target/arm: Adjust sve_exception_el

Check for EL3 before testing CPTR_EL3.EZ.  Return 0 when the exception
should be routed via AdvSIMDFPAccessTrap.  Mirror the structure of
CheckSVEEnabled more closely.

Fixes: 5be5e8e
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181005175350.30752-3-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -4400,67 +4400,63 @@ static const ARMCPRegInfo debug_lpae_cp_reginfo[] = {
     REGINFO_SENTINEL
 };
 
-/* Return the exception level to which SVE-disabled exceptions should
- * be taken, or 0 if SVE is enabled.
+/* Return the exception level to which exceptions should be taken
+ * via SVEAccessTrap.  If an exception should be routed through
+ * AArch64.AdvSIMDFPAccessTrap, return 0; fp_exception_el should
+ * take care of raising that exception.
+ * C.f. the ARM pseudocode function CheckSVEEnabled.
  */
 static int sve_exception_el(CPUARMState *env)
 {
 #ifndef CONFIG_USER_ONLY
     unsigned current_el = arm_current_el(env);
 
-    /* The CPACR.ZEN controls traps to EL1:
-     * 0, 2 : trap EL0 and EL1 accesses
-     * 1    : trap only EL0 accesses
-     * 3    : trap no accesses
-     */
-    switch (extract32(env->cp15.cpacr_el1, 16, 2)) {
-    default:
-        if (current_el <= 1) {
-            /* Trap to PL1, which might be EL1 or EL3 */
-            if (arm_is_secure(env) && !arm_el_is_aa64(env, 3)) {
-                return 3;
-            }
-            return 1;
+    if (current_el <= 1) {
+        bool disabled = false;
+
+        /* The CPACR.ZEN controls traps to EL1:
+         * 0, 2 : trap EL0 and EL1 accesses
+         * 1    : trap only EL0 accesses
+         * 3    : trap no accesses
+         */
+        if (!extract32(env->cp15.cpacr_el1, 16, 1)) {
+            disabled = true;
+        } else if (!extract32(env->cp15.cpacr_el1, 17, 1)) {
+            disabled = current_el == 0;
         }
-        break;
-    case 1:
-        if (current_el == 0) {
-            return 1;
+        if (disabled) {
+            /* route_to_el2 */
+            return (arm_feature(env, ARM_FEATURE_EL2)
+                    && !arm_is_secure(env)
+                    && (env->cp15.hcr_el2 & HCR_TGE) ? 2 : 1);
         }
-        break;
-    case 3:
-        break;
-    }
 
-    /* Similarly for CPACR.FPEN, after having checked ZEN.  */
-    switch (extract32(env->cp15.cpacr_el1, 20, 2)) {
-    default:
-        if (current_el <= 1) {
-            if (arm_is_secure(env) && !arm_el_is_aa64(env, 3)) {
-                return 3;
-            }
-            return 1;
+        /* Check CPACR.FPEN.  */
+        if (!extract32(env->cp15.cpacr_el1, 20, 1)) {
+            disabled = true;
+        } else if (!extract32(env->cp15.cpacr_el1, 21, 1)) {
+            disabled = current_el == 0;
         }
-        break;
-    case 1:
-        if (current_el == 0) {
-            return 1;
+        if (disabled) {
+            return 0;
         }
-        break;
-    case 3:
-        break;
     }
 
-    /* CPTR_EL2.  Check both TZ and TFP.  */
-    if (current_el <= 2
-        && (env->cp15.cptr_el[2] & (CPTR_TFP | CPTR_TZ))
-        && !arm_is_secure_below_el3(env)) {
-        return 2;
+    /* CPTR_EL2.  Since TZ and TFP are positive,
+     * they will be zero when EL2 is not present.
+     */
+    if (current_el <= 2 && !arm_is_secure_below_el3(env)) {
+        if (env->cp15.cptr_el[2] & CPTR_TZ) {
+            return 2;
+        }
+        if (env->cp15.cptr_el[2] & CPTR_TFP) {
+            return 0;
+        }
     }
 
-    /* CPTR_EL3.  Check both EZ and TFP.  */
-    if (!(env->cp15.cptr_el[3] & CPTR_EZ)
-        || (env->cp15.cptr_el[3] & CPTR_TFP)) {
+    /* CPTR_EL3.  Since EZ is negative we must check for EL3.  */
+    if (arm_feature(env, ARM_FEATURE_EL3)
+        && !(env->cp15.cptr_el[3] & CPTR_EZ)) {
         return 3;
     }
 #endif