ACPI/PPTT: Add Processor Properties Topology Table parsing

ACPI 6.2 adds a new table, which describes how processing units
are related to each other in tree like fashion. Caches are
also sprinkled throughout the tree and describe the properties
of the caches in relation to other caches and processing units.

Add the code to parse the cache hierarchy and report the total
number of levels of cache for a given core using
acpi_find_last_cache_level() as well as fill out the individual
cores cache information with cache_setup_acpi() once the
cpu_cacheinfo structure has been populated by the arch specific
code.

An additional patch later in the set adds the ability to report
peers in the topology using find_acpi_cpu_topology()
to report a unique ID for each processing unit at a given level
in the tree. These unique id's can then be used to match related
processing units which exist as threads, within a given
package, etc.
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Vijaya Kumar K <vkilari@codeaurora.org>
Tested-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Tested-by: Tomasz Nowicki <Tomasz.Nowicki@cavium.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

drivers/acpi/pptt.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * pptt.c - parsing of Processor Properties Topology Table (PPTT)
+ *
+ * Copyright (C) 2018, ARM
+ *
+ * This file implements parsing of the Processor Properties Topology Table
+ * which is optionally used to describe the processor and cache topology.
+ * Due to the relative pointers used throughout the table, this doesn't
+ * leverage the existing subtable parsing in the kernel.
+ *
+ * The PPTT structure is an inverted tree, with each node potentially
+ * holding one or two inverted tree data structures describing
+ * the caches available at that level. Each cache structure optionally
+ * contains properties describing the cache at a given level which can be
+ * used to override hardware probed values.
+ */
+#define pr_fmt(fmt) "ACPI PPTT: " fmt
+
+#include <linux/acpi.h>
+#include <linux/cacheinfo.h>
+#include <acpi/processor.h>
+
+static struct acpi_subtable_header *fetch_pptt_subtable(struct acpi_table_header *table_hdr,
+							u32 pptt_ref)
+{
+	struct acpi_subtable_header *entry;
+
+	/* there isn't a subtable at reference 0 */
+	if (pptt_ref < sizeof(struct acpi_subtable_header))
+		return NULL;
+
+	if (pptt_ref + sizeof(struct acpi_subtable_header) > table_hdr->length)
+		return NULL;
+
+	entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr, pptt_ref);
+
+	if (entry->length == 0)
+		return NULL;
+
+	if (pptt_ref + entry->length > table_hdr->length)
+		return NULL;
+
+	return entry;
+}
+
+static struct acpi_pptt_processor *fetch_pptt_node(struct acpi_table_header *table_hdr,
+						   u32 pptt_ref)
+{
+	return (struct acpi_pptt_processor *)fetch_pptt_subtable(table_hdr, pptt_ref);
+}
+
+static struct acpi_pptt_cache *fetch_pptt_cache(struct acpi_table_header *table_hdr,
+						u32 pptt_ref)
+{
+	return (struct acpi_pptt_cache *)fetch_pptt_subtable(table_hdr, pptt_ref);
+}
+
+static struct acpi_subtable_header *acpi_get_pptt_resource(struct acpi_table_header *table_hdr,
+							   struct acpi_pptt_processor *node,
+							   int resource)
+{
+	u32 *ref;
+
+	if (resource >= node->number_of_priv_resources)
+		return NULL;
+
+	ref = ACPI_ADD_PTR(u32, node, sizeof(struct acpi_pptt_processor));
+	ref += resource;
+
+	return fetch_pptt_subtable(table_hdr, *ref);
+}
+
+static inline bool acpi_pptt_match_type(int table_type, int type)
+{
+	return ((table_type & ACPI_PPTT_MASK_CACHE_TYPE) == type ||
+		table_type & ACPI_PPTT_CACHE_TYPE_UNIFIED & type);
+}
+
+/**
+ * acpi_pptt_walk_cache() - Attempt to find the requested acpi_pptt_cache
+ * @table_hdr: Pointer to the head of the PPTT table
+ * @local_level: passed res reflects this cache level
+ * @res: cache resource in the PPTT we want to walk
+ * @found: returns a pointer to the requested level if found
+ * @level: the requested cache level
+ * @type: the requested cache type
+ *
+ * Attempt to find a given cache level, while counting the max number
+ * of cache levels for the cache node.
+ *
+ * Given a pptt resource, verify that it is a cache node, then walk
+ * down each level of caches, counting how many levels are found
+ * as well as checking the cache type (icache, dcache, unified). If a
+ * level & type match, then we set found, and continue the search.
+ * Once the entire cache branch has been walked return its max
+ * depth.
+ *
+ * Return: The cache structure and the level we terminated with.
+ */
+static int acpi_pptt_walk_cache(struct acpi_table_header *table_hdr,
+				int local_level,
+				struct acpi_subtable_header *res,
+				struct acpi_pptt_cache **found,
+				int level, int type)
+{
+	struct acpi_pptt_cache *cache;
+
+	if (res->type != ACPI_PPTT_TYPE_CACHE)
+		return 0;
+
+	cache = (struct acpi_pptt_cache *) res;
+	while (cache) {
+		local_level++;
+
+		if (local_level == level &&
+		    cache->flags & ACPI_PPTT_CACHE_TYPE_VALID &&
+		    acpi_pptt_match_type(cache->attributes, type)) {
+			if (*found != NULL && cache != *found)
+				pr_warn("Found duplicate cache level/type unable to determine uniqueness\n");
+
+			pr_debug("Found cache @ level %d\n", level);
+			*found = cache;
+			/*
+			 * continue looking at this node's resource list
+			 * to verify that we don't find a duplicate
+			 * cache node.
+			 */
+		}
+		cache = fetch_pptt_cache(table_hdr, cache->next_level_of_cache);
+	}
+	return local_level;
+}
+
+static struct acpi_pptt_cache *acpi_find_cache_level(struct acpi_table_header *table_hdr,
+						     struct acpi_pptt_processor *cpu_node,
+						     int *starting_level, int level,
+						     int type)
+{
+	struct acpi_subtable_header *res;
+	int number_of_levels = *starting_level;
+	int resource = 0;
+	struct acpi_pptt_cache *ret = NULL;
+	int local_level;
+
+	/* walk down from processor node */
+	while ((res = acpi_get_pptt_resource(table_hdr, cpu_node, resource))) {
+		resource++;
+
+		local_level = acpi_pptt_walk_cache(table_hdr, *starting_level,
+						   res, &ret, level, type);
+		/*
+		 * we are looking for the max depth. Since its potentially
+		 * possible for a given node to have resources with differing
+		 * depths verify that the depth we have found is the largest.
+		 */
+		if (number_of_levels < local_level)
+			number_of_levels = local_level;
+	}
+	if (number_of_levels > *starting_level)
+		*starting_level = number_of_levels;
+
+	return ret;
+}
+
+/**
+ * acpi_count_levels() - Given a PPTT table, and a cpu node, count the caches
+ * @table_hdr: Pointer to the head of the PPTT table
+ * @cpu_node: processor node we wish to count caches for
+ *
+ * Given a processor node containing a processing unit, walk into it and count
+ * how many levels exist solely for it, and then walk up each level until we hit
+ * the root node (ignore the package level because it may be possible to have
+ * caches that exist across packages). Count the number of cache levels that
+ * exist at each level on the way up.
+ *
+ * Return: Total number of levels found.
+ */
+static int acpi_count_levels(struct acpi_table_header *table_hdr,
+			     struct acpi_pptt_processor *cpu_node)
+{
+	int total_levels = 0;
+
+	do {
+		acpi_find_cache_level(table_hdr, cpu_node, &total_levels, 0, 0);
+		cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent);
+	} while (cpu_node);
+
+	return total_levels;
+}
+
+/**
+ * acpi_pptt_leaf_node() - Given a processor node, determine if its a leaf
+ * @table_hdr: Pointer to the head of the PPTT table
+ * @node: passed node is checked to see if its a leaf
+ *
+ * Determine if the *node parameter is a leaf node by iterating the
+ * PPTT table, looking for nodes which reference it.
+ *
+ * Return: 0 if we find a node referencing the passed node (or table error),
+ * or 1 if we don't.
+ */
+static int acpi_pptt_leaf_node(struct acpi_table_header *table_hdr,
+			       struct acpi_pptt_processor *node)
+{
+	struct acpi_subtable_header *entry;
+	unsigned long table_end;
+	u32 node_entry;
+	struct acpi_pptt_processor *cpu_node;
+	u32 proc_sz;
+
+	table_end = (unsigned long)table_hdr + table_hdr->length;
+	node_entry = ACPI_PTR_DIFF(node, table_hdr);
+	entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr,
+			     sizeof(struct acpi_table_pptt));
+	proc_sz = sizeof(struct acpi_pptt_processor *);
+
+	while ((unsigned long)entry + proc_sz < table_end) {
+		cpu_node = (struct acpi_pptt_processor *)entry;
+		if (entry->type == ACPI_PPTT_TYPE_PROCESSOR &&
+		    cpu_node->parent == node_entry)
+			return 0;
+		if (entry->length == 0)
+			return 0;
+		entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry,
+				     entry->length);
+
+	}
+	return 1;
+}
+
+/**
+ * acpi_find_processor_node() - Given a PPTT table find the requested processor
+ * @table_hdr:  Pointer to the head of the PPTT table
+ * @acpi_cpu_id: cpu we are searching for
+ *
+ * Find the subtable entry describing the provided processor.
+ * This is done by iterating the PPTT table looking for processor nodes
+ * which have an acpi_processor_id that matches the acpi_cpu_id parameter
+ * passed into the function. If we find a node that matches this criteria
+ * we verify that its a leaf node in the topology rather than depending
+ * on the valid flag, which doesn't need to be set for leaf nodes.
+ *
+ * Return: NULL, or the processors acpi_pptt_processor*
+ */
+static struct acpi_pptt_processor *acpi_find_processor_node(struct acpi_table_header *table_hdr,
+							    u32 acpi_cpu_id)
+{
+	struct acpi_subtable_header *entry;
+	unsigned long table_end;
+	struct acpi_pptt_processor *cpu_node;
+	u32 proc_sz;
+
+	table_end = (unsigned long)table_hdr + table_hdr->length;
+	entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr,
+			     sizeof(struct acpi_table_pptt));
+	proc_sz = sizeof(struct acpi_pptt_processor *);
+
+	/* find the processor structure associated with this cpuid */
+	while ((unsigned long)entry + proc_sz < table_end) {
+		cpu_node = (struct acpi_pptt_processor *)entry;
+
+		if (entry->length == 0) {
+			pr_warn("Invalid zero length subtable\n");
+			break;
+		}
+		if (entry->type == ACPI_PPTT_TYPE_PROCESSOR &&
+		    acpi_cpu_id == cpu_node->acpi_processor_id &&
+		     acpi_pptt_leaf_node(table_hdr, cpu_node)) {
+			return (struct acpi_pptt_processor *)entry;
+		}
+
+		entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry,
+				     entry->length);
+	}
+
+	return NULL;
+}
+
+static int acpi_find_cache_levels(struct acpi_table_header *table_hdr,
+				  u32 acpi_cpu_id)
+{
+	int number_of_levels = 0;
+	struct acpi_pptt_processor *cpu;
+
+	cpu = acpi_find_processor_node(table_hdr, acpi_cpu_id);
+	if (cpu)
+		number_of_levels = acpi_count_levels(table_hdr, cpu);
+
+	return number_of_levels;
+}
+
+static u8 acpi_cache_type(enum cache_type type)
+{
+	switch (type) {
+	case CACHE_TYPE_DATA:
+		pr_debug("Looking for data cache\n");
+		return ACPI_PPTT_CACHE_TYPE_DATA;
+	case CACHE_TYPE_INST:
+		pr_debug("Looking for instruction cache\n");
+		return ACPI_PPTT_CACHE_TYPE_INSTR;
+	default:
+	case CACHE_TYPE_UNIFIED:
+		pr_debug("Looking for unified cache\n");
+		/*
+		 * It is important that ACPI_PPTT_CACHE_TYPE_UNIFIED
+		 * contains the bit pattern that will match both
+		 * ACPI unified bit patterns because we use it later
+		 * to match both cases.
+		 */
+		return ACPI_PPTT_CACHE_TYPE_UNIFIED;
+	}
+}
+
+static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *table_hdr,
+						    u32 acpi_cpu_id,
+						    enum cache_type type,
+						    unsigned int level,
+						    struct acpi_pptt_processor **node)
+{
+	int total_levels = 0;
+	struct acpi_pptt_cache *found = NULL;
+	struct acpi_pptt_processor *cpu_node;
+	u8 acpi_type = acpi_cache_type(type);
+
+	pr_debug("Looking for CPU %d's level %d cache type %d\n",
+		 acpi_cpu_id, level, acpi_type);
+
+	cpu_node = acpi_find_processor_node(table_hdr, acpi_cpu_id);
+
+	while (cpu_node && !found) {
+		found = acpi_find_cache_level(table_hdr, cpu_node,
+					      &total_levels, level, acpi_type);
+		*node = cpu_node;
+		cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent);
+	}
+
+	return found;
+}
+
+/* total number of attributes checked by the properties code */
+#define PPTT_CHECKED_ATTRIBUTES 4
+
+/**
+ * update_cache_properties() - Update cacheinfo for the given processor
+ * @this_leaf: Kernel cache info structure being updated
+ * @found_cache: The PPTT node describing this cache instance
+ * @cpu_node: A unique reference to describe this cache instance
+ *
+ * The ACPI spec implies that the fields in the cache structures are used to
+ * extend and correct the information probed from the hardware. Lets only
+ * set fields that we determine are VALID.
+ *
+ * Return: nothing. Side effect of updating the global cacheinfo
+ */
+static void update_cache_properties(struct cacheinfo *this_leaf,
+				    struct acpi_pptt_cache *found_cache,
+				    struct acpi_pptt_processor *cpu_node)
+{
+	int valid_flags = 0;
+
+	this_leaf->fw_token = cpu_node;
+	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID) {
+		this_leaf->size = found_cache->size;
+		valid_flags++;
+	}
+	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID) {
+		this_leaf->coherency_line_size = found_cache->line_size;
+		valid_flags++;
+	}
+	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID) {
+		this_leaf->number_of_sets = found_cache->number_of_sets;
+		valid_flags++;
+	}
+	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID) {
+		this_leaf->ways_of_associativity = found_cache->associativity;
+		valid_flags++;
+	}
+	if (found_cache->flags & ACPI_PPTT_WRITE_POLICY_VALID) {
+		switch (found_cache->attributes & ACPI_PPTT_MASK_WRITE_POLICY) {
+		case ACPI_PPTT_CACHE_POLICY_WT:
+			this_leaf->attributes = CACHE_WRITE_THROUGH;
+			break;
+		case ACPI_PPTT_CACHE_POLICY_WB:
+			this_leaf->attributes = CACHE_WRITE_BACK;
+			break;
+		}
+	}
+	if (found_cache->flags & ACPI_PPTT_ALLOCATION_TYPE_VALID) {
+		switch (found_cache->attributes & ACPI_PPTT_MASK_ALLOCATION_TYPE) {
+		case ACPI_PPTT_CACHE_READ_ALLOCATE:
+			this_leaf->attributes |= CACHE_READ_ALLOCATE;
+			break;
+		case ACPI_PPTT_CACHE_WRITE_ALLOCATE:
+			this_leaf->attributes |= CACHE_WRITE_ALLOCATE;
+			break;
+		case ACPI_PPTT_CACHE_RW_ALLOCATE:
+		case ACPI_PPTT_CACHE_RW_ALLOCATE_ALT:
+			this_leaf->attributes |=
+				CACHE_READ_ALLOCATE | CACHE_WRITE_ALLOCATE;
+			break;
+		}
+	}
+	/*
+	 * If the above flags are valid, and the cache type is NOCACHE
+	 * update the cache type as well.
+	 */
+	if (this_leaf->type == CACHE_TYPE_NOCACHE &&
+	    valid_flags == PPTT_CHECKED_ATTRIBUTES)
+		this_leaf->type = CACHE_TYPE_UNIFIED;
+}
+
+static void cache_setup_acpi_cpu(struct acpi_table_header *table,
+				 unsigned int cpu)
+{
+	struct acpi_pptt_cache *found_cache;
+	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
+	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	struct cacheinfo *this_leaf;
+	unsigned int index = 0;
+	struct acpi_pptt_processor *cpu_node = NULL;
+
+	while (index < get_cpu_cacheinfo(cpu)->num_leaves) {
+		this_leaf = this_cpu_ci->info_list + index;
+		found_cache = acpi_find_cache_node(table, acpi_cpu_id,
+						   this_leaf->type,
+						   this_leaf->level,
+						   &cpu_node);
+		pr_debug("found = %p %p\n", found_cache, cpu_node);
+		if (found_cache)
+			update_cache_properties(this_leaf,
+						found_cache,
+						cpu_node);
+
+		index++;
+	}
+}
+
+/* Passing level values greater than this will result in search termination */
+#define PPTT_ABORT_PACKAGE 0xFF
+
+static struct acpi_pptt_processor *acpi_find_processor_package_id(struct acpi_table_header *table_hdr,
+								  struct acpi_pptt_processor *cpu,
+								  int level, int flag)
+{
+	struct acpi_pptt_processor *prev_node;
+
+	while (cpu && level) {
+		if (cpu->flags & flag)
+			break;
+		pr_debug("level %d\n", level);
+		prev_node = fetch_pptt_node(table_hdr, cpu->parent);
+		if (prev_node == NULL)
+			break;
+		cpu = prev_node;
+		level--;
+	}
+	return cpu;
+}
+
+/**
+ * topology_get_acpi_cpu_tag() - Find a unique topology value for a feature
+ * @table: Pointer to the head of the PPTT table
+ * @cpu: Kernel logical cpu number
+ * @level: A level that terminates the search
+ * @flag: A flag which terminates the search
+ *
+ * Get a unique value given a cpu, and a topology level, that can be
+ * matched to determine which cpus share common topological features
+ * at that level.
+ *
+ * Return: Unique value, or -ENOENT if unable to locate cpu
+ */
+static int topology_get_acpi_cpu_tag(struct acpi_table_header *table,
+				     unsigned int cpu, int level, int flag)
+{
+	struct acpi_pptt_processor *cpu_node;
+	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+
+	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
+	if (cpu_node) {
+		cpu_node = acpi_find_processor_package_id(table, cpu_node,
+							  level, flag);
+		/* Only the first level has a guaranteed id */
+		if (level == 0)
+			return cpu_node->acpi_processor_id;
+		return ACPI_PTR_DIFF(cpu_node, table);
+	}
+	pr_warn_once("PPTT table found, but unable to locate core %d (%d)\n",
+		    cpu, acpi_cpu_id);
+	return -ENOENT;
+}
+
+static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
+{
+	struct acpi_table_header *table;
+	acpi_status status;
+	int retval;
+
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
+	if (ACPI_FAILURE(status)) {
+		pr_warn_once("No PPTT table found, cpu topology may be inaccurate\n");
+		return -ENOENT;
+	}
+	retval = topology_get_acpi_cpu_tag(table, cpu, level, flag);
+	pr_debug("Topology Setup ACPI cpu %d, level %d ret = %d\n",
+		 cpu, level, retval);
+	acpi_put_table(table);
+
+	return retval;
+}
+
+/**
+ * acpi_find_last_cache_level() - Determines the number of cache levels for a PE
+ * @cpu: Kernel logical cpu number
+ *
+ * Given a logical cpu number, returns the number of levels of cache represented
+ * in the PPTT. Errors caused by lack of a PPTT table, or otherwise, return 0
+ * indicating we didn't find any cache levels.
+ *
+ * Return: Cache levels visible to this core.
+ */
+int acpi_find_last_cache_level(unsigned int cpu)
+{
+	u32 acpi_cpu_id;
+	struct acpi_table_header *table;
+	int number_of_levels = 0;
+	acpi_status status;
+
+	pr_debug("Cache Setup find last level cpu=%d\n", cpu);
+
+	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
+	if (ACPI_FAILURE(status)) {
+		pr_warn_once("No PPTT table found, cache topology may be inaccurate\n");
+	} else {
+		number_of_levels = acpi_find_cache_levels(table, acpi_cpu_id);
+		acpi_put_table(table);
+	}
+	pr_debug("Cache Setup find last level level=%d\n", number_of_levels);
+
+	return number_of_levels;
+}
+
+/**
+ * cache_setup_acpi() - Override CPU cache topology with data from the PPTT
+ * @cpu: Kernel logical cpu number
+ *
+ * Updates the global cache info provided by cpu_get_cacheinfo()
+ * when there are valid properties in the acpi_pptt_cache nodes. A
+ * successful parse may not result in any updates if none of the
+ * cache levels have any valid flags set.  Futher, a unique value is
+ * associated with each known CPU cache entry. This unique value
+ * can be used to determine whether caches are shared between cpus.
+ *
+ * Return: -ENOENT on failure to find table, or 0 on success
+ */
+int cache_setup_acpi(unsigned int cpu)
+{
+	struct acpi_table_header *table;
+	acpi_status status;
+
+	pr_debug("Cache Setup ACPI cpu %d\n", cpu);
+
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
+	if (ACPI_FAILURE(status)) {
+		pr_warn_once("No PPTT table found, cache topology may be inaccurate\n");
+		return -ENOENT;
+	}
+
+	cache_setup_acpi_cpu(table, cpu);
+	acpi_put_table(table);
+
+	return status;
+}
+
+/**
+ * find_acpi_cpu_topology() - Determine a unique topology value for a given cpu
+ * @cpu: Kernel logical cpu number
+ * @level: The topological level for which we would like a unique ID
+ *
+ * Determine a topology unique ID for each thread/core/cluster/mc_grouping
+ * /socket/etc. This ID can then be used to group peers, which will have
+ * matching ids.
+ *
+ * The search terminates when either the requested level is found or
+ * we reach a root node. Levels beyond the termination point will return the
+ * same unique ID. The unique id for level 0 is the acpi processor id. All
+ * other levels beyond this use a generated value to uniquely identify
+ * a topological feature.
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, or the cpu cannot be found.
+ * Otherwise returns a value which represents a unique topological feature.
+ */
+int find_acpi_cpu_topology(unsigned int cpu, int level)
+{
+	return find_acpi_cpu_topology_tag(cpu, level, 0);
+}
+
+/**
+ * find_acpi_cpu_cache_topology() - Determine a unique cache topology value
+ * @cpu: Kernel logical cpu number
+ * @level: The cache level for which we would like a unique ID
+ *
+ * Determine a unique ID for each unified cache in the system
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, or the cpu cannot be found.
+ * Otherwise returns a value which represents a unique topological feature.
+ */
+int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
+{
+	struct acpi_table_header *table;
+	struct acpi_pptt_cache *found_cache;
+	acpi_status status;
+	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	struct acpi_pptt_processor *cpu_node = NULL;
+	int ret = -1;
+
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
+	if (ACPI_FAILURE(status)) {
+		pr_warn_once("No PPTT table found, topology may be inaccurate\n");
+		return -ENOENT;
+	}
+
+	found_cache = acpi_find_cache_node(table, acpi_cpu_id,
+					   CACHE_TYPE_UNIFIED,
+					   level,
+					   &cpu_node);
+	if (found_cache)
+		ret = ACPI_PTR_DIFF(cpu_node, table);
+
+	acpi_put_table(table);
+
+	return ret;
+}
+
+
+/**
+ * find_acpi_cpu_topology_package() - Determine a unique cpu package value
+ * @cpu: Kernel logical cpu number
+ *
+ * Determine a topology unique package ID for the given cpu.
+ * This ID can then be used to group peers, which will have matching ids.
+ *
+ * The search terminates when either a level is found with the PHYSICAL_PACKAGE
+ * flag set or we reach a root node.
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, or the cpu cannot be found.
+ * Otherwise returns a value which represents the package for this cpu.
+ */
+int find_acpi_cpu_topology_package(unsigned int cpu)
+{
+	return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
+					  ACPI_PPTT_PHYSICAL_PACKAGE);
+}

include/linux/acpi.h

@@ -1297,4 +1297,8 @@ static inline int lpit_read_residency_count_address(u64 *address)
 }
 #endif
 
+int find_acpi_cpu_topology(unsigned int cpu, int level);
+int find_acpi_cpu_topology_package(unsigned int cpu);
+int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
+
 #endif	/*_LINUX_ACPI_H*/