target-arm: correct CNTFRQ access rights

Correct some corner cases we were getting wrong for
CNTFRQ access rights:
 * should UNDEF from 32-bit Secure EL1
 * only writable from the highest implemented exception level,
   which might not be EL1 now

To clarify the code, provide a new utility function
arm_highest_el() which returns the highest implemented
exception level.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 5137632..afbf366 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -1255,6 +1255,18 @@ static inline bool cptype_valid(int cptype)
 #define PL1_RW (PL1_R | PL1_W)
 #define PL0_RW (PL0_R | PL0_W)
 
+/* Return the highest implemented Exception Level */
+static inline int arm_highest_el(CPUARMState *env)
+{
+    if (arm_feature(env, ARM_FEATURE_EL3)) {
+        return 3;
+    }
+    if (arm_feature(env, ARM_FEATURE_EL2)) {
+        return 2;
+    }
+    return 1;
+}
+
 /* Return the current Exception Level (as per ARMv8; note that this differs
  * from the ARMv7 Privilege Level).
  */