added to cpuinfo but I am hesitant to remove the ones that are already there. Reinette