1 files changed, 37 insertions, 0 deletions
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);
+}