[PATCH 1/7] x86/intel_rdt: Intel Cache Allocation Technology detection

From: Vikas Shivappa
Date: Tue Mar 03 2015 - 18:36:49 EST

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

Cache Allocation Technology(CAT) 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 h/w is done via programming MSRs.

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

Signed-off-by: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>
---

Thanks for the feedback from Boris,Ingo,PeterZ,Tejun.Following changes made
based on comments:
-Improved the description of RDT specifying the cache level. Intel SDM chapter
number describing the technology is included in the code comment.
-Included 'depends CPU_SUP_INTEL' for RDT_config in init/Kconfig. Although
cpuid enumeration would check for the feature , its best to not have the code
active.
-Corrected space indent in the comment in cpufeature.h.
-Changed the CAT datastructure to u16 in cpuinfo.

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 | 51 +++++++++++++++++++++++++++++++++++++++
init/Kconfig | 11 +++++++++
6 files changed, 86 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 54fd8eb..eeef86c 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 */

/*
@@ -227,6 +227,7 @@
#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 */
@@ -248,6 +249,9 @@
/* 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 QOS Enforcement L3 */
+
/*
* BUG word(s)
*/
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 242ceed..80ac7e4 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 Technology values */
+ u16 x86_cat_cbmlength;
+ u16 x86_cat_closs;
/* 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 6c1ca13..eda32ff 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -47,6 +47,7 @@ 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 9b0fb70..c5ea1dd 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -668,6 +668,21 @@ 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_cat_closs = (edx & 0xffff) + 1;
+ c->x86_cat_cbmlength = (eax & 0xf) + 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..46ce449
--- /dev/null
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -0,0 +1,51 @@
+/*
+ * Resource Director Technology(RDT) code
+ *
+ * Copyright (C) 2014 Intel Corporation
+ *
+ * 2014-09-10 Written by Vikas Shivappa
+ *
+ * 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, section 17.15.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+
+static inline bool rdt_supported(struct cpuinfo_x86 *c)
+{
+ if (cpu_has(c, X86_FEATURE_RDT))
+ return true;
+
+ return false;
+}
+
+static int __init rdt_late_init(void)
+{
+ struct cpuinfo_x86 *c = &boot_cpu_data;
+ int maxid, cbm_len;
+
+ if (!rdt_supported(c))
+ return -ENODEV;
+
+ maxid = c->x86_cat_closs;
+ cbm_len = c->x86_cat_cbmlength;
+
+ pr_info("cbmlength:%u,Closs: %u\n", cbm_len, maxid);
+
+ return 0;
+}
+
+late_initcall(rdt_late_init);
diff --git a/init/Kconfig b/init/Kconfig
index 9afb971..3060a90 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -961,6 +961,17 @@ 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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