target-arm: Allow cp access functions to indicate traps to EL2 or EL3

Some coprocessor access functions will need to indicate that the
instruction should trap to EL2 or EL3 rather than the default
target exception level; add corresponding CPAccessResult enum
entries and handling code.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>

target-arm/cpu.h

@@ -1252,7 +1252,8 @@ typedef enum CPAccessResult {
     /* Access fails due to a configurable trap or enable which would
      * result in a categorized exception syndrome giving information about
      * the failing instruction (ie syndrome category 0x3, 0x4, 0x5, 0x6,
-     * 0xc or 0x18).
+     * 0xc or 0x18). The exception is taken to the usual target EL (EL1 or
+     * PL1 if in EL0, otherwise to the current EL).
      */
     CP_ACCESS_TRAP = 1,
     /* Access fails and results in an exception syndrome 0x0 ("uncategorized").
@@ -1260,6 +1261,9 @@ typedef enum CPAccessResult {
      * result in this failure is specifically defined by the architecture.
      */
     CP_ACCESS_TRAP_UNCATEGORIZED = 2,
+    /* As CP_ACCESS_TRAP, but for traps directly to EL2 or EL3 */
+    CP_ACCESS_TRAP_EL2 = 3,
+    CP_ACCESS_TRAP_EL3 = 4,
 } CPAccessResult;
 
 /* Access functions for coprocessor registers. These cannot fail and

target-arm/op_helper.c

@@ -335,6 +335,7 @@ void HELPER(set_user_reg)(CPUARMState *env, uint32_t regno, uint32_t val)
 void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome)
 {
     const ARMCPRegInfo *ri = rip;
+    int target_el;
 
     if (arm_feature(env, ARM_FEATURE_XSCALE) && ri->cp < 14
         && extract32(env->cp15.c15_cpar, ri->cp, 1) == 0) {
@@ -349,15 +350,27 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome)
     case CP_ACCESS_OK:
         return;
     case CP_ACCESS_TRAP:
+        target_el = exception_target_el(env);
+        break;
+    case CP_ACCESS_TRAP_EL2:
+        /* Requesting a trap to EL2 when we're in EL3 or S-EL0/1 is
+         * a bug in the access function.
+         */
+        assert(!arm_is_secure(env) && !arm_current_el(env) == 3);
+        target_el = 2;
+        break;
+    case CP_ACCESS_TRAP_EL3:
+        target_el = 3;
         break;
     case CP_ACCESS_TRAP_UNCATEGORIZED:
+        target_el = exception_target_el(env);
         syndrome = syn_uncategorized();
         break;
     default:
         g_assert_not_reached();
     }
 
-    raise_exception(env, EXCP_UDEF, syndrome, exception_target_el(env));
+    raise_exception(env, EXCP_UDEF, syndrome, target_el);
 }
 
 void HELPER(set_cp_reg)(CPUARMState *env, void *rip, uint32_t value)