[PATCH v8 13/15] x86/split_lock: Enable split lock detection by default

[Fenghua Yu]

A split locked access locks bus and degrades overall memory access
performance. When split lock detection feature is enumerated, enable
the feature by default by writing 1 to bit 29 in MSR TEST_CTL to find
any split lock issue.

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
 arch/x86/kernel/cpu/intel.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 2cc69217ca7c..28cc6891ba48 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -657,6 +657,13 @@ static void init_intel_misc_features(struct cpuinfo_x86 *c)
 	wrmsrl(MSR_MISC_FEATURES_ENABLES, msr);
 }
 
+static void split_lock_update_msr(void)
+{
+	/* Enable split lock detection */
+	msr_set_bit(MSR_TEST_CTL, TEST_CTL_SPLIT_LOCK_DETECT_SHIFT);
+	this_cpu_or(msr_test_ctl_cache, TEST_CTL_SPLIT_LOCK_DETECT);
+}
+
 static void init_split_lock_detect(struct cpuinfo_x86 *c)
 {
 	if (cpu_has(c, X86_FEATURE_SPLIT_LOCK_DETECT)) {
@@ -665,6 +672,8 @@ static void init_split_lock_detect(struct cpuinfo_x86 *c)
 		/* Cache MSR TEST_CTL */
 		rdmsrl(MSR_TEST_CTL, test_ctl_val);
 		this_cpu_write(msr_test_ctl_cache, test_ctl_val);
+
+		split_lock_update_msr();
 	}
 }
 
@@ -1045,9 +1054,13 @@ static const struct cpu_dev intel_cpu_dev = {
 
 cpu_dev_register(intel_cpu_dev);
 
+#undef pr_fmt
+#define pr_fmt(fmt) "x86/split lock detection: " fmt
+
 static void __init set_split_lock_detect(void)
 {
 	setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT);
+	pr_info("enabled\n");
 }
 
 void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c)
-- 
2.19.1