5 files changed, 48 insertions, 0 deletions
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index af9c967782f6..98be76fa2978 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -387,6 +387,10 @@ config X86_DEBUGCTLMSR
 	def_bool y
 	depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486SX || M486) && !UML
 
+config IA32_FEAT_CTL
+	def_bool y
+	depends on CPU_SUP_INTEL
+
 menuconfig PROCESSOR_SELECT
 	bool "Supported processor vendors" if EXPERT
 	---help---
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 890f60083eca..57652c603929 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -29,6 +29,7 @@ obj-y			+= umwait.o
 obj-$(CONFIG_PROC_FS)	+= proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
 
+obj-$(CONFIG_IA32_FEAT_CTL) += feat_ctl.o
 ifdef CONFIG_CPU_SUP_INTEL
 obj-y			+= intel.o intel_pconfig.o tsx.o
 obj-$(CONFIG_PM)	+= intel_epb.o
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index 38ab6e115eac..37fdefd14f28 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -80,4 +80,8 @@ extern void x86_spec_ctrl_setup_ap(void);
 
 extern u64 x86_read_arch_cap_msr(void);
 
+#ifdef CONFIG_IA32_FEAT_CTL
+void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
+#endif
+
 #endif /* ARCH_X86_CPU_H */
diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
new file mode 100644
index 000000000000..c4f8f767853b
--- /dev/null
+++ b/arch/x86/kernel/cpu/feat_ctl.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/tboot.h>
+
+#include <asm/cpufeature.h>
+#include <asm/msr-index.h>
+#include <asm/processor.h>
+
+void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
+{
+	u64 msr;
+
+	if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr))
+		return;
+
+	if (msr & FEAT_CTL_LOCKED)
+		return;
+
+	/*
+	 * Ignore whatever value BIOS left in the MSR to avoid enabling random
+	 * features or faulting on the WRMSR.
+	 */
+	msr = FEAT_CTL_LOCKED;
+
+	/*
+	 * Enable VMX if and only if the kernel may do VMXON at some point,
+	 * i.e. KVM is enabled, to avoid unnecessarily adding an attack vector
+	 * for the kernel, e.g. using VMX to hide malicious code.
+	 */
+	if (cpu_has(c, X86_FEATURE_VMX) && IS_ENABLED(CONFIG_KVM_INTEL)) {
+		msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
+
+		if (tboot_enabled())
+			msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
+	}
+
+	wrmsrl(MSR_IA32_FEAT_CTL, msr);
+}
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 4a900804a023..9129c170ea11 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -755,6 +755,8 @@ static void init_intel(struct cpuinfo_x86 *c)
 	/* Work around errata */
 	srat_detect_node(c);
 
+	init_ia32_feat_ctl(c);
+
 	if (cpu_has(c, X86_FEATURE_VMX))
 		detect_vmx_virtcap(c);