Re: [PATCH 03/33] ACPI / PPTT: Add acpi_pptt_cache_v1_full to use pptt cache as one structure

Gavin Shan
2025-11-08T04:55:05Z

Hi Ben,

On 11/7/25 10:34 PM, Ben Horgan wrote:
> In actbl2.h, struct acpi_pptt_cache describes the fields in the original
> cache type structure. In PPTT table version 3 a new field was added at the
> end, cache_id. This is described in struct acpi_pptt_cache_v1. Introduce
> the new, acpi_pptt_cache_v1_full to contain both these structures. Update
> the existing code to use this new struct. This simplifies the code, removes
> a non-standard use of ACPI_ADD_PTR and allows using the length in the
> header to check if the cache_id is valid.
>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
> Changes since v3:
> New patch
> ---
> drivers/acpi/pptt.c | 104 ++++++++++++++++++++++++--------------------
> 1 file changed, 58 insertions(+), 46 deletions(-)
>

Two nitpicks below. LGTM in either way.

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 1027ca3566b1..1ed2099c0d1a 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -21,6 +21,11 @@
> #include <linux/cacheinfo.h>
> #include <acpi/processor.h>
>
> +struct acpi_pptt_cache_v1_full {
> + struct acpi_pptt_cache f;
> + struct acpi_pptt_cache_v1 extra;
> +} __packed;
> +
> static struct acpi_subtable_header *fetch_pptt_subtable(struct acpi_table_header *table_hdr,
> u32 pptt_ref)
> {
> @@ -50,10 +55,24 @@ static struct acpi_pptt_processor *fetch_pptt_node(struct acpi_table_header *tab
> 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)
> +static struct acpi_pptt_cache_v1_full *fetch_pptt_cache(struct acpi_table_header *table_hdr,
> + u32 pptt_ref)
> {
> - return (struct acpi_pptt_cache *)fetch_pptt_subtable(table_hdr, pptt_ref);
> + return (struct acpi_pptt_cache_v1_full *)fetch_pptt_subtable(table_hdr, pptt_ref);
> +}
> +
> +#define ACPI_PPTT_CACHE_V1_LEN sizeof(struct acpi_pptt_cache_v1_full)
> +
> +/*
> + * From PPTT table version 3, a new field cache_id was added at the end of
> + * the cache type structure. We now use struct acpi_pptt_cache_v1_full,
> + * containing the cache_id, everywhere but must check validity before accessing
> + * the cache_id.
> + */
> +static bool acpi_pptt_cache_id_is_valid(struct acpi_pptt_cache_v1_full *cache)
> +{
> + return (cache->f.header.length >= ACPI_PPTT_CACHE_V1_LEN &&
> + cache->f.flags & ACPI_PPTT_CACHE_ID_VALID);
> }
>

This function is nice fit to 'inline'. Besides, I'm not sure if we can just
use sizeof(*cache) instead of ACPI_PPTT_CACHE_V1_LEN, which is used for once
in pptt.c

> static struct acpi_subtable_header *acpi_get_pptt_resource(struct acpi_table_header *table_hdr,
> @@ -103,30 +122,30 @@ static unsigned int acpi_pptt_walk_cache(struct acpi_table_header *table_hdr,
> unsigned int local_level,
> unsigned int *split_levels,
> struct acpi_subtable_header *res,
> - struct acpi_pptt_cache **found,
> + struct acpi_pptt_cache_v1_full **found,
> unsigned int level, int type)
> {
> - struct acpi_pptt_cache *cache;
> + struct acpi_pptt_cache_v1_full *cache;
>
> if (res->type != ACPI_PPTT_TYPE_CACHE)
> return 0;
>
> - cache = (struct acpi_pptt_cache *) res;
> + cache = (struct acpi_pptt_cache_v1_full *)res;
> while (cache) {
> local_level++;
>
> - if (!(cache->flags & ACPI_PPTT_CACHE_TYPE_VALID)) {
> - cache = fetch_pptt_cache(table_hdr, cache->next_level_of_cache);
> + if (!(cache->f.flags & ACPI_PPTT_CACHE_TYPE_VALID)) {
> + cache = fetch_pptt_cache(table_hdr, cache->f.next_level_of_cache);
> continue;
> }
>
> if (split_levels &&
> - (acpi_pptt_match_type(cache->attributes, ACPI_PPTT_CACHE_TYPE_DATA) ||
> - acpi_pptt_match_type(cache->attributes, ACPI_PPTT_CACHE_TYPE_INSTR)))
> + (acpi_pptt_match_type(cache->f.attributes, ACPI_PPTT_CACHE_TYPE_DATA) ||
> + acpi_pptt_match_type(cache->f.attributes, ACPI_PPTT_CACHE_TYPE_INSTR)))
> *split_levels = local_level;
>
> if (local_level == level &&
> - acpi_pptt_match_type(cache->attributes, type)) {
> + acpi_pptt_match_type(cache->f.attributes, type)) {
> if (*found != NULL && cache != *found)
> pr_warn("Found duplicate cache level/type unable to determine uniqueness\n");
>
> @@ -138,12 +157,12 @@ static unsigned int acpi_pptt_walk_cache(struct acpi_table_header *table_hdr,
> * cache node.
> */
> }
> - cache = fetch_pptt_cache(table_hdr, cache->next_level_of_cache);
> + cache = fetch_pptt_cache(table_hdr, cache->f.next_level_of_cache);
> }
> return local_level;
> }
>
> -static struct acpi_pptt_cache *
> +static struct acpi_pptt_cache_v1_full *
> acpi_find_cache_level(struct acpi_table_header *table_hdr,
> struct acpi_pptt_processor *cpu_node,
> unsigned int *starting_level, unsigned int *split_levels,
> @@ -152,7 +171,7 @@ acpi_find_cache_level(struct acpi_table_header *table_hdr,
> struct acpi_subtable_header *res;
> unsigned int number_of_levels = *starting_level;
> int resource = 0;
> - struct acpi_pptt_cache *ret = NULL;
> + struct acpi_pptt_cache_v1_full *ret = NULL;
> unsigned int local_level;
>
> /* walk down from processor node */
> @@ -324,14 +343,14 @@ static u8 acpi_cache_type(enum cache_type type)
> }
> }
>
> -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)
> +static struct acpi_pptt_cache_v1_full *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)
> {
> unsigned int total_levels = 0;
> - struct acpi_pptt_cache *found = NULL;
> + struct acpi_pptt_cache_v1_full *found = NULL;
> struct acpi_pptt_processor *cpu_node;
> u8 acpi_type = acpi_cache_type(type);
>
> @@ -355,7 +374,6 @@ static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *ta
> * @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
> - * @revision: The revision of the PPTT table
> *
> * 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
> @@ -364,23 +382,20 @@ static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *ta
> * 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,
> - u8 revision)
> + struct acpi_pptt_cache_v1_full *found_cache,
> + struct acpi_pptt_processor *cpu_node)
> {
> - struct acpi_pptt_cache_v1* found_cache_v1;
> -
> this_leaf->fw_token = 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) {
> + if (found_cache->f.flags & ACPI_PPTT_SIZE_PROPERTY_VALID)
> + this_leaf->size = found_cache->f.size;
> + if (found_cache->f.flags & ACPI_PPTT_LINE_SIZE_VALID)
> + this_leaf->coherency_line_size = found_cache->f.line_size;
> + if (found_cache->f.flags & ACPI_PPTT_NUMBER_OF_SETS_VALID)
> + this_leaf->number_of_sets = found_cache->f.number_of_sets;
> + if (found_cache->f.flags & ACPI_PPTT_ASSOCIATIVITY_VALID)
> + this_leaf->ways_of_associativity = found_cache->f.associativity;
> + if (found_cache->f.flags & ACPI_PPTT_WRITE_POLICY_VALID) {
> + switch (found_cache->f.attributes & ACPI_PPTT_MASK_WRITE_POLICY) {
> case ACPI_PPTT_CACHE_POLICY_WT:
> this_leaf->attributes = CACHE_WRITE_THROUGH;
> break;
> @@ -389,8 +404,8 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
> break;
> }
> }
> - if (found_cache->flags & ACPI_PPTT_ALLOCATION_TYPE_VALID) {
> - switch (found_cache->attributes & ACPI_PPTT_MASK_ALLOCATION_TYPE) {
> + if (found_cache->f.flags & ACPI_PPTT_ALLOCATION_TYPE_VALID) {
> + switch (found_cache->f.attributes & ACPI_PPTT_MASK_ALLOCATION_TYPE) {
> case ACPI_PPTT_CACHE_READ_ALLOCATE:
> this_leaf->attributes |= CACHE_READ_ALLOCATE;
> break;
> @@ -415,13 +430,11 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
> * specified in PPTT.
> */
> if (this_leaf->type == CACHE_TYPE_NOCACHE &&
> - found_cache->flags & ACPI_PPTT_CACHE_TYPE_VALID)
> + found_cache->f.flags & ACPI_PPTT_CACHE_TYPE_VALID)
> this_leaf->type = CACHE_TYPE_UNIFIED;
>
> - if (revision >= 3 && (found_cache->flags & ACPI_PPTT_CACHE_ID_VALID)) {
> - found_cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> - found_cache, sizeof(struct acpi_pptt_cache));
> - this_leaf->id = found_cache_v1->cache_id;
> + if (acpi_pptt_cache_id_is_valid(found_cache)) {
> + this_leaf->id = found_cache->extra.cache_id;
> this_leaf->attributes |= CACHE_ID;
> }
> }
> @@ -429,7 +442,7 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
> static void cache_setup_acpi_cpu(struct acpi_table_header *table,
> unsigned int cpu)
> {
> - struct acpi_pptt_cache *found_cache;
> + struct acpi_pptt_cache_v1_full *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;
> @@ -445,8 +458,7 @@ static void cache_setup_acpi_cpu(struct acpi_table_header *table,
> pr_debug("found = %p %p\n", found_cache, cpu_node);
> if (found_cache)
> update_cache_properties(this_leaf, found_cache,
> - ACPI_TO_POINTER(ACPI_PTR_DIFF(cpu_node, table)),
> - table->revision);
> + ACPI_TO_POINTER(ACPI_PTR_DIFF(cpu_node, table)));
>
> index++;
> }

Thanks,
Gavin