kvm: vmx: Raise #UD on unsupported XSAVES/XRSTORS

A guest may not be configured to support XSAVES/XRSTORS, even when the host
does. If the guest does not support XSAVES/XRSTORS, clear the secondary
execution control so that the processor will raise #UD.

Also clear the "allowed-1" bit for XSAVES/XRSTORS exiting in the
IA32_VMX_PROCBASED_CTLS2 MSR, and pass through VMCS12's control in
the VMCS02.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -1358,8 +1358,7 @@ static inline int nested_cpu_has_ept(struct vmcs12 *vmcs12)
 
 static inline bool nested_cpu_has_xsaves(struct vmcs12 *vmcs12)
 {
-	return nested_cpu_has2(vmcs12, SECONDARY_EXEC_XSAVES) &&
-		vmx_xsaves_supported();
+	return nested_cpu_has2(vmcs12, SECONDARY_EXEC_XSAVES);
 }
 
 static inline bool nested_cpu_has_pml(struct vmcs12 *vmcs12)
@@ -2823,8 +2822,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 		SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
 		SECONDARY_EXEC_APIC_REGISTER_VIRT |
 		SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
-		SECONDARY_EXEC_WBINVD_EXITING |
-		SECONDARY_EXEC_XSAVES;
+		SECONDARY_EXEC_WBINVD_EXITING;
 
 	if (enable_ept) {
 		/* nested EPT: emulate EPT also to L1 */
@@ -5319,6 +5317,25 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
 	if (!enable_pml)
 		exec_control &= ~SECONDARY_EXEC_ENABLE_PML;
 
+	if (vmx_xsaves_supported()) {
+		/* Exposing XSAVES only when XSAVE is exposed */
+		bool xsaves_enabled =
+			guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
+			guest_cpuid_has(vcpu, X86_FEATURE_XSAVES);
+
+		if (!xsaves_enabled)
+			exec_control &= ~SECONDARY_EXEC_XSAVES;
+
+		if (nested) {
+			if (xsaves_enabled)
+				vmx->nested.nested_vmx_secondary_ctls_high |=
+					SECONDARY_EXEC_XSAVES;
+			else
+				vmx->nested.nested_vmx_secondary_ctls_high &=
+					~SECONDARY_EXEC_XSAVES;
+		}
+	}
+
 	if (vmx_rdtscp_supported()) {
 		bool rdtscp_enabled = guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP);
 		if (!rdtscp_enabled)
@@ -10421,6 +10438,7 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		exec_control &= ~(SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
 				  SECONDARY_EXEC_ENABLE_INVPCID |
 				  SECONDARY_EXEC_RDTSCP |
+				  SECONDARY_EXEC_XSAVES |
 				  SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
 				  SECONDARY_EXEC_APIC_REGISTER_VIRT |
 				  SECONDARY_EXEC_ENABLE_VMFUNC);