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([39.170.101.209]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2eb39298329sm33189015ad.61.2026.11.02.18.37.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 18:37:45 -0800 (PST) From: Ping Li To: ben.horgan@arm.com, james.morse@arm.com Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, reinette.chatre@intel.com, fenghuay@nvidia.com Subject: Re: [PATCH] arm_mpam: Only program MATCH_PMG when the monitor supports it Date: Tue, 3 Nov 2026 10:37:42 +0800 Message-Id: <20261103023742.2624994-1-leeonion.muyu@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <912dbaa0-0fc0-46fb-819a-6594538b47cd@arm.com> References: <912dbaa0-0fc0-46fb-819a-6594538b47cd@arm.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Ben, Sorry to bother you again. I was looking at how the driver derives mpam_pmg_max, and I think there is a similar blind spot: mpam_msc_hw_probe() folds every MSC's MPAMF_IDR.PMG_MAX into the global mpam_pmg_max, regardless of whether the MSC has any monitors. Concretely, on our platform the DSU has no monitors and reports PMG_MAX=1. Our memory controller MSC has monitors and currently reports PMG_MAX=0, but if we later add PMG support and report PMG_MAX=31, the global value would still be clamped to 1 by the DSU, and resctrl would only expose 2 RMIDs per CLOSID instead of 32. Should the convergence only consider MSCs that have monitors? The PE-side value from MPAMIDR_EL1.PMG_MAX would still apply, as that is the maximum PMG the cores can tag traffic with. Thanks, Ping