diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 2532ec9739..9ba2f267f6 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -116,8 +116,8 @@ static void __init processor_id(void)
         printk("Huh, cpu architecture %x, expected 0xf (defined by cpuid)\n",
                c->midr.architecture);
 
-    printk("Processor: %08"PRIx32": \"%s\", variant: 0x%x, part 0x%03x, rev 0x%x\n",
-           c->midr.bits, implementer,
+    printk("Processor: %"PRIregister": \"%s\", variant: 0x%x, part 0x%03x,"
+           "rev 0x%x\n", c->midr.bits, implementer,
            c->midr.variant, c->midr.part_number, c->midr.revision);
 
 #if defined(CONFIG_ARM_64)
@@ -163,7 +163,7 @@ static void __init processor_id(void)
     if ( cpu_has_aarch32 )
     {
         printk("32-bit Execution:\n");
-        printk("  Processor Features: %08"PRIx32":%08"PRIx32"\n",
+        printk("  Processor Features: %"PRIregister":%"PRIregister"\n",
                boot_cpu_data.pfr32.bits[0], boot_cpu_data.pfr32.bits[1]);
         printk("    Instruction Sets:%s%s%s%s%s%s\n",
                cpu_has_aarch32 ? " AArch32" : "",
@@ -176,15 +176,16 @@ static void __init processor_id(void)
                cpu_has_gentimer ? " GenericTimer" : "",
                cpu_has_security ? " Security" : "");
 
-        printk("  Debug Features: %08"PRIx32"\n",
+        printk("  Debug Features: %"PRIregister"\n",
                boot_cpu_data.dbg32.bits[0]);
-        printk("  Auxiliary Features: %08"PRIx32"\n",
+        printk("  Auxiliary Features: %"PRIregister"\n",
                boot_cpu_data.aux32.bits[0]);
-        printk("  Memory Model Features: "
-               "%08"PRIx32" %08"PRIx32" %08"PRIx32" %08"PRIx32"\n",
+        printk("  Memory Model Features: %"PRIregister" %"PRIregister"\n"
+               "                         %"PRIregister" %"PRIregister"\n",
                boot_cpu_data.mm32.bits[0], boot_cpu_data.mm32.bits[1],
                boot_cpu_data.mm32.bits[2], boot_cpu_data.mm32.bits[3]);
-        printk(" ISA Features: %08x %08x %08x %08x %08x %08x\n",
+        printk("  ISA Features: %"PRIregister" %"PRIregister" %"PRIregister"\n"
+               "                %"PRIregister" %"PRIregister" %"PRIregister"\n",
                boot_cpu_data.isa32.bits[0], boot_cpu_data.isa32.bits[1],
                boot_cpu_data.isa32.bits[2], boot_cpu_data.isa32.bits[3],
                boot_cpu_data.isa32.bits[4], boot_cpu_data.isa32.bits[5]);
diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index cae2179126..a1ee3146ef 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -321,8 +321,9 @@ void start_secondary(void)
     if ( !opt_hmp_unsafe &&
          current_cpu_data.midr.bits != boot_cpu_data.midr.bits )
     {
-        printk(XENLOG_ERR "CPU%u MIDR (0x%x) does not match boot CPU MIDR (0x%x),\n"
-               "disable cpu (see big.LITTLE.txt under docs/).\n",
+        printk(XENLOG_ERR
+               "CPU%u MIDR (0x%"PRIregister") does not match boot CPU MIDR (0x%"PRIregister"),\n"
+               XENLOG_ERR "disable cpu (see big.LITTLE.txt under docs/).\n",
                smp_processor_id(), current_cpu_data.midr.bits,
                boot_cpu_data.midr.bits);
         stop_cpu();
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index 9ea3970c70..ba48db3eac 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -118,13 +118,16 @@ int enable_nonboot_cpu_caps(const struct arm_cpu_capabilities *caps);
  */
 struct cpuinfo_arm {
     union {
-        uint32_t bits;
+        register_t bits;
         struct {
             unsigned long revision:4;
             unsigned long part_number:12;
             unsigned long architecture:4;
             unsigned long variant:4;
             unsigned long implementer:8;
+#ifdef CONFIG_ARM_64
+            unsigned long _res0:32;
+#endif
         };
     } midr;
     union {
@@ -148,7 +151,7 @@ struct cpuinfo_arm {
 #ifdef CONFIG_ARM_64
     /* 64-bit CPUID registers. */
     union {
-        uint64_t bits[2];
+        register_t bits[2];
         struct {
             /* PFR0 */
             unsigned long el0:4;
@@ -179,15 +182,15 @@ struct cpuinfo_arm {
     } pfr64;
 
     struct {
-        uint64_t bits[2];
+        register_t bits[2];
     } dbg64;
 
     struct {
-        uint64_t bits[2];
+        register_t bits[2];
     } aux64;
 
     union {
-        uint64_t bits[3];
+        register_t bits[3];
         struct {
             unsigned long pa_range:4;
             unsigned long asid_bits:4;
@@ -213,7 +216,7 @@ struct cpuinfo_arm {
     } mm64;
 
     union {
-        uint64_t bits[2];
+        register_t bits[2];
         struct {
             /* ISAR0 */
             unsigned long __res0:4;
@@ -263,7 +266,7 @@ struct cpuinfo_arm {
      * when running in 32-bit mode.
      */
     union {
-        uint32_t bits[3];
+        register_t bits[3];
         struct {
             /* PFR0 */
             unsigned long arm:4;
@@ -274,6 +277,9 @@ struct cpuinfo_arm {
             unsigned long amu:4;
             unsigned long dit:4;
             unsigned long ras:4;
+#ifdef CONFIG_ARM_64
+            unsigned long __res0:32;
+#endif
 
             /* PFR1 */
             unsigned long progmodel:4;
@@ -284,29 +290,35 @@ struct cpuinfo_arm {
             unsigned long sec_frac:4;
             unsigned long virt_frac:4;
             unsigned long gic:4;
+#ifdef CONFIG_ARM_64
+            unsigned long __res1:32;
+#endif
 
             /* PFR2 */
             unsigned long csv3:4;
             unsigned long ssbs:4;
             unsigned long ras_frac:4;
             unsigned long __res2:20;
+#ifdef CONFIG_ARM_64
+            unsigned long __res3:32;
+#endif
         };
     } pfr32;
 
     struct {
-        uint32_t bits[2];
+        register_t bits[2];
     } dbg32;
 
     struct {
-        uint32_t bits[1];
+        register_t bits[1];
     } aux32;
 
     struct {
-        uint32_t bits[6];
+        register_t bits[6];
     } mm32;
 
     struct {
-        uint32_t bits[7];
+        register_t bits[7];
     } isa32;
 
     struct {