target-arm: Clean up handling of MPIDR

The ARM cp15 register 0,c0,c0,5 is standardised in the v7 architecture
as the MPIDR. Clean up its implementation to remove A9 specific handling.

This commit includes fixing an error in the value returned for the
MPIDR on A9, where we were erroneously claiming a cluster ID of 9.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

target-arm/helper.c

@@ -1608,12 +1608,28 @@ uint32_t HELPER(get_cp15)(CPUState *env, uint32_t insn)
                     return 0;
                 case 3: /* TLB type register.  */
                     return 0; /* No lockable TLB entries.  */
-                case 5: /* CPU ID */
-                    if (ARM_CPUID(env) == ARM_CPUID_CORTEXA9) {
-                        return env->cpu_index | 0x80000900;
-                    } else {
-                        return env->cpu_index;
+                case 5: /* MPIDR */
+                    /* The MPIDR was standardised in v7; prior to
+                     * this it was implemented only in the 11MPCore.
+                     * For all other pre-v7 cores it does not exist.
+                     */
+                    if (arm_feature(env, ARM_FEATURE_V7) ||
+                        ARM_CPUID(env) == ARM_CPUID_ARM11MPCORE) {
+                        int mpidr = env->cpu_index;
+                        /* We don't support setting cluster ID ([8..11])
+                         * so these bits always RAZ.
+                         */
+                        if (arm_feature(env, ARM_FEATURE_V7MP)) {
+                            mpidr |= (1 << 31);
+                            /* Cores which are uniprocessor (non-coherent)
+                             * but still implement the MP extensions set
+                             * bit 30. (For instance, A9UP.) However we do
+                             * not currently model any of those cores.
+                             */
+                        }
+                        return mpidr;
                     }
+                    /* otherwise fall through to the unimplemented-reg case */
                 default:
                     goto bad_reg;
                 }