kvm: x86: Add kvm_x86_ops hook that enables XSAVES for guest

Expose the XSAVES feature to the guest if the kvm_x86_ops say it is
available.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

@@ -4127,6 +4127,11 @@ static bool svm_mpx_supported(void)
 	return false;
 }
 
+static bool svm_xsaves_supported(void)
+{
+	return false;
+}
+
 static bool svm_has_wbinvd_exit(void)
 {
 	return true;
@@ -4414,6 +4419,7 @@ static struct kvm_x86_ops svm_x86_ops = {
 	.rdtscp_supported = svm_rdtscp_supported,
 	.invpcid_supported = svm_invpcid_supported,
 	.mpx_supported = svm_mpx_supported,
+	.xsaves_supported = svm_xsaves_supported,
 
 	.set_supported_cpuid = svm_set_supported_cpuid,