KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

This msr is only available when the host supports WAITPKG feature.

This breaks a nested guest, if the L1 hypervisor is set to ignore
unknown msrs, because the only other safety check that the
kernel does is that it attempts to read the msr and
rejects it if it gets an exception.

Cc: [email protected]
Fixes: 6e3ba4a ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
Signed-off-by: Maxim Levitsky <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: Maxim Levitsky

arch/x86/kvm/x86.c

@@ -5242,6 +5242,10 @@ static void kvm_init_msr_list(void)
 			if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
 				continue;
 			break;
+		case MSR_IA32_UMWAIT_CONTROL:
+			if (!kvm_cpu_cap_has(X86_FEATURE_WAITPKG))
+				continue;
+			break;
 		case MSR_IA32_RTIT_CTL:
 		case MSR_IA32_RTIT_STATUS:
 			if (!kvm_cpu_cap_has(X86_FEATURE_INTEL_PT))