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SubjectRe: [PATCH v4 2/9] ACPI/PPTT: Add Processor Properties Topology Table parsing
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Hi,

On 11/15/2017 03:27 AM, Xiongfeng Wang wrote:
> Hi Jeremy,
>
> On 2017/11/10 5:03, Jeremy Linton wrote:
>> 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.
>>
>> Further, report peers in the topology using setup_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, COD (clusters
>> on die), within a given package, etc.
>>
>> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
>> ---
>> drivers/acpi/pptt.c | 452 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 452 insertions(+)
>> create mode 100644 drivers/acpi/pptt.c
>>
>> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
>> new file mode 100644
>> index 000000000000..9c9b8b4660e0
>> --- /dev/null
>> +++ b/drivers/acpi/pptt.c
>> @@ -0,0 +1,452 @@
>> +/*
>> + * Copyright (C) 2017, ARM
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
>> + * more details.
>> + *
>> + * This file implements parsing of Processor Properties Topology Table (PPTT)
>> + * 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 that 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>
>> +
>> +/*
>> + * Given the PPTT table, find and verify that the subtable entry
>> + * is located within the table
>> + */
>> +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 (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);
>> +}
>> +
>> +/*
>> + * 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.
>> + */
>> +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) &&
>> + ((cache->attributes & ACPI_PPTT_MASK_CACHE_TYPE) == type)) {
>> + if ((*found != NULL) && (cache != *found))
>> + pr_err("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;
>> +}
>> +
>> +/*
>> + * Given a CPU node look for cache levels that exist at this level, and then
>> + * for each cache node, count how many levels exist below (logically above) it.
>> + * If a level and type are specified, and we find that level/type, abort
>> + * processing and return the acpi_pptt_cache structure.
>> + */
>> +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;
>> +}
>> +
>> +/*
>> + * 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.
>> + */
>> +static int acpi_process_node(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;
>> +}
>> +
>> +/*
>> + * 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 refrencing the passed node,
>> + * 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;
>> +
>> + 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));
>> +
>> + while ((unsigned long)(entry + 1) < table_end) {
>> + cpu_node = (struct acpi_pptt_processor *)entry;
>> + if ((entry->type == ACPI_PPTT_TYPE_PROCESSOR) &&
>> + (cpu_node->parent == node_entry))
>> + return 0;
>> + entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry,
>> + entry->length);
>> + }
>> + return 1;
>> +}
>> +
>> +/*
>> + * 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.
>> + */
>> +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;
>> +
>> + table_end = (unsigned long)table_hdr + table_hdr->length;
>> + entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr,
>> + sizeof(struct acpi_table_pptt));
>> +
>> + /* find the processor structure associated with this cpuid */
>> + while ((unsigned long)(entry + 1) < table_end) {
>> + cpu_node = (struct acpi_pptt_processor *)entry;
>> +
>> + if (entry->length == 0) {
>> + pr_err("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_process_node(table_hdr, cpu);
>> +
>> + return number_of_levels;
>> +}
>> +
>> +/* Convert the linux cache_type to a ACPI PPTT cache type value */
>> +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;
>> + }
>> +}
>> +
>> +/* find the ACPI node describing the cache type/level for the given CPU */
>> +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;
>> +}
>> +
>> +/*
>> + * The ACPI spec implies that the fields in the cache structures are used to
>> + * extend and correct the information probed from the hardware. In the case
>> + * of arm64 the CCSIDR probing has been removed because it might be incorrect.
>> + */
>> +static void update_cache_properties(struct cacheinfo *this_leaf,
>> + struct acpi_pptt_cache *found_cache,
>> + struct acpi_pptt_processor *cpu_node)
>> +{
>> + if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID)
>> + this_leaf->size = found_cache->size;
>> + if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID)
>> + this_leaf->coherency_line_size = found_cache->line_size;
>> + if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID)
>> + this_leaf->number_of_sets = found_cache->number_of_sets;
>> + if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID)
>> + this_leaf->ways_of_associativity = found_cache->associativity;
>> + 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;
>> + }
>> +}
>> +
>

First, thanks for testing this!

> I test this patch on our platform, and the result is that 'type' property of L3Cache
> is not displayed.
>
> So I add some print to debug, and found out that ARM64 __populate_cache_leaves()
> set this_cpu_ci->info_list[L3Cache_level].type to 0, bacause we can't get the type of
> L3Cache from CLIDR.
>
> Then cache_setup_acpi_cpu() try to find L3Cache from PPTT. Because L3Cache type read from
> CLIDR is 0, so branch in acpi_cache_type falls into default: ACPI_PPTT_CACHE_TYPE_UNIFIED.
> So we can find L3Cache in PPTT, then use update_cache_properties() to update L3Cache property.
> But update_cache_properties() doesn't update the cache type, so this_cpu_ci->info_list[L3Cache_level].type
> is still 0, cache_default_attrs_is_visible() returns 0, and 'type' property of L3Cache won't be displayed in sysfs.

Oh, right! The other implication is that you can't add caches which
aren't unified if they aren't detected by the cache description registers.

>
> Can we set this_cpu_ci->info_list[level].type to CACHE_TYPE_UNIFIED in __populate_cache_leaves() when level >= 3 ?
> Or can we update cache type property in update_cache_properties() ?

Sure, I think maybe updating it here in update_cache_properties is a
better plan if we can assure that enough of the fields are valid that we
aren't just displaying a zero size cache in sysfs..

>
>
> Thanks,
> Xiongfeng Wang
>
>
>> +/*
>> + * Update the kernel cache information for each level of cache
>> + * associated with the given acpi cpu.
>> + */
>> +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++;
>> + }
>> +}
>> +
>> +/**
>> + * 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_err_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_err_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;
>> +}
>>
>

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