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Subject[PATCH 01/01] x86: L3 cache index disable for 2.6.26
Date
New versions of AMD processors have support to disable parts
of their L3 caches if too many MCEs are generated by the
L3 cache.

This patch provides a /sysfs interface under the cache
hierarchy to display which caches indices are disabled
(if any) and to monitoring applications to disable a
cache index.

This patch does not set an automatic policy to disable
the L3 cache. Policy decisions would need to be made
by a RAS handler. This patch merely makes it easier to
see what indices are currently disabled.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>

---
-Mark Langsdorf
Operating System Research Center
AMD


diff -r 3836aaac6e15 arch/x86/kernel/cpu/intel_cacheinfo.c
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c Tue Jul 15 14:55:36 2008 -0500
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c Thu Jul 17 16:18:40 2008 -0500
@@ -16,6 +16,7 @@

#include <asm/processor.h>
#include <asm/smp.h>
+#include <asm/k8.h>

#define LVL_1_INST 1
#define LVL_1_DATA 2
@@ -129,6 +130,7 @@ struct _cpuid4_info {
union _cpuid4_leaf_ebx ebx;
union _cpuid4_leaf_ecx ecx;
unsigned long size;
+ unsigned long can_disable;
cpumask_t shared_cpu_map; /* future?: only cpus/node is needed */
};

@@ -250,6 +252,13 @@ static void __cpuinit amd_cpuid4(int lea
(ebx->split.ways_of_associativity + 1) - 1;
}

+static void __cpuinit amd_check_l3_disable(int index, struct _cpuid4_info *this_leaf)
+{
+ if (index < 3)
+ return;
+ this_leaf->can_disable = 1;
+}
+
static int __cpuinit cpuid4_cache_lookup(int index, struct _cpuid4_info *this_leaf)
{
union _cpuid4_leaf_eax eax;
@@ -257,9 +266,12 @@ static int __cpuinit cpuid4_cache_lookup
union _cpuid4_leaf_ecx ecx;
unsigned edx;

- if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
amd_cpuid4(index, &eax, &ebx, &ecx);
- else
+ if (boot_cpu_data.x86 >= 0x10)
+ amd_check_l3_disable(index, this_leaf);
+
+ } else
cpuid_count(4, index, &eax.full, &ebx.full, &ecx.full, &edx);
if (eax.split.type == CACHE_TYPE_NULL)
return -EIO; /* better error ? */
@@ -636,6 +648,61 @@ static ssize_t show_type(struct _cpuid4_
}
}

+#define to_object(k) container_of(k, struct _index_kobject, kobj)
+#define to_attr(a) container_of(a, struct _cache_attr, attr)
+
+static ssize_t show_cache_disable(struct _cpuid4_info *this_leaf, char *buf)
+{
+ struct pci_dev *dev;
+ if (this_leaf->can_disable) {
+ int i;
+ ssize_t ret = 0;
+ int node = cpu_to_node(first_cpu(this_leaf->shared_cpu_map));
+ dev = k8_northbridges[node];
+
+ for (i = 0; i < 2; i++) {
+ unsigned int reg;
+ pci_read_config_dword(dev, 0x1BC + i * 4, &reg);
+ ret += sprintf(buf, "%sEntry: %d\n", buf, i);
+ ret += sprintf(buf, "%sReads: %s\tNew Entries: %s\n",
+ buf,
+ reg & 0x80000000 ? "Disabled" : "Allowed",
+ reg & 0x40000000 ? "Disabled" : "Allowed");
+ ret += sprintf(buf, "%sSubCache: %x\tIndex: %x\n", buf,
+ (reg & 0x30000) >> 16, reg & 0xfff);
+
+ }
+ return ret;
+ }
+ return sprintf(buf, "Feature not enabled\n");
+}
+
+static ssize_t store_cache_disable(struct _cpuid4_info *this_leaf, const char *buf, size_t count)
+{
+ struct pci_dev *dev;
+ if (this_leaf->can_disable) {
+ /* write the MSR value */
+ unsigned int ret;
+ unsigned int index, val;
+ int node = cpu_to_node(first_cpu(this_leaf->shared_cpu_map));
+ dev = k8_northbridges[node];
+
+ if (strlen(buf) > 15)
+ return -EINVAL;
+ ret = sscanf(buf, "%x %x", &index, &val);
+ if (ret != 2)
+ return -EINVAL;
+ if (index > 1)
+ return -EINVAL;
+ val |= 0xc0000000;
+ pci_write_config_dword(dev, 0x1BC + index * 4, val & ~0x40000000);
+ wbinvd();
+ pci_write_config_dword(dev, 0x1BC + index * 4, val);
+ return 1;
+ }
+ return 0;
+}
+
struct _cache_attr {
struct attribute attr;
ssize_t (*show)(struct _cpuid4_info *, char *);
@@ -655,6 +722,8 @@ define_one_ro(size);
define_one_ro(size);
define_one_ro(shared_cpu_map);
define_one_ro(shared_cpu_list);
+
+static struct _cache_attr cache_disable = __ATTR(cache_disable, 0644, show_cache_disable, store_cache_disable);

static struct attribute * default_attrs[] = {
&type.attr,
@@ -666,11 +735,9 @@ static struct attribute * default_attrs[
&size.attr,
&shared_cpu_map.attr,
&shared_cpu_list.attr,
+ &cache_disable.attr,
NULL
};
-
-#define to_object(k) container_of(k, struct _index_kobject, kobj)
-#define to_attr(a) container_of(a, struct _cache_attr, attr)

static ssize_t show(struct kobject * kobj, struct attribute * attr, char * buf)
{
@@ -688,7 +755,15 @@ static ssize_t store(struct kobject * ko
static ssize_t store(struct kobject * kobj, struct attribute * attr,
const char * buf, size_t count)
{
- return 0;
+ struct _cache_attr *fattr = to_attr(attr);
+ struct _index_kobject *this_leaf = to_object(kobj);
+ ssize_t ret;
+
+ ret = fattr->store ?
+ fattr->store(CPUID4_INFO_IDX(this_leaf->cpu, this_leaf->index),
+ buf, count) :
+ 0;
+ return ret;
}

static struct sysfs_ops sysfs_ops = {
-------------------------------------------------------


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