x86/HVM: consistently check CR0.EM in hvmemul_get_fpu()

I'm pretty certain I had meant to make this a follow-up to what is now
11c35f84b5 ("x86/emulator: generalize movq emulation (SSE2 and AVX
variants)"), but I obviously never did. Correct this: Just like SSE
insns, FPU and MMX ones require CR0.EM to be clear.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Albeit perhaps we should really make this deliver #NM instead of
returning "unhandleable", but that's a separate step to take.

--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1628,9 +1628,12 @@ static int hvmemul_get_fpu(
     switch ( type )
     {
     case X86EMUL_FPU_fpu:
+        if ( (curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_EM) )
+            return X86EMUL_UNHANDLEABLE;
         break;
     case X86EMUL_FPU_mmx:
-        if ( !cpu_has_mmx )
+        if ( !cpu_has_mmx ||
+             (curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_EM) )
             return X86EMUL_UNHANDLEABLE;
         break;
     case X86EMUL_FPU_xmm: