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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b08369e41csm96333595ad.74.2026.03.22.21.44.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Mar 2026 21:45:11 -0700 (PDT) Message-ID: <35f92bc8-1eb1-43a0-bed2-aaac87a61c19@redhat.com> Date: Mon, 23 Mar 2026 14:44:58 +1000 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 02/40] arm_mpam: Reset when feature configuration bit unset 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, zengheng4@huawei.com, linux-doc@vger.kernel.org References: <20260313144617.3420416-1-ben.horgan@arm.com> <20260313144617.3420416-3-ben.horgan@arm.com> From: Gavin Shan In-Reply-To: <20260313144617.3420416-3-ben.horgan@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ClNu0GcLVEzPhiJ6vyNSddR-nNl7IThNLLZ9n13Y4eU_1774241112 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/14/26 12:45 AM, Ben Horgan wrote: > To indicate that the configuration, of the controls used by resctrl, in a > RIS need resetting to driver defaults the reset flags in mpam_config are > set. However, these flags are only ever set temporarily at RIS scope in > mpam_reset_ris() and hence mpam_cpu_online() will never reset these > controls to default. As the hardware reset is unknown this leads to unknown > configuration when the control values haven't been configured away from the > defaults. > > Use the policy that an unset feature configuration bit means reset. In this > way the mpam_config in the component can encode that it should be in reset > state and mpam_reprogram_msc() will reset controls as needed. > > Fixes: 09b89d2a72f3 ("arm_mpam: Allow configuration to be applied and restored during cpu online") > Signed-off-by: Ben Horgan > --- > This goes back to the initial feature configuration policy that James > used in the MPAM base driver rfc but I unfortunately > suggested him to change it. > --- > drivers/resctrl/mpam_devices.c | 40 ++++++++++------------------------ > 1 file changed, 12 insertions(+), 28 deletions(-) > Reviewed-by: Gavin Shan