target/arm: Implement HCR.PTW

If the HCR_EL2 PTW virtualizaiton configuration register bit
is set, then this means that a stage 2 Permission fault must
be generated if a stage 1 translation table access is made
to an address that is mapped as Device memory in stage 2.
Implement this.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20181012144235.19646-8-peter.maydell@linaro.org

target/arm/helper.c

@@ -9141,9 +9141,20 @@ static hwaddr S1_ptw_translate(CPUARMState *env, ARMMMUIdx mmu_idx,
         hwaddr s2pa;
         int s2prot;
         int ret;
+        ARMCacheAttrs cacheattrs = {};
+        ARMCacheAttrs *pcacheattrs = NULL;
+
+        if (env->cp15.hcr_el2 & HCR_PTW) {
+            /*
+             * PTW means we must fault if this S1 walk touches S2 Device
+             * memory; otherwise we don't care about the attributes and can
+             * save the S2 translation the effort of computing them.
+             */
+            pcacheattrs = &cacheattrs;
+        }
 
         ret = get_phys_addr_lpae(env, addr, 0, ARMMMUIdx_S2NS, &s2pa,
-                                 &txattrs, &s2prot, &s2size, fi, NULL);
+                                 &txattrs, &s2prot, &s2size, fi, pcacheattrs);
         if (ret) {
             assert(fi->type != ARMFault_None);
             fi->s2addr = addr;
@@ -9151,6 +9162,14 @@ static hwaddr S1_ptw_translate(CPUARMState *env, ARMMMUIdx mmu_idx,
             fi->s1ptw = true;
             return ~0;
         }
+        if (pcacheattrs && (pcacheattrs->attrs & 0xf0) == 0) {
+            /* Access was to Device memory: generate Permission fault */
+            fi->type = ARMFault_Permission;
+            fi->s2addr = addr;
+            fi->stage2 = true;
+            fi->s1ptw = true;
+            return ~0;
+        }
         addr = s2pa;
     }
     return addr;