Re: [PATCH v2 06/29] ACPI / MPAM: Parse the MPAM table

[Fenghua Yu <fenghuay@nvidia.com>]

Hi, James,

On 9/10/25 13:42, James Morse wrote:
> 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.
>
> For now the MPAM hook mpam_ris_create() is stubbed out, but will update
> the MPAM driver with optional discovered data.
>
> CC: Carl Worth <carl@os.amperecomputing.com>
> Link: https://developer.arm.com/documentation/den0065/3-0bet/?lang=en
> Signed-off-by: James Morse <james.morse@arm.com>
>
> ---
> Changes since v1:
>   * Whitespace.
>   * Gave GLOBAL_AFFINITY a pre-processor'd name.
>   * Fixed assumption that there are zero functional dependencies.
>   * Bounds check walking of the MSC RIS.
>   * More bounds checking in the main table walk.
>   * Check for nonsense numbers of function dependencies.
>   * Smattering of pr_debug() to help folk feeding line-noise to the parser.
>   * Changed the comment flavour on the SPDX string.
>   * Removed additional table check.
>   * More comment wrangling.
>
> Changes since RFC:
>   * Used DEFINE_RES_IRQ_NAMED() and friends macros.
>   * Additional error handling.
>   * Check for zero sized MSC.
>   * Allow table revisions greater than 1. (no spec for revision 0!)
>   * Use cleanup helpers to retrive ACPI tables, which allows some functions
>     to be folded together.
> ---
>   arch/arm64/Kconfig          |   1 +
>   drivers/acpi/arm64/Kconfig  |   3 +
>   drivers/acpi/arm64/Makefile |   1 +
>   drivers/acpi/arm64/mpam.c   | 361 ++++++++++++++++++++++++++++++++++++
>   drivers/acpi/tables.c       |   2 +-
>   include/linux/acpi.h        |  12 ++
>   include/linux/arm_mpam.h    |  48 +++++
>   7 files changed, 427 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/acpi/arm64/mpam.c
>   create mode 100644 include/linux/arm_mpam.h
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 4be8a13505bf..6487c511bdc6 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -2062,6 +2062,7 @@ 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..fd9cfa143676
> --- /dev/null
> +++ b/drivers/acpi/arm64/mpam.c
> @@ -0,0 +1,361 @@
> +// 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_MASK                    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_PROCESSOR_CONTAINER BIT(3)
> +#define ACPI_MPAM_MSC_IRQ_AFFINITY_VALID               BIT(4)
> +
> +static bool acpi_mpam_register_irq(struct platform_device *pdev, int intid,
> +				   u32 flags, int *irq,
> +				   u32 processor_container_uid)
> +{
> +	int sense;
> +
> +	if (!intid)
> +		return false;
> +
> +	if (FIELD_GET(ACPI_MPAM_MSC_IRQ_TYPE_MASK, flags) !=
> +	    ACPI_MPAM_MSC_IRQ_TYPE_WIRED)
> +		return false;
> +
> +	sense = FIELD_GET(ACPI_MPAM_MSC_IRQ_MODE_MASK, flags);
> +
> +	if (16 <= intid && intid < 32 && processor_container_uid != GLOBAL_AFFINITY) {
> +		pr_err_once("Partitioned interrupts not supported\n");
> +		return false;
> +	}
> +
> +	*irq = acpi_register_gsi(&pdev->dev, intid, sense, ACPI_ACTIVE_HIGH);
> +	if (*irq <= 0) {
> +		pr_err_once("Failed to register interrupt 0x%x with ACPI\n",
> +			    intid);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +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, aff;
> +	int irq;
> +
> +	flags = tbl_msc->overflow_interrupt_flags;
> +	if (flags & ACPI_MPAM_MSC_IRQ_AFFINITY_VALID &&
> +	    flags & ACPI_MPAM_MSC_IRQ_AFFINITY_PROCESSOR_CONTAINER)
> +		aff = tbl_msc->overflow_interrupt_affinity;
> +	else
> +		aff = GLOBAL_AFFINITY;
> +	if (acpi_mpam_register_irq(pdev, tbl_msc->overflow_interrupt, flags, &irq, aff))
> +		res[(*res_idx)++] = DEFINE_RES_IRQ_NAMED(irq, "overflow");
> +
> +	flags = tbl_msc->error_interrupt_flags;
> +	if (flags & ACPI_MPAM_MSC_IRQ_AFFINITY_VALID &&
> +	    flags & ACPI_MPAM_MSC_IRQ_AFFINITY_PROCESSOR_CONTAINER)
> +		aff = tbl_msc->error_interrupt_affinity;
> +	else
> +		aff = GLOBAL_AFFINITY;
> +	if (acpi_mpam_register_irq(pdev, tbl_msc->error_interrupt, flags, &irq, aff))
> +		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 (%u) for cache with id %u\n", level, cache_id);

Since level could be negative value here, printing it as %u converts it 
to positive value and will cause debug difficulty. For example, -ENOENT 
returned by find_acpi_cache_level_from_id() will be printed as 
4294967294(instead of -2) which is hard to know the error code.

Suggest to change this to %d:

			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)
> +			nid = 0;
> +		return mpam_ris_create(msc, res->ris_index, MPAM_CLASS_MEMORY,
> +				       255, nid);
> +	default:
> +		/* These get discovered later and 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;
> +}
> +
> +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];
> +	bool acpi_id_valid = false;
> +	struct acpi_device *buddy;
> +	char uid[11];
> +	int err;
> +
> +	memset(&hid, 0, sizeof(hid));
> +	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;
> +	}
> +
> +	err = snprintf(uid, sizeof(uid), "%u",
> +		       tbl_msc->instance_id_linked_device);
> +	if (err >= sizeof(uid)) {

err could be negative error code. This error validation only checks size 
but not error code.

Better to change it to

         if (err < 0 || err >= sizeof(uid))

[SNIP]

Thanks.

-Fenghua