Re: [PATCH 09/33] ACPI / MPAM: Parse the MPAM table

[Ben Horgan <ben.horgan@arm.com>]

Hi Gavin,

On 11/8/25 08:54, Gavin Shan wrote:
> Hi Ben,
> 
> On 11/7/25 10:34 PM, Ben Horgan wrote:
>> From: James Morse <james.morse@arm.com>
>>
>> Add code to parse the arm64 specific MPAM table, looking up the cache
>> level from the PPTT and feeding the end result into the MPAM driver.
>>
>> This happens in two stages. Platform devices are created first for the
>> MSC devices. Once the driver probes it calls acpi_mpam_parse_resources()
>> to discover the RIS entries the MSC contains.
>>
>> For now the MPAM hook mpam_ris_create() is stubbed out, but will update
>> the MPAM driver with optional discovered data about the RIS entries.
>>
>> CC: Carl Worth <carl@os.amperecomputing.com>
>> Link: https://developer.arm.com/documentation/den0065/3-0bet/?lang=en
>> Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
>> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
>> Tested-by: Peter Newman <peternewman@google.com>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
>> ---
>> Changes since v3:
>> return irq from acpi_mpam_register_irq (Jonathan)
>> err -> len rename (Jonathan)
>> Move table initialisation after checking (Jonathan)
>> Add sanity checking in acpi_mpam_count_msc() (Jonathan)
>> ---
>>   arch/arm64/Kconfig          |   1 +
>>   drivers/acpi/arm64/Kconfig  |   3 +
>>   drivers/acpi/arm64/Makefile |   1 +
>>   drivers/acpi/arm64/mpam.c   | 403 ++++++++++++++++++++++++++++++++++++
>>   drivers/acpi/tables.c       |   2 +-
>>   include/linux/arm_mpam.h    |  47 +++++
>>   6 files changed, 456 insertions(+), 1 deletion(-)
>>   create mode 100644 drivers/acpi/arm64/mpam.c
>>   create mode 100644 include/linux/arm_mpam.h
>>
> 
> With the following minor comments addressed:
> 
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> 
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 67015d51f7b5..c5e66d5d72cd 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -2025,6 +2025,7 @@ config ARM64_TLB_RANGE
>>     config ARM64_MPAM
>>       bool "Enable support for MPAM"
>> +    select ACPI_MPAM if ACPI
>>       help
>>         Memory System Resource Partitioning and Monitoring (MPAM) is an
>>         optional extension to the Arm architecture that allows each
>> diff --git a/drivers/acpi/arm64/Kconfig b/drivers/acpi/arm64/Kconfig
>> index b3ed6212244c..f2fd79f22e7d 100644
>> --- a/drivers/acpi/arm64/Kconfig
>> +++ b/drivers/acpi/arm64/Kconfig
>> @@ -21,3 +21,6 @@ config ACPI_AGDI
>>     config ACPI_APMT
>>       bool
>> +
>> +config ACPI_MPAM
>> +    bool
>> diff --git a/drivers/acpi/arm64/Makefile b/drivers/acpi/arm64/Makefile
>> index 05ecde9eaabe..9390b57cb564 100644
>> --- a/drivers/acpi/arm64/Makefile
>> +++ b/drivers/acpi/arm64/Makefile
>> @@ -4,6 +4,7 @@ obj-$(CONFIG_ACPI_APMT)     += apmt.o
>>   obj-$(CONFIG_ACPI_FFH)        += ffh.o
>>   obj-$(CONFIG_ACPI_GTDT)     += gtdt.o
>>   obj-$(CONFIG_ACPI_IORT)     += iort.o
>> +obj-$(CONFIG_ACPI_MPAM)     += mpam.o
>>   obj-$(CONFIG_ACPI_PROCESSOR_IDLE) += cpuidle.o
>>   obj-$(CONFIG_ARM_AMBA)        += amba.o
>>   obj-y                += dma.o init.o
>> diff --git a/drivers/acpi/arm64/mpam.c b/drivers/acpi/arm64/mpam.c
>> new file mode 100644
>> index 000000000000..c199944862ed
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/mpam.c
>> @@ -0,0 +1,403 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +// Copyright (C) 2025 Arm Ltd.
>> +
>> +/* Parse the MPAM ACPI table feeding the discovered nodes into the
>> driver */
>> +
>> +#define pr_fmt(fmt) "ACPI MPAM: " fmt
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/arm_mpam.h>
>> +#include <linux/bits.h>
>> +#include <linux/cpu.h>
>> +#include <linux/cpumask.h>
>> +#include <linux/platform_device.h>
>> +
>> +#include <acpi/processor.h>
>> +
>> +/*
>> + * Flags for acpi_table_mpam_msc.*_interrupt_flags.
>> + * See 2.1.1 Interrupt Flags, Table 5, of DEN0065B_MPAM_ACPI_3.0-bet.
>> + */
>> +#define ACPI_MPAM_MSC_IRQ_MODE                              BIT(0)
>> +#define ACPI_MPAM_MSC_IRQ_TYPE_MASK                        
>> GENMASK(2, 1)
>> +#define ACPI_MPAM_MSC_IRQ_TYPE_WIRED                        0
>> +#define ACPI_MPAM_MSC_IRQ_AFFINITY_TYPE_MASK                BIT(3)
>> +#define ACPI_MPAM_MSC_IRQ_AFFINITY_TYPE_PROCESSOR           0
>> +#define ACPI_MPAM_MSC_IRQ_AFFINITY_TYPE_PROCESSOR_CONTAINER 1
>> +#define ACPI_MPAM_MSC_IRQ_AFFINITY_VALID                    BIT(4)
>> +
>> +/*
>> + * Encodings for the MSC node body interface type field.
>> + * See 2.1 MPAM MSC node, Table 4 of DEN0065B_MPAM_ACPI_3.0-bet.
>> + */
>> +#define ACPI_MPAM_MSC_IFACE_MMIO   0x00
>> +#define ACPI_MPAM_MSC_IFACE_PCC    0x0a
>> +
>> +static bool _is_ppi_partition(u32 flags)
>> +{
>> +    u32 aff_type, is_ppi;
>> +    bool ret;
>> +
>> +    is_ppi = FIELD_GET(ACPI_MPAM_MSC_IRQ_AFFINITY_VALID, flags);
>> +    if (!is_ppi)
>> +        return false;
>> +
> 
> A error message may be needed since the driver won't fully function without
> interrupt enabled. The error message gives a clear indication on what has
> happened to system administrator.

I don't think extra error messages are needed as the error interrupts
can only be caused by driver programming errors and overflow interrupts
are currently not considered.

> 
>> +    aff_type = FIELD_GET(ACPI_MPAM_MSC_IRQ_AFFINITY_TYPE_MASK, flags);
>> +    ret = (aff_type ==
>> ACPI_MPAM_MSC_IRQ_AFFINITY_TYPE_PROCESSOR_CONTAINER);
>> +    if (ret)
>> +        pr_err_once("Partitioned interrupts not supported\n");
>> +
>> +    return ret;
>> +}
>> +
>> +static int acpi_mpam_register_irq(struct platform_device *pdev,
>> +                  int intid, u32 flags)
>> +{
> 
> s/int intid/u32 intid
> 
> All the callers pass a 'u32' parameter instead of 'int'.
> 
>> +    int irq;
>> +    u32 int_type;
>> +    int trigger;
>> +
>> +    if (!intid)
>> +        return -EINVAL;
>> +
>> +    if (_is_ppi_partition(flags))
>> +        return -EINVAL;
>> +
>> +    trigger = FIELD_GET(ACPI_MPAM_MSC_IRQ_MODE, flags);
>> +    int_type = FIELD_GET(ACPI_MPAM_MSC_IRQ_TYPE_MASK, flags);
>> +    if (int_type != ACPI_MPAM_MSC_IRQ_TYPE_WIRED)
>> +        return -EINVAL;
>> +
> 
> Same as above, a error message may be needed here.

I'd rather leave this as is, see above.

> 
>> +    irq = acpi_register_gsi(&pdev->dev, intid, trigger,
>> ACPI_ACTIVE_HIGH);
>> +    if (irq <= 0)
>> +        pr_err_once("Failed to register interrupt 0x%x with ACPI\n",
>> intid);
>> +
> 
> s/if (irq <= 0)/if (irq < 0)

Done

> 
> It's impossible for acpi_register_gsi() to return 0, which has been
> translated
> to -EINVAL in the function.
> 
>> +    return irq;
>> +}
>> +
>> +static void acpi_mpam_parse_irqs(struct platform_device *pdev,
>> +                 struct acpi_mpam_msc_node *tbl_msc,
>> +                 struct resource *res, int *res_idx)
>> +{
>> +    u32 flags, intid;
>> +    int irq;
>> +
>> +    intid = tbl_msc->overflow_interrupt;
>> +    flags = tbl_msc->overflow_interrupt_flags;
>> +    irq = acpi_mpam_register_irq(pdev, intid, flags);
>> +    if (irq > 0)
>> +        res[(*res_idx)++] = DEFINE_RES_IRQ_NAMED(irq, "overflow");
>> +
>> +    intid = tbl_msc->error_interrupt;
>> +    flags = tbl_msc->error_interrupt_flags;
>> +    irq = acpi_mpam_register_irq(pdev, intid, flags);
>> +    if (irq > 0)
>> +        res[(*res_idx)++] = DEFINE_RES_IRQ_NAMED(irq, "error");
>> +}
>> +
>> +static int acpi_mpam_parse_resource(struct mpam_msc *msc,
>> +                    struct acpi_mpam_resource_node *res)
>> +{
>> +    int level, nid;
>> +    u32 cache_id;
>> +
>> +    switch (res->locator_type) {
>> +    case ACPI_MPAM_LOCATION_TYPE_PROCESSOR_CACHE:
>> +        cache_id = res->locator.cache_locator.cache_reference;
>> +        level = find_acpi_cache_level_from_id(cache_id);
>> +        if (level <= 0) {
>> +            pr_err_once("Bad level (%d) for cache with id %u\n",
>> level, cache_id);
>> +            return -EINVAL;
>> +        }
>> +        return mpam_ris_create(msc, res->ris_index, MPAM_CLASS_CACHE,
>> +                       level, cache_id);
>> +    case ACPI_MPAM_LOCATION_TYPE_MEMORY:
>> +        nid = pxm_to_node(res->locator.memory_locator.proximity_domain);
>> +        if (nid == NUMA_NO_NODE) {
>> +            pr_debug("Bad proxmity domain %lld, using node 0 instead\n",
>> +                 res->locator.memory_locator.proximity_domain);
>> +            nid = 0;
>> +        }
>> +        return mpam_ris_create(msc, res->ris_index, MPAM_CLASS_MEMORY,
>> +                       255, nid);
>> +    default:
>> +        /* These get discovered later and are treated as unknown */
>> +        return 0;
>> +    }
>> +}
>> +
>> +int acpi_mpam_parse_resources(struct mpam_msc *msc,
>> +                  struct acpi_mpam_msc_node *tbl_msc)
>> +{
>> +    int i, err;
>> +    char *ptr, *table_end;
>> +    struct acpi_mpam_resource_node *resource;
>> +
>> +    ptr = (char *)(tbl_msc + 1);
>> +    table_end = ptr + tbl_msc->length;
>> +    for (i = 0; i < tbl_msc->num_resource_nodes; i++) {
>> +        u64 max_deps, remaining_table;
>> +
>> +        if (ptr + sizeof(*resource) > table_end)
>> +            return -EINVAL;
>> +
>> +        resource = (struct acpi_mpam_resource_node *)ptr;
>> +
>> +        remaining_table = table_end - ptr;
>> +        max_deps = remaining_table / sizeof(struct acpi_mpam_func_deps);
>> +        if (resource->num_functional_deps > max_deps) {
>> +            pr_debug("MSC has impossible number of functional
>> dependencies\n");
>> +            return -EINVAL;
>> +        }
>> +
>> +        err = acpi_mpam_parse_resource(msc, resource);
>> +        if (err)
>> +            return err;
>> +
>> +        ptr += sizeof(*resource);
>> +        ptr += resource->num_functional_deps * sizeof(struct
>> acpi_mpam_func_deps);
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +/*
>> + * Creates the device power management link and returns true if the
>> + * acpi id is valid and usable for cpu affinity.  This is the case
>> + * when the linked device is a processor or a processor container.
>> + */
>> +static bool __init parse_msc_pm_link(struct acpi_mpam_msc_node *tbl_msc,
>> +                     struct platform_device *pdev,
>> +                     u32 *acpi_id)
>> +{
>> +    char hid[sizeof(tbl_msc->hardware_id_linked_device) + 1] = { 0 };
>> +    bool acpi_id_valid = false;
>> +    struct acpi_device *buddy;
>> +    char uid[11];
>> +    int len;
>> +
>> +    memcpy(hid, &tbl_msc->hardware_id_linked_device,
>> +           sizeof(tbl_msc->hardware_id_linked_device));
>> +
>> +    if (!strcmp(hid, ACPI_PROCESSOR_CONTAINER_HID)) {
>> +        *acpi_id = tbl_msc->instance_id_linked_device;
>> +        acpi_id_valid = true;
>> +    }
>> +
>> +    len = snprintf(uid, sizeof(uid), "%u",
>> +               tbl_msc->instance_id_linked_device);
>> +    if (len >= sizeof(uid)) {
>> +        pr_debug("Failed to convert uid of device for power
>> management.");
>> +        return acpi_id_valid;
>> +    }
>> +
>> +    buddy = acpi_dev_get_first_match_dev(hid, uid, -1);
>> +    if (buddy)
>> +        device_link_add(&pdev->dev, &buddy->dev, DL_FLAG_STATELESS);
>> +
>> +    return acpi_id_valid;
>> +}
>> +
>> +static int decode_interface_type(struct acpi_mpam_msc_node *tbl_msc,
>> +                 enum mpam_msc_iface *iface)
>> +{
>> +    switch (tbl_msc->interface_type) {
>> +    case ACPI_MPAM_MSC_IFACE_MMIO:
>> +        *iface = MPAM_IFACE_MMIO;
>> +        return 0;
>> +    case ACPI_MPAM_MSC_IFACE_PCC:
>> +        *iface = MPAM_IFACE_PCC;
>> +        return 0;
>> +    default:
>> +        return -EINVAL;
>> +    }
>> +}
>> +
>> +static struct platform_device * __init acpi_mpam_parse_msc(struct
>> acpi_mpam_msc_node *tbl_msc)
>> +{
>> +    struct platform_device *pdev __free(platform_device_put) =
>> +        platform_device_alloc("mpam_msc", tbl_msc->identifier);
>> +    int next_res = 0, next_prop = 0, err;
>> +    /* pcc, nrdy, affinity and a sentinel */
>> +    struct property_entry props[4] = { 0 };
>> +    /* mmio, 2xirq, no sentinel. */
>> +    struct resource res[3] = { 0 };
>> +    struct acpi_device *companion;
>> +    enum mpam_msc_iface iface;
>> +    char uid[16];
>> +    u32 acpi_id;
>> +
>> +    if (!pdev)
>> +        return ERR_PTR(-ENOMEM);
>> +
>> +    /* Some power management is described in the namespace: */
>> +    err = snprintf(uid, sizeof(uid), "%u", tbl_msc->identifier);
>> +    if (err > 0 && err < sizeof(uid)) {
>> +        companion = acpi_dev_get_first_match_dev("ARMHAA5C", uid, -1);
>> +        if (companion)
>> +            ACPI_COMPANION_SET(&pdev->dev, companion);
>> +        else
>> +            pr_debug("MSC.%u: missing namespace entry\n",
>> +                 tbl_msc->identifier);
>> +    }
>> +
> 
> { } is needed for the block of code spanning multiple lines.

Just made it one line.

> 
>> +    if (decode_interface_type(tbl_msc, &iface)) {
>> +        pr_debug("MSC.%u: unknown interface type\n", tbl_msc-
>> >identifier);
>> +        return ERR_PTR(-EINVAL);
>> +    }
>> +
>> +    if (iface == MPAM_IFACE_MMIO)
>> +        res[next_res++] = DEFINE_RES_MEM_NAMED(tbl_msc->base_address,
>> +                               tbl_msc->mmio_size,
>> +                               "MPAM:MSC");
>> +    else if (iface == MPAM_IFACE_PCC)
>> +        props[next_prop++] = PROPERTY_ENTRY_U32("pcc-channel",
>> +                            tbl_msc->base_address);
>> +
> 
> As above, {} is needed here.

Done

> 
>> +    acpi_mpam_parse_irqs(pdev, tbl_msc, res, &next_res);
>> +
>> +    WARN_ON_ONCE(next_res > ARRAY_SIZE(res));
>> +    err = platform_device_add_resources(pdev, res, next_res);
>> +    if (err)
>> +        return ERR_PTR(err);
>> +
>> +    props[next_prop++] = PROPERTY_ENTRY_U32("arm,not-ready-us",
>> +                        tbl_msc->max_nrdy_usec);
>> +
>> +    /*
>> +     * The MSC's CPU affinity is described via its linked power
>> +     * management device, but only if it points at a Processor or
>> +     * Processor Container.
>> +     */
>> +    if (parse_msc_pm_link(tbl_msc, pdev, &acpi_id))
>> +        props[next_prop++] = PROPERTY_ENTRY_U32("cpu_affinity",
>> acpi_id);
>> +
>> +    WARN_ON_ONCE(next_prop > ARRAY_SIZE(props));
>> +    err = device_create_managed_software_node(&pdev->dev, props, NULL);
>> +    if (err)
>> +        return ERR_PTR(err);
>> +
>> +    /*
>> +     * Stash the table entry for acpi_mpam_parse_resources() to discover
>> +     * what this MSC controls.
>> +     */
>> +    err = platform_device_add_data(pdev, tbl_msc, tbl_msc->length);
>> +    if (err)
>> +        return ERR_PTR(err);
>> +
>> +    err = platform_device_add(pdev);
>> +    if (err)
>> +        return ERR_PTR(err);
>> +
>> +    return_ptr(pdev);
>> +}
>> +
>> +static int __init acpi_mpam_parse(void)
>> +{
>> +    char *table_end, *table_offset;
>> +    struct acpi_mpam_msc_node *tbl_msc;
>> +    struct platform_device *pdev;
>> +
>> +    if (acpi_disabled || !system_supports_mpam())
>> +        return 0;
>> +
>> +    struct acpi_table_header *table __free(acpi_put_table) =
>> +        acpi_get_table_ret(ACPI_SIG_MPAM, 0);
>> +
>> +    if (IS_ERR(table))
>> +        return 0;
>> +
>> +    if (table->revision < 1)
>> +        return 0;
>> +
> 
> It's correct to return zero on IS_ERR(table) with an error message, but
> a message printed by pr_debug() may be worthywhile on "if (table-
>>revison < 1)".

Ok, adding:
pr_debug("MPAM ACPI table revision %d not supported\n",
          table->revision);

> 
>> +    table_offset = (char *)(table + 1);
>> +    table_end = (char *)table + table->length;
>> +
>> +    while (table_offset < table_end) {
>> +        tbl_msc = (struct acpi_mpam_msc_node *)table_offset;
>> +        table_offset += tbl_msc->length;
>> +
>> +        if (table_offset > table_end) {
>> +            pr_err("MSC entry overlaps end of ACPI table\n");
>> +            return -EINVAL;
>> +        }
>> +
> 
> Would be:
> 
>         if (table_offset + sizeof(*tbl_msc) > table_end)

As Jonathan said I don't think this is quite valid but we can add a
check that makes sure ->length is within the table bounds. I've changed
this to be:

tbl_msc = (struct acpi_mpam_msc_node *)table_offset;
if (table_offset + sizeof(*tbl_msc) > table_end ||
    table_offset + tbl_msc->length > table_end) {
	pr_err("MSC entry overlaps end of ACPI table\n");
		return -EINVAL;
}
table_offset += tbl_msc->length;

> 
>> +        /*
>> +         * If any of the reserved fields are set, make no attempt to
>> +         * parse the MSC structure. This MSC will still be counted by
>> +         * acpi_mpam_count_msc(), meaning the MPAM driver can't probe
>> +         * against all MSC, and will never be enabled. There is no way
>> +         * to enable it safely, because we cannot determine safe
>> +         * system-wide partid and pmg ranges in this situation.
>> +         */
>> +        if (tbl_msc->reserved || tbl_msc->reserved1 || tbl_msc-
>> >reserved2) {
>> +            pr_err_once("Unrecognised MSC, MPAM not usable\n");
>> +            pr_debug("MSC.%u: reserved field set\n", tbl_msc-
>> >identifier);
>> +            continue;
>> +        }
>> +
>> +        if (!tbl_msc->mmio_size) {
>> +            pr_debug("MSC.%u: marked as disabled\n", tbl_msc-
>> >identifier);
>> +            continue;
>> +        }
>> +
>> +        pdev = acpi_mpam_parse_msc(tbl_msc);
>> +        if (IS_ERR(pdev))
>> +            return PTR_ERR(pdev);
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +/**
>> + * acpi_mpam_count_msc() - Count the number of MSC described by
>> firmware.
>> + *
>> + * Returns the number of MSC, or zero for an error.
> 
> s/MSC/MSCs

Ack

> 
>> + *
>> + * This can be called before or in parallel with acpi_mpam_parse().
>> + */
>> +int acpi_mpam_count_msc(void)
>> +{
>> +    char *table_end, *table_offset;
>> +    struct acpi_mpam_msc_node *tbl_msc;
>> +    int count = 0;
>> +
>> +    if (acpi_disabled || !system_supports_mpam())
>> +        return 0;
>> +
>> +    struct acpi_table_header *table __free(acpi_put_table) =
>> +        acpi_get_table_ret(ACPI_SIG_MPAM, 0);
>> +
>> +    if (IS_ERR(table))
>> +        return 0;
>> +
>> +    if (table->revision < 1)
>> +        return 0;
>> +
>> +    table_offset = (char *)(table + 1);
>> +    table_end = (char *)table + table->length;
>> +
>> +    while (table_offset < table_end) {
>> +        tbl_msc = (struct acpi_mpam_msc_node *)table_offset;
>> +
> 
> Would be worthy to check:
> 
>         if (table_offset + sizeof(*tbl_msc) > table_end)
>             return -EINVAL;

Ok, it will ensure tbl_msc->length exists.

> 
>> +        if (tbl_msc->length < sizeof(*tbl_msc))
>> +            return -EINVAL;
>> +        if (tbl_msc->length > table_end - table_offset)
>> +            return -EINVAL;
>> +        table_offset += tbl_msc->length;
>> +
>> +        if (!tbl_msc->mmio_size)
>> +            continue;
>> +
>> +        count++;
>> +    }
>> +
>> +    return count;
>> +}
>> +
>> +/*
>> + * Call after ACPI devices have been created, which happens behind
>> acpi_scan_init()
>> + * called from subsys_initcall(). PCC requires the mailbox driver,
>> which is
>> + * initialised from postcore_initcall().
>> + */
>> +subsys_initcall_sync(acpi_mpam_parse);
>> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
>> index 57fc8bc56166..4286e4af1092 100644
>> --- a/drivers/acpi/tables.c
>> +++ b/drivers/acpi/tables.c
>> @@ -408,7 +408,7 @@ static const char table_sigs[][ACPI_NAMESEG_SIZE]
>> __nonstring_array __initconst
>>       ACPI_SIG_PSDT, ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT,
>>       ACPI_SIG_IORT, ACPI_SIG_NFIT, ACPI_SIG_HMAT, ACPI_SIG_PPTT,
>>       ACPI_SIG_NHLT, ACPI_SIG_AEST, ACPI_SIG_CEDT, ACPI_SIG_AGDI,
>> -    ACPI_SIG_NBFT, ACPI_SIG_SWFT};
>> +    ACPI_SIG_NBFT, ACPI_SIG_SWFT, ACPI_SIG_MPAM};
>>     #define ACPI_HEADER_SIZE sizeof(struct acpi_table_header)
>>   diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
>> new file mode 100644
>> index 000000000000..a3828ef91aee
>> --- /dev/null
>> +++ b/include/linux/arm_mpam.h
>> @@ -0,0 +1,47 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/* Copyright (C) 2025 Arm Ltd. */
>> +
>> +#ifndef __LINUX_ARM_MPAM_H
>> +#define __LINUX_ARM_MPAM_H
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/types.h>
>> +
>> +#define GLOBAL_AFFINITY        ~0
>> +
>> +struct mpam_msc;
>> +
>> +enum mpam_msc_iface {
>> +    MPAM_IFACE_MMIO,    /* a real MPAM MSC */
>> +    MPAM_IFACE_PCC,        /* a fake MPAM MSC */
>> +};
>> +
>> +enum mpam_class_types {
>> +    MPAM_CLASS_CACHE,       /* Caches, e.g. L2, L3 */
>> +    MPAM_CLASS_MEMORY,      /* Main memory */
>> +    MPAM_CLASS_UNKNOWN,     /* Everything else, e.g. SMMU */
>> +};
>> +
>> +#ifdef CONFIG_ACPI_MPAM
>> +int acpi_mpam_parse_resources(struct mpam_msc *msc,
>> +                  struct acpi_mpam_msc_node *tbl_msc);
>> +
>> +int acpi_mpam_count_msc(void);
>> +#else
>> +static inline int acpi_mpam_parse_resources(struct mpam_msc *msc,
>> +                        struct acpi_mpam_msc_node *tbl_msc)
>> +{
>> +    return -EINVAL;
>> +}
>> +
>> +static inline int acpi_mpam_count_msc(void) { return -EINVAL; }
>> +#endif
>> +
>> +static inline int mpam_ris_create(struct mpam_msc *msc, u8 ris_idx,
>> +                  enum mpam_class_types type, u8 class_id,
>> +                  int component_id)
>> +{
>> +    return -EINVAL;
>> +}
>> +
>> +#endif /* __LINUX_ARM_MPAM_H */
> 
> Thanks,
> Gavin
> 

-- 
Thanks,

Ben