x86emul: minor cleanup

Drop a redundant input constraint, correct a comment, and (re)move
fix.insn_bytes adjustments (these aren't needed for custom stub
invocations when the instruction placed in the stub can't raise #XF)
plus a corresponding check_xmm_exn() invocation.

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

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -5681,8 +5681,7 @@ x86_emulate(
                     [eflags] "+g" (_regs.eflags),
                     [tmp] "=&r" (dummy), "+m" (*mmvalp),
                     "+m" (fic.exn_raised)
-                    : [func] "rm" (stub.func), "a" (mmvalp),
-                      [mask] "i" (EFLAGS_MASK));
+                    : "a" (mmvalp), [mask] "i" (EFLAGS_MASK));
 
         put_stub(stub);
         check_xmm_exn(&fic);
@@ -6086,7 +6085,7 @@ x86_emulate(
     case X86EMUL_OPC_F3(0x0f, 0x6f):     /* movdqu xmm/m128,xmm */
     case X86EMUL_OPC_VEX_F3(0x0f, 0x6f): /* vmovdqu {x,y}mm/mem,{x,y}mm */
     case X86EMUL_OPC_66(0x0f, 0x7f):     /* movdqa xmm,xmm/m128 */
-    case X86EMUL_OPC_VEX_66(0x0f, 0x7f): /* vmovdqa {x,y}mm,{x,y}mm/m128 */
+    case X86EMUL_OPC_VEX_66(0x0f, 0x7f): /* vmovdqa {x,y}mm,{x,y}mm/mem */
     case X86EMUL_OPC_F3(0x0f, 0x7f):     /* movdqu xmm,xmm/m128 */
     case X86EMUL_OPC_VEX_F3(0x0f, 0x7f): /* vmovdqu {x,y}mm,{x,y}mm/mem */
     movdqa:
@@ -7022,7 +7021,6 @@ x86_emulate(
         if ( !mode_64bit() )
             vex.w = 0;
         opc[1] = modrm & 0xc7;
-        fic.insn_bytes = PFX_BYTES + 2;
         opc[2] = 0xc3;
 
         copy_REX_VEX(opc, rex_prefix, vex);
@@ -7035,6 +7033,7 @@ x86_emulate(
         opc = init_prefixes(stub);
         opc[0] = b;
         opc[1] = modrm;
+        fic.insn_bytes = PFX_BYTES + 2;
         /* Restore high bit of XMM destination. */
         if ( sfence )
         {
@@ -7469,20 +7468,16 @@ x86_emulate(
             vex.w = 0;
         opc[1] = modrm & 0x38;
         opc[2] = imm1;
-        fic.insn_bytes = PFX_BYTES + 3;
         opc[3] = 0xc3;
         if ( vex.opcx == vex_none )
         {
             /* Cover for extra prefix byte. */
             --opc;
-            ++fic.insn_bytes;
         }
 
         copy_REX_VEX(opc, rex_prefix, vex);
         invoke_stub("", "", "=m" (dst.val) : "a" (&dst.val));
-
         put_stub(stub);
-        check_xmm_exn(&fic);
 
         ASSERT(!state->simd_size);
         dst.bytes = dst.type == OP_REG || b == 0x17 ? 4 : 1 << (b & 3);