target/arm: Don't do MPU lookups for addresses in M profile PPB region

The M profile PMSAv7 specification says that if the address being looked
up is in the PPB region (0xe0000000 - 0xe00fffff) then we do not use
the MPU regions but always use the default memory map. Implement this
(we were previously behaving like an R profile PMSAv7, which does not
special case this).
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 1501153150-19984-2-git-send-email-peter.maydell@linaro.org

target/arm/helper.c

@@ -8244,6 +8244,13 @@ static bool pmsav7_use_background_region(ARMCPU *cpu,
     }
 }
 
+static inline bool m_is_ppb_region(CPUARMState *env, uint32_t address)
+{
+    /* True if address is in the M profile PPB region 0xe0000000 - 0xe00fffff */
+    return arm_feature(env, ARM_FEATURE_M) &&
+        extract32(address, 20, 12) == 0xe00;
+}
+
 static bool get_phys_addr_pmsav7(CPUARMState *env, uint32_t address,
                                  int access_type, ARMMMUIdx mmu_idx,
                                  hwaddr *phys_ptr, int *prot, uint32_t *fsr)
@@ -8255,7 +8262,15 @@ static bool get_phys_addr_pmsav7(CPUARMState *env, uint32_t address,
     *phys_ptr = address;
     *prot = 0;
 
-    if (regime_translation_disabled(env, mmu_idx)) { /* MPU disabled */
+    if (regime_translation_disabled(env, mmu_idx) ||
+        m_is_ppb_region(env, address)) {
+        /* MPU disabled or M profile PPB access: use default memory map.
+         * The other case which uses the default memory map in the
+         * v7M ARM ARM pseudocode is exception vector reads from the vector
+         * table. In QEMU those accesses are done in arm_v7m_load_vector(),
+         * which always does a direct read using address_space_ldl(), rather
+         * than going via this function, so we don't need to check that here.
+         */
         get_phys_addr_pmsav7_default(env, mmu_idx, address, prot);
     } else { /* MPU enabled */
         for (n = (int)cpu->pmsav7_dregion - 1; n >= 0; n--) {