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

[Gavin Shan <gshan@redhat.com>]

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.

> +	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.

> +	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)

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.

> +	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.

> +	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)".

> +	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)

> +		/*
> +		 * 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

> + *
> + * 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;

> +		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