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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35c017a161fsm139948a91.2.2026.03.23.15.36.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Mar 2026 15:36:23 -0700 (PDT) Message-ID: <078a7efe-4f5b-43b4-8252-4de36769a94a@redhat.com> Date: Tue, 24 Mar 2026 08:36:12 +1000 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 21/40] arm_mpam: resctrl: Hide CDP emulation behind CONFIG_EXPERT 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> <20260313144617.3420416-22-ben.horgan@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20260313144617.3420416-22-ben.horgan@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/14/26 12:45 AM, Ben Horgan wrote: > When CDP is not enabled, the 'rmid_entry's in the limbo list, > rmid_busy_llc, map directly to a (PARTID,PMG) pair and when CDP is enabled > the mapping is to two different pairs. As the limbo list is reused between > mounts and CDP disabled on unmount this can lead to stale mapping and the > limbo handler will then make monitor reads with potentially out of range > PARTID. This may then cause an MPAM error interrupt and the driver will > disable MPAM. > > No problems are expected if you just mount the resctrl file system > once with CDP enabled and never unmount it. Hide CDP emulation behind > CONFIG_EXPERT to protect the unwary. > > Signed-off-by: Ben Horgan > --- > Adding this ugliness in the hope of avoiding patch churn and extra > reviewer work. I am looking into the resctrl changes needed to fix this. > --- > drivers/resctrl/mpam_resctrl.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > Reviewed-by: Gavin Shan