[PATCH v4 07/17] x86/split_lock: Enumerate #AC for split lock by MSR IA32_CORE_CAPABILITY

[Fenghua Yu]

Bits in MSR IA32_CORE_CAPABILITY enumerate features that are not
enumerated through CPUID. Currently bit 5 is defined to enumerate
feature of #AC for split lock accesses. All other bits are reserved now.

When the 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 MSR IA32_CORE_CAPABILITY itself is enumerated by
CPUID.(EAX=0x7,ECX=0):EDX[30].

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
 arch/x86/include/asm/cpu.h         |  5 +++++
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/kernel/cpu/common.c       |  1 +
 arch/x86/kernel/cpu/cpuid-deps.c   |  1 +
 arch/x86/kernel/cpu/intel.c        | 21 +++++++++++++++++++++
 5 files changed, 29 insertions(+)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index adc6cc86b062..e241abce1a2a 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_core_capability(struct cpuinfo_x86 *c);
+#else
+static inline void init_core_capability(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 350eeccd0ce9..54c73e74213d 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -221,6 +221,7 @@
 #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 51ab37ba5f64..79e7cc0c4c85 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -897,6 +897,7 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 
 	init_scattered_cpuid_features(c);
 	init_speculation_control(c);
+	init_core_capability(c);
 
 	/*
 	 * Clear/Set all flags overridden by options, after probe.
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index 2c0bd38a44ab..5ba11ce99f92 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -59,6 +59,7 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_AVX512_4VNNIW,	X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512_4FMAPS,	X86_FEATURE_AVX512F   },
 	{ X86_FEATURE_AVX512_VPOPCNTDQ, X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_SPLIT_LOCK_DETECT, X86_FEATURE_CORE_CAPABILITY},
 	{}
 };
 
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index fc3c07fe7df5..0c44c49f6005 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -1029,3 +1029,24 @@ static const struct cpu_dev intel_cpu_dev = {
 
 cpu_dev_register(intel_cpu_dev);
 
+/**
+ * init_core_capability - enumerate features supported in IA32_CORE_CAPABILITY
+ * @c: pointer to cpuinfo_x86
+ *
+ * Return: void
+ */
+void init_core_capability(struct cpuinfo_x86 *c)
+{
+	/*
+	 * If MSR_IA32_CORE_CAPABILITY exists, enumerate features that are
+	 * reported in the MSR.
+	 */
+	if (c == &boot_cpu_data && cpu_has(c, X86_FEATURE_CORE_CAPABILITY)) {
+		u64 val;
+
+		rdmsrl(MSR_IA32_CORE_CAPABILITY, val);
+
+		if (val & CORE_CAP_SPLIT_LOCK_DETECT)
+			setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT);
+	}
+}
-- 
2.7.4