openvelinux · realmzstevenmiao · Sep 17, 2026 · Mar 11, 2025 · Mar 11, 2025 · Mar 11, 2025
diff --git a/Documentation/arch/arm64/index.rst b/Documentation/arch/arm64/index.rst
@@ -20,6 +20,7 @@ ARM64 Architecture
     legacy_instructions
     memory
     memory-tagging-extension
+    mpam
     perf
     pointer-authentication
     ptdump

diff --git a/Documentation/arch/arm64/mpam.md b/Documentation/arch/arm64/mpam.md
diff --git a/Documentation/arch/arm64/mpam.rst b/Documentation/arch/arm64/mpam.rst
@@ -0,0 +1,72 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====
+MPAM
+====
+
+What is MPAM
+============
+MPAM (Memory Partitioning and Monitoring) is a feature in the CPUs and memory
+system components such as the caches or memory controllers that allow memory
+traffic to be labelled, partitioned and monitored.
+
+Traffic is labelled by the CPU, based on the control or monitor group the
+current task is assigned to using resctrl.  Partitioning policy can be set
+using the schemata file in resctrl, and monitor values read via resctrl.
+See Documentation/filesystems/resctrl.rst for more details.
+
+This allows tasks that share memory system resources, such as caches, to be
+isolated from each other according to the partitioning policy (so called noisy
+neighbours).
+
+Supported Platforms
+===================
+Use of this feature requires CPU support, support in the memory system
+components, and a description from firmware of where the MPAM device controls
+are in the MMIO address space. (e.g. the 'MPAM' ACPI table).
+
+The MMIO device that provides MPAM controls/monitors for a memory system
+component is called a memory system component. (MSC).
+
+Because the user interface to MPAM is via resctrl, only MPAM features that are
+compatible with resctrl can be exposed to user-space.
+
+MSC are considered as a group based on the topology. MSC that correspond with
+the L3 cache are considered together, it is not possible to mix MSC between L2
+and L3 to 'cover' a resctrl schema.
+
+The supported features are:
+
+* Cache portion bitmap controls (CPOR) on the L2 or L3 caches.  To expose
+  CPOR at L2 or L3, every CPU must have a corresponding CPU cache at this
+  level that also supports the feature.  Mismatched big/little platforms are
+  not supported as resctrl's controls would then also depend on task
+  placement.
+
+* Memory bandwidth maximum controls (MBW_MAX) on or after the L3 cache.
+  resctrl uses the L3 cache-id to identify where the memory bandwidth
+  control is applied. For this reason the platform must have an L3 cache
+  with cache-id's supplied by firmware. (It doesn't need to support MPAM.)
+
+  To be exported as the 'MB' schema, the topology of the group of MSC chosen
+  must match the topology of the L3 cache so that the cache-id's can be
+  repainted. For example: Platforms with Memory bandwidth maximum controls
+  on CPU-less NUMA nodes cannot expose the 'MB' schema to resctrl as these
+  nodes do not have a corresponding L3 cache. If the memory bandwidth
+  control is on the memory rather than the L3 then there must be a single
+  global L3 as otherwise it is unknown which L3 the traffic came from. There
+  must be no caches between the L3 and the memory so that the two ends of
+  the path have equivalent traffic.
+
+  When the MPAM driver finds multiple groups of MSC it can use for the 'MB'
+  schema, it prefers the group closest to the L3 cache.
+
+* Cache Storage Usage (CSU) counters can expose the 'llc_occupancy' provided
+  there is at least one CSU monitor on each MSC that makes up the L3 group.
+  Exposing CSU counters from other caches or devices is not supported.
+
+Reporting Bugs
+==============
+If you are not seeing the counters or controls you expect please share the
+debug messages produced when enabling dynamic debug and booting with:
+dyndbg="file mpam_resctrl.c +pl"
diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
@@ -242,6 +242,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | GIC-700         | #2941627        | ARM64_ERRATUM_2941627       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | CMN-650         | #3642720        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Broadcom       | Brahma-B53      | N/A             | ARM64_ERRATUM_845719        |
 +----------------+-----------------+-----------------+-----------------------------+
@@ -278,6 +280,12 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | NVIDIA         | T241 GICv3/4.x  | T241-FABRIC-4   | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T241 MPAM       | T241-MPAM-1     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T241 MPAM       | T241-MPAM-4     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T241 MPAM       | T241-MPAM-6     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
 +----------------+-----------------+-----------------+-----------------------------+

diff --git a/Documentation/arch/x86/index.rst b/Documentation/arch/x86/index.rst
@@ -31,7 +31,6 @@ x86-specific Documentation
    pti
    mds
    microcode
-   resctrl
    tsx_async_abort
    buslock
    usb-legacy-support

diff --git a/Documentation/devicetree/bindings/arm/arm,mpam-msc.yaml b/Documentation/devicetree/bindings/arm/arm,mpam-msc.yaml
diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
@@ -109,6 +109,7 @@ Documentation for filesystem implementations.
    qnx6
    ramfs-rootfs-initramfs
    relay
+   resctrl
    romfs
    smb/index
    spufs/index

diff --git a/Documentation/arch/x86/resctrl.rst → Documentation/filesystems/resctrl.rst b/Documentation/arch/x86/resctrl.rst → Documentation/filesystems/resctrl.rst
diff --git a/MAINTAINERS b/MAINTAINERS
@@ -14523,6 +14523,16 @@ S:	Maintained
 F:	Documentation/driver-api/tty/moxa-smartio.rst
 F:	drivers/tty/mxser.*
 
+MPAM DRIVER
+M:	James Morse <james.morse@arm.com>
+M:	Ben Horgan <ben.horgan@arm.com>
+R:	Reinette Chatre <reinette.chatre@intel.com>
+R:	Fenghua Yu <fenghuay@nvidia.com>
+S:	Maintained
+F:	drivers/resctrl/mpam_*
+F:	drivers/resctrl/test_mpam_*
+F:	include/linux/arm_mpam.h
+
 MR800 AVERMEDIA USB FM RADIO DRIVER
 M:	Alexey Klimov <klimov.linux@gmail.com>
 L:	linux-media@vger.kernel.org
@@ -18108,9 +18118,11 @@ M:	Fenghua Yu <fenghua.yu@intel.com>
 M:	Reinette Chatre <reinette.chatre@intel.com>
 L:	linux-kernel@vger.kernel.org
 S:	Supported
-F:	Documentation/arch/x86/resctrl*
+F:	Documentation/filesystems/resctrl.rst
 F:	arch/x86/include/asm/resctrl.h
 F:	arch/x86/kernel/cpu/resctrl/
+F:	fs/resctrl/
+F:	include/linux/resctrl*.h
 F:	tools/testing/selftests/resctrl/
 
 READ-COPY UPDATE (RCU)

diff --git a/arch/Kconfig b/arch/Kconfig
@@ -1339,10 +1339,10 @@ config ARCH_HAS_PHYS_TO_DMA
 config ARCH_HAS_CPU_RESCTRL
 	bool
 	help
-	  The 'resctrl' filesystem allows cpu controls of shared resources
-	  such as caches and memory bandwidth to be configured. An architecture
-	  selects this if it provides the arch-specific hooks for the filesystem
-	  and needs the per-task closid/rmid properties.
+	  An architecture selects this option to indicate that the necessary
+	  hooks are provided to support the common memory system usage
+	  monitoring and control interfaces provided by the 'resctrl'
+	  filesystem (see RESCTRL_FS).
 
 config HAVE_ARCH_COMPILER_H
 	bool
-Original file line number
+Diff line change
@@ Expand Up / @@ -20,6 +20,7 @@ ARM64 Architecture @@
         legacy_instructions
         memory
         memory-tagging-extension
+        mpam
         perf
         pointer-authentication
         ptdump
@@ Expand Down @@