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

[Gavin Shan <gshan@redhat.com>]

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