[v3,09/19] x86/cpu: Clear VMX feature flag if VMX is not fully enabled

Commit Message

Sean Christopherson Nov. 19, 2019, 3:12 a.m. UTC

Now that the IA32_FEATURE_CONTROL MSR is guaranteed to be configured and
locked, clear the VMX capability flag if the IA32_FEATURE_CONTROL MSR is
not supported or if BIOS disabled VMX, i.e. locked IA32_FEATURE_CONTROL
and did not set the appropriate VMX enable bit.

Signed-off-by: Sean Christopherson <[e-mail]>
---
 arch/x86/kernel/cpu/feature_control.c | 28 ++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

Patch

diff --git a/arch/x86/kernel/cpu/feature_control.c b/arch/x86/kernel/cpu/feature_control.c
index 33c9444dda52..2bd1a9e6021a 100644
--- a/arch/x86/kernel/cpu/feature_control.c
+++ b/arch/x86/kernel/cpu/feature_control.c
@@ -5,15 +5,26 @@ 
 #include <asm/msr-index.h>
 #include <asm/processor.h>
 
+#undef pr_fmt
+#define pr_fmt(fmt)	"x86/cpu: " fmt
+
+#define FEAT_CTL_UNSUPPORTED_MSG "IA32_FEATURE_CONTROL MSR unsupported on VMX capable CPU, suspected hardware or hypervisor issue.\n"
+
 void init_feature_control_msr(struct cpuinfo_x86 *c)
 {
+	bool tboot = tboot_enabled();
 	u64 msr;
 
-	if (rdmsrl_safe(MSR_IA32_FEATURE_CONTROL, &msr))
+	if (rdmsrl_safe(MSR_IA32_FEATURE_CONTROL, &msr)) {
+		if (cpu_has(c, X86_FEATURE_VMX)) {
+			pr_err_once(FEAT_CTL_UNSUPPORTED_MSG);
+			clear_cpu_cap(c, X86_FEATURE_VMX);
+		}
 		return;
+	}
 
 	if (msr & FEAT_CTL_LOCKED)
-		return;
+		goto update_caps;
 
 	/*
 	 * Ignore whatever value BIOS left in the MSR to avoid enabling random
@@ -28,8 +39,19 @@  void init_feature_control_msr(struct cpuinfo_x86 *c)
 	 */
 	if (cpu_has(c, X86_FEATURE_VMX) && IS_ENABLED(CONFIG_KVM)) {
 		msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
-		if (tboot_enabled())
+		if (tboot)
 			msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
 	}
 	wrmsrl(MSR_IA32_FEATURE_CONTROL, msr);
+
+update_caps:
+	if (!cpu_has(c, X86_FEATURE_VMX))
+		return;
+
+	if ((tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
+	    (!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
+		pr_err_once("VMX (%s TXT) disabled by BIOS\n",
+			    tboot ? "inside" : "outside");
+		clear_cpu_cap(c, X86_FEATURE_VMX);
+	}
 }