linux-kernel - [PATCH v2 06/16] x86/cpu: Clear VMX feature flag if VMX is not fully enabled

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Date:   Mon, 21 Oct 2019 17:08:36 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH v2 06/16] x86/cpu: Clear VMX feature flag if VMX is not fully enabled

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.

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: Wanpeng Li <wanpengli@...cent.com>
Cc: Jim Mattson <jmattson@...gle.com>
Cc: kvm@...r.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kernel/cpu/feature_control.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/feature_control.c b/arch/x86/kernel/cpu/feature_control.c
index 57b928e64cf5..74c76159a046 100644
--- a/arch/x86/kernel/cpu/feature_control.c
+++ b/arch/x86/kernel/cpu/feature_control.c
@@ -7,13 +7,19 @@
 
 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("x86/cpu: VMX disabled, IA32_FEATURE_CONTROL MSR unsupported\n");
+			clear_cpu_cap(c, X86_FEATURE_VMX);
+		}
 		return;
+	}
 
 	if (msr & FEATURE_CONTROL_LOCKED)
-		return;
+		goto update_caps;
 
 	/*
 	 * Ignore whatever value BIOS left in the MSR to avoid enabling random
@@ -23,8 +29,19 @@ void init_feature_control_msr(struct cpuinfo_x86 *c)
 
 	if (cpu_has(c, X86_FEATURE_VMX)) {
 		msr |= FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
-		if (tboot_enabled())
+		if (tboot)
 			msr |= FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX;
 	}
 	wrmsrl(MSR_IA32_FEATURE_CONTROL, msr);
+
+update_caps:
+	if (!cpu_has(c, X86_FEATURE_VMX))
+		return;
+
+	if ((tboot && !(msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX)) ||
+	    (!tboot && !(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX))) {
+		pr_err_once("x86/cpu: VMX disabled by BIOS (TXT %s)\n",
+			    tboot ? "enabled" : "disabled");
+		clear_cpu_cap(c, X86_FEATURE_VMX);
+	}
 }
-- 
2.22.0