x86/VMX: don't needlessly install VMFUNC emulation hook

Instead of checking cpu_has_vmx_vmfunc inside the hook, use it to
determine whether to install the hook in the first place.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2011,7 +2011,7 @@ static int vmx_vcpu_emulate_vmfunc(const
     int rc = X86EMUL_EXCEPTION;
     struct vcpu *curr = current;
 
-    if ( !cpu_has_vmx_vmfunc && altp2m_active(curr->domain) &&
+    if ( altp2m_active(curr->domain) &&
          regs->_eax == 0 &&
          p2m_switch_vcpu_altp2m_by_id(curr, regs->_ecx) )
         rc = X86EMUL_OKAY;
@@ -2155,7 +2155,6 @@ static struct hvm_function_table __initd
     .altp2m_vcpu_update_p2m = vmx_vcpu_update_eptp,
     .altp2m_vcpu_update_vmfunc_ve = vmx_vcpu_update_vmfunc_ve,
     .altp2m_vcpu_emulate_ve = vmx_vcpu_emulate_ve,
-    .altp2m_vcpu_emulate_vmfunc = vmx_vcpu_emulate_vmfunc,
     .tsc_scaling = {
         .max_ratio = VMX_TSC_MULTIPLIER_MAX,
         .setup     = vmx_setup_tsc_scaling,
@@ -2308,6 +2307,9 @@ const struct hvm_function_table * __init
         vmx_function_table.get_guest_bndcfgs = vmx_get_guest_bndcfgs;
     }
 
+    if ( !cpu_has_vmx_vmfunc )
+        vmx_function_table.altp2m_vcpu_emulate_vmfunc = vmx_vcpu_emulate_vmfunc;
+
     setup_vmcs_dump();
 
     return &vmx_function_table;