Message-ID: <0e61514a-576e-794e-c8e7-0f42e676eb55@arm.com>
Date:   Fri, 13 Oct 2017 17:41:00 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     Julien Thierry <julien.thierry@....com>, linux-acpi@...r.kernel.org
Cc:     mark.rutland@....com, Jonathan.Zhang@...ium.com,
        Jayachandran.Nair@...ium.com, lorenzo.pieralisi@....com,
        catalin.marinas@....com, gregkh@...uxfoundation.org,
        jhugo@...eaurora.org, rjw@...ysocki.net, linux-pm@...r.kernel.org,
        will.deacon@....com, linux-kernel@...r.kernel.org, ahs3@...hat.com,
        viresh.kumar@...aro.org, hanjun.guo@...aro.org,
        sudeep.holla@....com, austinwc@...eaurora.org,
        wangxiongfeng2@...wei.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/7] ACPI/PPTT: Add Processor Properties Topology Table
 parsing

Hi,


Thanks for spending the time to take a look at this.


On 10/13/2017 04:56 AM, Julien Thierry wrote:
> 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@....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;

Yes, that makes it better match the comment, and I guess tightens up the 
sanity checking. The original intention was just to catch null 
references that were encoded as parent/etc fields.

> 
>> +
>> +    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);

I think Thomasz had a better suggestion with regard to ACPI_ADD_PTR() 
for avoiding the explicit pointer math, although it may not be that 
clean either because it doesn't fit 1:1 with the macro at the moment, 
maybe i'm doing it wrong...

> 
>> +    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.

Yes, but i'm not sure that is the style of the acpi code, if you look at 
scan.c, acpi_ipmi.c maybe others, they seem to be following the "all 
definitions at the top of the block" form despite having a few loops 
with variables that are only used in the block.

> 
>> +
>> +    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 *);

Which is a bit overkill for an add, let me think about this one.

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

This one and the below are really just degenerate cases of 
fetch_pptt_subtable().

> 
> (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 *);

Which is just a degenerate case of fetch_pptt_subtable() in both cases 
after having had the macro in actypes.h pointed out, I think most of 
this manipulation is going to just get buried behind those macros.


> 
> 
>> +    }
>> +
>> +    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.

Ok, sure...

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