target-arm: Implement TTBCR changes for LPAE

Implement the changes to the TTBCR register required for LPAE:
 * many fewer bits should be RAZ/WI
 * since TTBCR changes can result in a change of ASID, we must
   flush the TLB on writes to it
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/helper.c

@@ -692,7 +692,20 @@ static const ARMCPRegInfo pmsav5_cp_reginfo[] = {
 static int vmsa_ttbcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
                             uint64_t value)
 {
-    value &= 7;
+    if (arm_feature(env, ARM_FEATURE_LPAE)) {
+        value &= ~((7 << 19) | (3 << 14) | (0xf << 3));
+        /* With LPAE the TTBCR could result in a change of ASID
+         * via the TTBCR.A1 bit, so do a TLB flush.
+         */
+        tlb_flush(env, 1);
+    } else {
+        value &= 7;
+    }
+    /* Note that we always calculate c2_mask and c2_base_mask, but
+     * they are only used for short-descriptor tables (ie if EAE is 0);
+     * for long-descriptor tables the TTBCR fields are used differently
+     * and the c2_mask and c2_base_mask values are meaningless.
+     */
     env->cp15.c2_control = value;
     env->cp15.c2_mask = ~(((uint32_t)0xffffffffu) >> value);
     env->cp15.c2_base_mask = ~((uint32_t)0x3fffu >> value);