[PATCH v10 3/6] x86/split_lock: Enumerate split lock detection by the IA32_CORE_CAPABILITIES MSR

[Fenghua Yu]

Bits in the IA32_CORE_CAPABILITIES MSR enumerate a few features that are
not enumerated through CPUID. Currently bit 5 is defined to enumerate
the feature of split lock detection. All other bits are reserved now.

When bit 5 is 1, the feature is supported and feature bit
X86_FEATURE_SPLIT_LOCK_DETECT is set. Otherwise, the feature is not
available.

The flag shown in /proc/cpuinfo is "split_lock_detect".

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/include/asm/cpu.h         |  5 +++++
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/kernel/cpu/common.c       |  2 ++
 arch/x86/kernel/cpu/intel.c        | 19 +++++++++++++++++++
 4 files changed, 27 insertions(+)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index adc6cc86b062..4e03f53fc079 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -40,4 +40,9 @@ int mwait_usable(const struct cpuinfo_x86 *);
 unsigned int x86_family(unsigned int sig);
 unsigned int x86_model(unsigned int sig);
 unsigned int x86_stepping(unsigned int sig);
+#ifdef CONFIG_CPU_SUP_INTEL
+void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c);
+#else
+static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {}
+#endif
 #endif /* _ASM_X86_CPU_H */
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index d708a1f83f40..92be003c02ba 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -220,6 +220,7 @@
 #define X86_FEATURE_ZEN			( 7*32+28) /* "" CPU is AMD family 0x17 (Zen) */
 #define X86_FEATURE_L1TF_PTEINV		( 7*32+29) /* "" L1TF workaround PTE inversion */
 #define X86_FEATURE_IBRS_ENHANCED	( 7*32+30) /* Enhanced IBRS */
+#define X86_FEATURE_SPLIT_LOCK_DETECT	( 7*32+31) /* #AC for split lock */
 
 /* Virtualization flags: Linux defined, word 8 */
 #define X86_FEATURE_TPR_SHADOW		( 8*32+ 0) /* Intel TPR Shadow */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index fffe21945374..2ee5fd49266f 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1235,6 +1235,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
 	cpu_set_bug_bits(c);
 
+	cpu_set_core_cap_bits(c);
+
 	fpu__init_system(c);
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 11d5c5950e2d..ce87e2c68767 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -1028,3 +1028,22 @@ static const struct cpu_dev intel_cpu_dev = {
 };
 
 cpu_dev_register(intel_cpu_dev);
+
+static void __init split_lock_setup(void)
+{
+	setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT);
+}
+
+void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c)
+{
+	u64 ia32_core_caps = 0;
+
+	if (!cpu_has(c, X86_FEATURE_CORE_CAPABILITIES))
+		return;
+
+	/* Enumerate features reported in IA32_CORE_CAPABILITIES MSR. */
+	rdmsrl(MSR_IA32_CORE_CAPABILITIES, ia32_core_caps);
+
+	if (ia32_core_caps & MSR_IA32_CORE_CAPABILITIES_SPLIT_LOCK_DETECT)
+		split_lock_setup();
+}
-- 
2.19.1