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Tue, 21 Apr 2026 00:03:17 +0000 Date: Mon, 20 Apr 2026 17:03:13 -0700 From: "Luck, Tony" To: "Moger, Babu" CC: Reinette Chatre , Babu Moger , "corbet@lwn.net" , "Dave.Martin@arm.com" , "james.morse@arm.com" , "tglx@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "skhan@linuxfoundation.org" , "x86@kernel.org" , "hpa@zytor.com" , "peterz@infradead.org" , "juri.lelli@redhat.com" , "vincent.guittot@linaro.org" , "dietmar.eggemann@arm.com" , "rostedt@goodmis.org" , "bsegall@google.com" , "mgorman@suse.de" , "vschneid@redhat.com" , "kas@kernel.org" , "rick.p.edgecombe@intel.com" , "akpm@linux-foundation.org" , "pmladek@suse.com" , "rdunlap@infradead.org" , "dapeng1.mi@linux.intel.com" , "kees@kernel.org" , "elver@google.com" , "paulmck@kernel.org" , "lirongqing@baidu.com" , "safinaskar@gmail.com" , "fvdl@google.com" , "seanjc@google.com" , "pawan.kumar.gupta@linux.intel.com" , "xin@zytor.com" , "tiala@microsoft.com" , "chang.seok.bae@intel.com" , "Lendacky, Thomas" , "elena.reshetova@intel.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-coco@lists.linux.dev" , "kvm@vger.kernel.org" , "eranian@google.com" , "peternewman@google.com" Subject: Re: [PATCH v2 00/16] fs,x86/resctrl: Add kernel-mode (e.g., PLZA) support to the resctrl subsystem Message-ID: References: <43880b7b-b390-4e7f-8c2a-46cde9e3b051@intel.com> <5a273b0f-8225-4e9e-924e-884183734659@intel.com> <73c46024-4cf2-4f03-9268-d4378825fa87@amd.com> <973067bf-6e6c-446a-a81a-713840d701a9@intel.com> <90f4a692-1c27-4967-bf12-ec3cb597681d@amd.com> <68a551ea-d9f0-436a-9bef-e35fd027bb95@intel.com> <39e0c786-cc35-4555-bfb9-ff7cd758c423@amd.com> <99a2da36-6a21-4a99-98e0-3c9a4cf7ecf6@amd.com> Content-Type: text/plain; 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However, there is no > way to know which control group the user intends to assign to kernel mode. > All we know here is the selected mode. > > After this operation, the info/kernel_mode_assignment interface should > become visible. But the question is: what should it contain or point to at > this moment? > > # cat info/kernel_mode_assignment > ?? > > Next operation: Assign the group > > # echo "ctrl1//" > info/kernel_mode_assignment Now ring0 code is using the CLOSID from the ctrl1 group. But the RMID for this group isn't used. Are we OK with "wasting" an RMID in this way? Maybe it doesn't matter too much for AMD as you would just avoid assigning any counters to this group. But should Intel get around to doing PLZA-like functionality, that's a real loss of an RMID that might be useful elsewhere. -Tony