Commit 6b585f4c authored by Rob Herring's avatar Rob Herring Committed by Greg Kroah-Hartman
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cacheinfo: Set cache 'id' based on DT data 

Use the minimum CPU h/w id of the CPUs associated with the cache for the
cache 'id'. This will provide a stable id value for a given system. As
we need to check all possible CPUs, we can't use the shared_cpu_map
which is just online CPUs. As there's not a cache to CPUs mapping in DT,
we have to walk all CPU nodes and then walk cache levels.

The cache_id exposed to user-space has historically been 32 bits, and
is too late to change. This value is parsed into a u32 by user-space
libraries such as libvirt:
https://github.com/libvirt/libvirt/blob/master/src/util/virresctrl.c#L1588



Give up on assigning cache-id's if a CPU h/w id greater than 32 bits
is found.

match_cache_node() does not make use of the __free() cleanup helpers
because of_find_next_cache_node(prev) does not drop a reference to prev,
and its too easy to accidentally drop the reference on cpu, which belongs
to for_each_of_cpu_node().

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: default avatarRob Herring <robh@kernel.org>
[ ben: converted to use the __free cleanup idiom ]
Signed-off-by: default avatarBen Horgan <ben.horgan@arm.com>
[ morse: Add checks to give up if a value larger than 32 bits is seen. ]
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Reviewed-by: default avatarJonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: default avatarGavin Shan <gshan@redhat.com>
Link: https://lore.kernel.org/r/20250711182743.30141-2-james.morse@arm.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 35cff7af

drivers/base/cacheinfo.c

+45 −0
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt



#include <linux/acpi.h>

#include <linux/bitfield.h>

#include <linux/bitops.h>

#include <linux/cacheinfo.h>

#include <linux/compiler.h>
@@ -183,6 +184,49 @@ static bool cache_node_is_unified(struct cacheinfo *this_leaf, 
	return of_property_read_bool(np, "cache-unified");

}



static bool match_cache_node(struct device_node *cpu,

			     const struct device_node *cache_node)

{

	struct device_node *prev, *cache = of_find_next_cache_node(cpu);



	while (cache) {

		if (cache == cache_node) {

			of_node_put(cache);

			return true;

		}



		prev = cache;

		cache = of_find_next_cache_node(cache);

		of_node_put(prev);

	}



	return false;

}



static void cache_of_set_id(struct cacheinfo *this_leaf,

			    struct device_node *cache_node)

{

	struct device_node *cpu;

	u32 min_id = ~0;



	for_each_of_cpu_node(cpu) {

		u64 id = of_get_cpu_hwid(cpu, 0);



		if (FIELD_GET(GENMASK_ULL(63, 32), id)) {

			of_node_put(cpu);

			return;

		}



		if (match_cache_node(cpu, cache_node))

			min_id = min(min_id, id);

	}



	if (min_id != ~0) {

		this_leaf->id = min_id;

		this_leaf->attributes |= CACHE_ID;

	}

}



static void cache_of_set_props(struct cacheinfo *this_leaf,

			       struct device_node *np)

{
@@ -198,6 +242,7 @@ static void cache_of_set_props(struct cacheinfo *this_leaf, 
	cache_get_line_size(this_leaf, np);

	cache_nr_sets(this_leaf, np);

	cache_associativity(this_leaf);

	cache_of_set_id(this_leaf, np);

}



static int cache_setup_of_node(unsigned int cpu)