[PATCH 4/9] x86/intel_rdt: Add support for Cache Allocation detection

From: Vikas Shivappa
Date: Thu Jun 25 2015 - 15:29:52 EST

This patch adds support for Cache Allocation Technology feature found in
future Intel Xeon processors. Cache allocation is a sub-feature of Intel
Resource Director Technology(RDT) which enables sharing of processor
resources. This patch includes CPUID enumeration routines for Cache
allocation and new values to track resources to the cpuinfo_x86
structure.

Cache allocation provides a way for the Software (OS/VMM) to restrict
cache allocation to a defined 'subset' of cache which may be overlapping
with other 'subsets'. This feature is used when allocating a line in
cache ie when pulling new data into the cache. The programming of the
hardware is done via programming MSRs(model specific registers).

More information about Cache allocation be found in the Intel (R) x86
Architecture Software Developer Manual,Volume 3, section 17.15.

Signed-off-by: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/cpufeature.h | 6 +++++-
arch/x86/include/asm/processor.h | 3 +++
arch/x86/kernel/cpu/Makefile | 1 +
arch/x86/kernel/cpu/common.c | 15 +++++++++++++++
arch/x86/kernel/cpu/intel_rdt.c | 40 +++++++++++++++++++++++++++++++++++++++
init/Kconfig | 11 +++++++++++
6 files changed, 75 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/kernel/cpu/intel_rdt.c

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 3d6606f..ae5ae9d 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -12,7 +12,7 @@
#include <asm/disabled-features.h>
#endif

-#define NCAPINTS 13 /* N 32-bit words worth of info */
+#define NCAPINTS 14 /* N 32-bit words worth of info */
#define NBUGINTS 1 /* N 32-bit bug flags */

/*
@@ -229,6 +229,7 @@
#define X86_FEATURE_RTM ( 9*32+11) /* Restricted Transactional Memory */
#define X86_FEATURE_CQM ( 9*32+12) /* Cache QoS Monitoring */
#define X86_FEATURE_MPX ( 9*32+14) /* Memory Protection Extension */
+#define X86_FEATURE_RDT ( 9*32+15) /* Resource Allocation */
#define X86_FEATURE_AVX512F ( 9*32+16) /* AVX-512 Foundation */
#define X86_FEATURE_RDSEED ( 9*32+18) /* The RDSEED instruction */
#define X86_FEATURE_ADX ( 9*32+19) /* The ADCX and ADOX instructions */
@@ -252,6 +253,9 @@
/* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
#define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */

+/* Intel-defined CPU features, CPUID level 0x00000010:0 (ebx), word 13 */
+#define X86_FEATURE_CAT_L3 (13*32 + 1) /* Cache Allocation L3 */
+
/*
* BUG word(s)
*/
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 23ba676..16ca766 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -114,6 +114,9 @@ struct cpuinfo_x86 {
int x86_cache_occ_scale; /* scale to bytes */
int x86_power;
unsigned long loops_per_jiffy;
+ /* Cache Allocation values: */
+ u16 x86_cache_max_cbm_len;
+ u16 x86_cache_max_closid;
/* cpuid returned max cores value: */
u16 x86_max_cores;
u16 apicid;
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 9bff687..4ff7a1f 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_PERF_EVENTS_INTEL_UNCORE) += perf_event_intel_uncore.o \
perf_event_intel_uncore_nhmex.o
endif

+obj-$(CONFIG_CGROUP_RDT) += intel_rdt.o

obj-$(CONFIG_X86_MCE) += mcheck/
obj-$(CONFIG_MTRR) += mtrr/
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a62cf04..fd014f5 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -670,6 +670,21 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
}
}

+ /* Additional Intel-defined flags: level 0x00000010 */
+ if (c->cpuid_level >= 0x00000010) {
+ u32 eax, ebx, ecx, edx;
+
+ cpuid_count(0x00000010, 0, &eax, &ebx, &ecx, &edx);
+ c->x86_capability[13] = ebx;
+
+ if (cpu_has(c, X86_FEATURE_CAT_L3)) {
+
+ cpuid_count(0x00000010, 1, &eax, &ebx, &ecx, &edx);
+ c->x86_cache_max_closid = edx + 1;
+ c->x86_cache_max_cbm_len = eax + 1;
+ }
+ }
+
/* AMD-defined flags: level 0x80000001 */
xlvl = cpuid_eax(0x80000000);
c->extended_cpuid_level = xlvl;
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
new file mode 100644
index 0000000..3cd6db6
--- /dev/null
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -0,0 +1,40 @@
+/*
+ * Resource Director Technology(RDT)
+ * - Cache Allocation code.
+ *
+ * Copyright (C) 2014 Intel Corporation
+ *
+ * 2015-05-25 Written by
+ * Vikas Shivappa <vikas.shivappa@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * More information about RDT be found in the Intel (R) x86 Architecture
+ * Software Developer Manual, volume 3, section 17.15.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/err.h>
+
+static int __init intel_rdt_late_init(void)
+{
+ struct cpuinfo_x86 *c = &boot_cpu_data;
+
+ if (!cpu_has(c, X86_FEATURE_CAT_L3))
+ return -ENODEV;
+
+ pr_info("Intel cache allocation enabled\n");
+
+ return 0;
+}
+
+late_initcall(intel_rdt_late_init);
diff --git a/init/Kconfig b/init/Kconfig
index 81050e4..203f116 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -983,6 +983,17 @@ config CPUSETS

Say N if unsure.

+config CGROUP_RDT
+ bool "Resource Director Technology cgroup subsystem"
+ depends on X86_64 && CPU_SUP_INTEL
+ help
+ This option provides a cgroup to allocate Platform shared
+ resources. Among the shared resources, current implementation
+ focuses on L3 Cache. Using the interface user can specify the
+ amount of L3 cache space into which an application can fill.
+
+ Say N if unsure.
+
config PROC_PID_CPUSET
bool "Include legacy /proc/<pid>/cpuset file"
depends on CPUSETS
--
1.9.1

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