1 files changed, 47 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/tsx.c b/arch/x86/kernel/cpu/tsx.c
index ec6ff8000920..ec7bbac3a9f2 100644
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -19,7 +19,7 @@
 
 enum tsx_ctrl_states tsx_ctrl_state __ro_after_init = TSX_CTRL_NOT_SUPPORTED;
 
-void tsx_disable(void)
+static void tsx_disable(void)
 {
 	u64 tsx;
 
@@ -39,7 +39,7 @@ void tsx_disable(void)
 	wrmsrl(MSR_IA32_TSX_CTRL, tsx);
 }
 
-void tsx_enable(void)
+static void tsx_enable(void)
 {
 	u64 tsx;
 
@@ -122,7 +122,7 @@ static enum tsx_ctrl_states x86_get_tsx_auto_mode(void)
  * That's why, this function's call in init_intel() doesn't clear the
  * feature flags.
  */
-void tsx_clear_cpuid(void)
+static void tsx_clear_cpuid(void)
 {
 	u64 msr;
 
@@ -142,11 +142,42 @@ void tsx_clear_cpuid(void)
 	}
 }
 
+/*
+ * Disable TSX development mode
+ *
+ * When the microcode released in Feb 2022 is applied, TSX will be disabled by
+ * default on some processors. MSR 0x122 (TSX_CTRL) and MSR 0x123
+ * (IA32_MCU_OPT_CTRL) can be used to re-enable TSX for development, doing so is
+ * not recommended for production deployments. In particular, applying MD_CLEAR
+ * flows for mitigation of the Intel TSX Asynchronous Abort (TAA) transient
+ * execution attack may not be effective on these processors when Intel TSX is
+ * enabled with updated microcode.
+ */
+static void tsx_dev_mode_disable(void)
+{
+	u64 mcu_opt_ctrl;
+
+	/* Check if RTM_ALLOW exists */
+	if (!boot_cpu_has_bug(X86_BUG_TAA) || !tsx_ctrl_is_supported() ||
+	    !cpu_feature_enabled(X86_FEATURE_SRBDS_CTRL))
+		return;
+
+	rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_opt_ctrl);
+
+	if (mcu_opt_ctrl & RTM_ALLOW) {
+		mcu_opt_ctrl &= ~RTM_ALLOW;
+		wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_opt_ctrl);
+		setup_force_cpu_cap(X86_FEATURE_RTM_ALWAYS_ABORT);
+	}
+}
+
 void __init tsx_init(void)
 {
 	char arg[5] = {};
 	int ret;
 
+	tsx_dev_mode_disable();
+
 	/*
 	 * Hardware will always abort a TSX transaction when the CPUID bit
 	 * RTM_ALWAYS_ABORT is set. In this case, it is better not to enumerate
@@ -215,3 +246,16 @@ void __init tsx_init(void)
 		setup_force_cpu_cap(X86_FEATURE_HLE);
 	}
 }
+
+void tsx_ap_init(void)
+{
+	tsx_dev_mode_disable();
+
+	if (tsx_ctrl_state == TSX_CTRL_ENABLE)
+		tsx_enable();
+	else if (tsx_ctrl_state == TSX_CTRL_DISABLE)
+		tsx_disable();
+	else if (tsx_ctrl_state == TSX_CTRL_RTM_ALWAYS_ABORT)
+		/* See comment over that function for more details. */
+		tsx_clear_cpuid();
+}