Hi James,
On Fri, Oct 17, 2025 at 8:57 PM James Morse <james.morse@arm.com> wrote:
>
> Hello,
>
> A slew of minor changes, nothing really sticks out.
> Changes are noted on each patch.
>
> ~
>
> This is just enough MPAM driver for ACPI. DT got ripped out. If you need DT
> support - please share your DTS so the DT folk know the binding is what is
> needed.
> This doesn't contain any of the resctrl code, meaning you can't actually drive it
> from user-space yet. Because of that, its hidden behind CONFIG_EXPERT.
> This will change once the user interface is connected up.
>
> This is the initial group of patches that allows the resctrl code to be built
> on top. Including that will increase the number of trees that may need to
> coordinate, so breaking it up make sense.
>
> The locking got simplified, but is still strange - this is because of the 'mpam-fb'
> firmware interface specification that is still alpha. That thing needs to wait for
> an interrupt after every system register write, which significantly impacts the
> driver. Some features just won't work, e.g. reading the monitor registers via
> perf.
>
> I've not found a platform that can test all the behaviours around the monitors,
> so this is where I'd expect the most bugs.
>
> The MPAM spec that describes all the system and MMIO registers can be found here:
> https://developer.arm.com/documentation/ddi0598/db/?lang=en
> (Ignored the 'RETIRED' warning - that is just arm moving the documentation around.
> This document has the best overview)
>
> The expectation is this will go via the arm64 tree.
>
>
> This series is based on v6.18-rc4, and can be retrieved from:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/driver/v3
>
> The rest of the driver can be found here:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/snapshot/v6.18-rc1
>
> What is MPAM? Set your time-machine to 2020:
> https://lore.kernel.org/lkml/20201030161120.227225-1-james.morse@arm.com/
>
> This series was previously posted here:
> [v2] lore.kernel.org/r/20250910204309.20751-1-james.morse@arm.com
> [v1] lore.kernel.org/r/20250822153048.2287-1-james.morse@arm.com
> [RFC] lore.kernel.org/r/20250711183648.30766-2-james.morse@arm.com
>
>
> James Morse (27):
> ACPI / PPTT: Add a helper to fill a cpumask from a processor container
> ACPI / PPTT: Stop acpi_count_levels() expecting callers to clear
> levels
> ACPI / PPTT: Find cache level by cache-id
> ACPI / PPTT: Add a helper to fill a cpumask from a cache_id
> arm64: kconfig: Add Kconfig entry for MPAM
> ACPI / MPAM: Parse the MPAM table
> arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate
> arm_mpam: Add the class and component structures for firmware
> described ris
> arm_mpam: Add MPAM MSC register layout definitions
> arm_mpam: Add cpuhp callbacks to probe MSC hardware
> arm_mpam: Probe hardware to find the supported partid/pmg values
> arm_mpam: Add helpers for managing the locking around the mon_sel
> registers
> arm_mpam: Probe the hardware features resctrl supports
> arm_mpam: Merge supported features during mpam_enable() into
> mpam_class
> arm_mpam: Reset MSC controls from cpuhp callbacks
> arm_mpam: Add a helper to touch an MSC from any CPU
> arm_mpam: Extend reset logic to allow devices to be reset any time
> arm_mpam: Register and enable IRQs
> arm_mpam: Use a static key to indicate when mpam is enabled
> arm_mpam: Allow configuration to be applied and restored during cpu
> online
> arm_mpam: Probe and reset the rest of the features
> arm_mpam: Add helpers to allocate monitors
> arm_mpam: Add mpam_msmon_read() to read monitor value
> arm_mpam: Track bandwidth counter state for overflow and power
> management
> arm_mpam: Add helper to reset saved mbwu state
> arm_mpam: Add kunit test for bitmap reset
> arm_mpam: Add kunit tests for props_mismatch()
>
> Rohit Mathew (2):
> arm_mpam: Probe for long/lwd mbwu counters
> arm_mpam: Use long MBWU counters if supported
>
> arch/arm64/Kconfig | 25 +
> drivers/Kconfig | 2 +
> drivers/Makefile | 1 +
> drivers/acpi/arm64/Kconfig | 3 +
> drivers/acpi/arm64/Makefile | 1 +
> drivers/acpi/arm64/mpam.c | 384 ++++
> drivers/acpi/pptt.c | 248 ++-
> drivers/acpi/tables.c | 2 +-
> drivers/resctrl/Kconfig | 22 +
> drivers/resctrl/Makefile | 4 +
> drivers/resctrl/mpam_devices.c | 2701 +++++++++++++++++++++++++++
> drivers/resctrl/mpam_internal.h | 661 +++++++
> drivers/resctrl/test_mpam_devices.c | 389 ++++
> include/linux/acpi.h | 26 +
> include/linux/arm_mpam.h | 58 +
> include/linux/platform_device.h | 1 +
> 16 files changed, 4519 insertions(+), 9 deletions(-)
> create mode 100644 drivers/acpi/arm64/mpam.c
> create mode 100644 drivers/resctrl/Kconfig
> create mode 100644 drivers/resctrl/Makefile
> create mode 100644 drivers/resctrl/mpam_devices.c
> create mode 100644 drivers/resctrl/mpam_internal.h
> create mode 100644 drivers/resctrl/test_mpam_devices.c
> create mode 100644 include/linux/arm_mpam.h
>
> --
> 2.39.5
>
I applied this series and booted the kernel on a Google Cloud C4A host
(baremetal) and confirmed through sysfs that all MSCs were probed
successfully.
Tested-by: Peter Newman <peternewman@google.com>
Thanks!
-Peter