[PATCH] cacheinfo: Introduce cache id

[Fenghua Yu]

From: Fenghua Yu <fenghua.yu@xxxxxxxxx>

Each cache node is described by cacheinfo and is a unique node across
the platform. But there is no id for a cache node. We introduce cache ID
to identify a cache node.

Intel Cache Allocation Technology (CAT) allows some control on the
allocation policy within each cache that it controls. We need a unique
cache ID for each cache level to allow the user to specify which
controls are applied to which cache.

The cache id is first enabled on x86. It can be enabled on other platforms
as well. The cache id is not necessary contiguous.

Add an "id" entry to /sys/devices/system/cpu/cpu*/cache/index*/

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
 arch/x86/kernel/cpu/intel_cacheinfo.c | 21 +++++++++++++++++++++
 drivers/base/cacheinfo.c              |  5 +++++
 include/linux/cacheinfo.h             |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index de6626c..aefc1e5 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -153,6 +153,7 @@ struct _cpuid4_info_regs {
 	union _cpuid4_leaf_eax eax;
 	union _cpuid4_leaf_ebx ebx;
 	union _cpuid4_leaf_ecx ecx;
+	unsigned int id;
 	unsigned long size;
 	struct amd_northbridge *nb;
 };
@@ -894,6 +895,9 @@ static void __cache_cpumap_setup(unsigned int cpu, int index,
 static void ci_leaf_init(struct cacheinfo *this_leaf,
 			 struct _cpuid4_info_regs *base)
 {
+	this_leaf->id = base->id;
+	/* Set CACHE_ID bit in attributes to enable cache id in x86. */
+	this_leaf->attributes = CACHE_ID;
 	this_leaf->level = base->eax.split.level;
 	this_leaf->type = cache_type_map[base->eax.split.type];
 	this_leaf->coherency_line_size =
@@ -920,6 +924,22 @@ static int __init_cache_level(unsigned int cpu)
 	return 0;
 }
 
+/*
+ * The max shared threads number comes from CPUID.4:EAX[25-14] with input
+ * ECX as cache index. Then right shift apicid by the number's order to get
+ * cache id for this cache node.
+ */
+static void get_cache_id(int cpu, struct _cpuid4_info_regs *id4_regs)
+{
+	struct cpuinfo_x86 *c = &cpu_data(cpu);
+	unsigned long num_threads_sharing;
+	int index_msb;
+
+	num_threads_sharing = 1 + id4_regs->eax.split.num_threads_sharing;
+	index_msb = get_count_order(num_threads_sharing);
+	id4_regs->id = c->apicid >> index_msb;
+}
+
 static int __populate_cache_leaves(unsigned int cpu)
 {
 	unsigned int idx, ret;
@@ -931,6 +951,7 @@ static int __populate_cache_leaves(unsigned int cpu)
 		ret = cpuid4_cache_lookup_regs(idx, &id4_regs);
 		if (ret)
 			return ret;
+		get_cache_id(cpu, &id4_regs);
 		ci_leaf_init(this_leaf++, &id4_regs);
 		__cache_cpumap_setup(cpu, idx, &id4_regs);
 	}
diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index e9fd32e..2a21c15 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -233,6 +233,7 @@ static ssize_t file_name##_show(struct device *dev,		\
 	return sprintf(buf, "%u\n", this_leaf->object);		\
 }
 
+show_one(id, id);
 show_one(level, level);
 show_one(coherency_line_size, coherency_line_size);
 show_one(number_of_sets, number_of_sets);
@@ -314,6 +315,7 @@ static ssize_t write_policy_show(struct device *dev,
 	return n;
 }
 
+static DEVICE_ATTR_RO(id);
 static DEVICE_ATTR_RO(level);
 static DEVICE_ATTR_RO(type);
 static DEVICE_ATTR_RO(coherency_line_size);
@@ -327,6 +329,7 @@ static DEVICE_ATTR_RO(shared_cpu_list);
 static DEVICE_ATTR_RO(physical_line_partition);
 
 static struct attribute *cache_default_attrs[] = {
+	&dev_attr_id.attr,
 	&dev_attr_type.attr,
 	&dev_attr_level.attr,
 	&dev_attr_shared_cpu_map.attr,
@@ -350,6 +353,8 @@ cache_default_attrs_is_visible(struct kobject *kobj,
 	const struct cpumask *mask = &this_leaf->shared_cpu_map;
 	umode_t mode = attr->mode;
 
+	if ((attr == &dev_attr_id.attr) && this_leaf->attributes & CACHE_ID)
+		return mode;
 	if ((attr == &dev_attr_type.attr) && this_leaf->type)
 		return mode;
 	if ((attr == &dev_attr_level.attr) && this_leaf->level)
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index 2189935..16e5573 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -18,6 +18,7 @@ enum cache_type {
 
 /**
  * struct cacheinfo - represent a cache leaf node
+ * @id: id of this cache node. This is unique id across the platform.
  * @type: type of the cache - data, inst or unified
  * @level: represents the hierarchy in the multi-level cache
  * @coherency_line_size: size of each cache line usually representing
@@ -44,6 +45,7 @@ enum cache_type {
  * keeping, the remaining members form the core properties of the cache
  */
 struct cacheinfo {
+	unsigned int id;
 	enum cache_type type;
 	unsigned int level;
 	unsigned int coherency_line_size;
@@ -61,6 +63,7 @@ struct cacheinfo {
 #define CACHE_WRITE_ALLOCATE	BIT(3)
 #define CACHE_ALLOCATE_POLICY_MASK	\
 	(CACHE_READ_ALLOCATE | CACHE_WRITE_ALLOCATE)
+#define CACHE_ID		BIT(4)
 
 	struct device_node *of_node;
 	bool disable_sysfs;
-- 
2.5.0