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Wed, 14 Jan 2026 22:50:31 -0800 (PST) Message-ID: <1d6c1473-7267-47be-930f-a5d3fb525b94@redhat.com> Date: Thu, 15 Jan 2026 14:50:08 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 07/47] arm64: mpam: Re-initialise MPAM regs when CPU comes online To: Ben Horgan Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, carl@os.amperecomputing.com, dave.martin@arm.com, david@kernel.org, dfustini@baylibre.com, fenghuay@nvidia.com, james.morse@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peternewman@google.com, punit.agrawal@oss.qualcomm.com, quic_jiles@quicinc.com, reinette.chatre@intel.com, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, tan.shaopeng@fujitsu.com, xhao@linux.alibaba.com, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, kvmarm@lists.linux.dev References: <20260112165914.4086692-1-ben.horgan@arm.com> <20260112165914.4086692-8-ben.horgan@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20260112165914.4086692-8-ben.horgan@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/13/26 12:58 AM, Ben Horgan wrote: > From: James Morse > > Now that the MPAM system registers are expected to have values that change, > reprogram them based on the previous value when a CPU is brought online. > > Previously MPAM's 'default PARTID' of 0 was always used for MPAM in > kernel-space as this is the PARTID that hardware guarantees to > reset. Because there are a limited number of PARTID, this value is exposed > to user-space, meaning resctrl changes to the resctrl default group would > also affect kernel threads. Instead, use the task's PARTID value for > kernel work on behalf of user-space too. The default of 0 is kept for both > user-space and kernel-space when MPAM is not enabled. > > Reviewed-by: Jonathan Cameron > Signed-off-by: James Morse > Signed-off-by: Ben Horgan > --- > Changes since rfc: > CONFIG_MPAM -> CONFIG_ARM64_MPAM > Check mpam_enabled > Comment about relying on ERET for synchronisation > Update commit message > --- > arch/arm64/kernel/cpufeature.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > Reviewed-by: Gavin Shan