x86/emul: Unfold %cr4.de handling in x86emul_read_dr()

No functional change (as curr->arch.debugreg[5] is zero when DE is clear), but
this change simplifies the following patch.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

diff --git a/xen/arch/x86/x86_emulate.c b/xen/arch/x86/x86_emulate.c
index 532b7e04e11e67a439b67a06f027ca0a499dccbf..e1153f76b252a1cfabdeef11a373c3f16045a938 100644 (file)
--- a/xen/arch/x86/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate.c
@@ -101,23 +101,29 @@ int x86emul_read_dr(unsigned int reg, unsigned long *val,
     switch ( reg )
     {
     case 0 ... 3:
-    case 6:
         *val = curr->arch.debugreg[reg];
         break;
 
+    case 4:
+        if ( curr->arch.pv.ctrlreg[4] & X86_CR4_DE )
+            goto ud_fault;
+
+        /* Fallthrough */
+    case 6:
+        *val = curr->arch.debugreg[6];
+        break;
+
+    case 5:
+        if ( curr->arch.pv.ctrlreg[4] & X86_CR4_DE )
+            goto ud_fault;
+
+        /* Fallthrough */
     case 7:
         *val = (curr->arch.debugreg[7] |
                 curr->arch.debugreg[5]);
         break;
 
-    case 4 ... 5:
-        if ( !(curr->arch.pv.ctrlreg[4] & X86_CR4_DE) )
-        {
-            *val = curr->arch.debugreg[reg + 2];
-            break;
-        }
-
-        /* Fallthrough */
+    ud_fault:
     default:
         if ( ctxt )
             x86_emul_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC, ctxt);