KVM: VMX: Use VMX feature flag to query BIOS enabling

Replace KVM's manual checks on IA32_FEAT_CTL with a query on the boot
CPU's MSR_IA32_FEAT_CTL and VMX feature flags.  The MSR_IA32_FEAT_CTL
indicates that IA32_FEAT_CTL has been configured and that dependent
features are accurately reflected in cpufeatures, e.g. the VMX flag is
now cleared during boot if VMX isn't fully enabled via IA32_FEAT_CTL,
including the case where the MSR isn't supported.

Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: Sean Christopherson

arch/x86/kvm/vmx/vmx.c

@@ -2204,31 +2204,8 @@ static __init int cpu_has_kvm_support(void)
 
 static __init int vmx_disabled_by_bios(void)
 {
-	u64 msr;
-
-	rdmsrl(MSR_IA32_FEAT_CTL, msr);
-
-	if (unlikely(!(msr & FEAT_CTL_LOCKED)))
-		return 1;
-
-	/* launched w/ TXT and VMX disabled */
-	if (!(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX) &&
-	    tboot_enabled())
-		return 1;
-	/* launched w/o TXT and VMX only enabled w/ TXT */
-	if (!(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX) &&
-	    (msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX) &&
-	    !tboot_enabled()) {
-		pr_warn("kvm: disable TXT in the BIOS or "
-			"activate TXT before enabling KVM\n");
-		return 1;
-	}
-	/* launched w/o TXT and VMX disabled */
-	if (!(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX) &&
-	    !tboot_enabled())
-		return 1;
-
-	return 0;
+	return !boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
+	       !boot_cpu_has(X86_FEATURE_VMX);
 }
 
 static void kvm_cpu_vmxon(u64 addr)