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SubjectRe: [PATCH v3 1/7] ACPI/PPTT: Add Processor Properties Topology Table parsing
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Hi Jeremy,

Please see below some suggestions.

On 12/10/17 20:48, 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 | 485 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 485 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..c86715fed4a7
> --- /dev/null
> +++ b/drivers/acpi/pptt.c
> @@ -0,1 +1,485 @@
> +/*
> + * 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.
> + */
> +#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)
> + return NULL;

Seeing the usage of pptt_ref to retrieve the subtable, would the
following be a more accurate check?

if (pptt_ref < sizeof(struct acpi_table_header))
return NULL;

> +
> + if (pptt_ref + sizeof(struct acpi_subtable_header) > table_hdr->length)
> + return NULL;
> +
> + entry = (struct acpi_subtable_header *)((u8 *)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 = *(u32 *)((u8 *)node + sizeof(struct acpi_pptt_processor) +
> + sizeof(u32) * resource);
> +

I think this can be simplified as:

ref = *((u32 *)(node + 1) + resource);

> + return fetch_pptt_subtable(table_hdr, ref);
> +}
> +
> +/*
> + * 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)
> + 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 the 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 given node is a leaf node */
> +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;

Can cpu_node be defined inside the loop? It isn't used outside.

> +
> + table_end = (unsigned long)table_hdr + table_hdr->length;
> + node_entry = (u32)((u8 *)node - (u8 *)table_hdr);
> + entry = (struct acpi_subtable_header *)((u8 *)table_hdr +
> + sizeof(struct acpi_table_pptt));
> +
> + while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) < table_end) {

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 = (struct acpi_subtable_header *)((u8 *)entry + entry->length);
> + }
> + return 1;
> +}
> +
> +/*
> + * Find the subtable entry describing the provided 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;
> +
> + table_end = (unsigned long)table_hdr + table_hdr->length;
> + entry = (struct acpi_subtable_header *)((u8 *)table_hdr +
> + sizeof(struct acpi_table_pptt));

Can I suggest having two inline functions for this and the above function?

static inline unsigned long acpi_get_table_end(const struct
acpi_table_header *);

static inline struct acpi_subtable_header *acpi_get_first_entry(const
struct acpi_table_header *);

(Feel free to adapt the names of course)

> +
> + /* find the processor structure associated with this cpuid */
> + while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) < table_end) {

Same as above -> (unsigned long) (entry + 1).


> + cpu_node = (struct acpi_pptt_processor *)entry;
> +
> + if ((entry->type == ACPI_PPTT_TYPE_PROCESSOR) &&
> + acpi_pptt_leaf_node(table_hdr, cpu_node)) {
> + pr_debug("checking phy_cpu_id %d against acpi id %d\n",
> + acpi_cpu_id, cpu_node->acpi_processor_id);
> + if (acpi_cpu_id == cpu_node->acpi_processor_id) {
> + /* found the correct entry */
> + pr_debug("match found!\n");
> + return (struct acpi_pptt_processor *)entry;
> + }
> + }
> +
> + if (entry->length == 0) {
> + pr_err("Invalid zero length subtable\n");
> + break;
> + }
> + entry = (struct acpi_subtable_header *)
> + ((u8 *)entry + entry->length);


I also think it would be nicer to have an inline function for this:

static struct acpi_subtable_header *acpi_get_next_entry(const struct
acpi_subtable_header *);


> + }
> +
> + return NULL;
> +}
> +
> +/*
> + * Given a acpi_pptt_processor node, walk up until we identify the
> + * package that the node is associated with or we run out of levels
> + * to request.
> + */
> +static struct acpi_pptt_processor *acpi_find_processor_package_id(
> + struct acpi_table_header *table_hdr,
> + struct acpi_pptt_processor *cpu,
> + int level)
> +{
> + struct acpi_pptt_processor *prev_node;
> +
> + while (cpu && level && !(cpu->flags & ACPI_PPTT_PHYSICAL_PACKAGE)) {
> + 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;
> +}
> +
> +static int acpi_parse_pptt(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;
> +}
> +
> +#define ACPI_6_2_CACHE_TYPE_DATA (0x0)
> +#define ACPI_6_2_CACHE_TYPE_INSTR (1<<2)
> +#define ACPI_6_2_CACHE_TYPE_UNIFIED (1<<3)
> +#define ACPI_6_2_CACHE_POLICY_WB (0x0)
> +#define ACPI_6_2_CACHE_POLICY_WT (1<<4)
> +#define ACPI_6_2_CACHE_READ_ALLOCATE (0x0)
> +#define ACPI_6_2_CACHE_WRITE_ALLOCATE (0x01)
> +#define ACPI_6_2_CACHE_RW_ALLOCATE (0x02)
> +
> +static u8 acpi_cache_type(enum cache_type type)
> +{
> + switch (type) {
> + case CACHE_TYPE_DATA:
> + pr_debug("Looking for data cache\n");
> + return ACPI_6_2_CACHE_TYPE_DATA;
> + case CACHE_TYPE_INST:
> + pr_debug("Looking for instruction cache\n");
> + return ACPI_6_2_CACHE_TYPE_INSTR;
> + default:
> + pr_debug("Unknown cache type, assume unified\n");
> + case CACHE_TYPE_UNIFIED:
> + pr_debug("Looking for unified cache\n");
> + return ACPI_6_2_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);
> + if (!cpu_node)
> + return NULL;
> +
> + do {
> + 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);
> + } while ((cpu_node) && (!found));

Why not combine the do...while loop and the pevious check in a simple
while loop? The same condion should work as such for a while loop.

Cheers,

--
Julien Thierry

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