diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 111a2029e6..54e66a86d0 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -919,7 +919,7 @@ static void _show_registers(const struct cpu_user_regs *regs,
 #ifdef CONFIG_ARM_64
         else if ( is_64bit_domain(v->domain) )
         {
-            if ( psr_mode_is_32bit(regs->cpsr) )
+            if ( psr_mode_is_32bit(regs) )
             {
                 BUG_ON(!usr_mode(regs));
                 show_registers_32(regs, ctxt, guest_mode, v);
@@ -1625,7 +1625,7 @@ int check_conditional_instr(struct cpu_user_regs *regs, const union hsr hsr)
     {
         unsigned long it;
 
-        BUG_ON( !psr_mode_is_32bit(regs->cpsr) || !(cpsr&PSR_THUMB) );
+        BUG_ON( !psr_mode_is_32bit(regs) || !(cpsr & PSR_THUMB) );
 
         it = ( (cpsr >> (10-2)) & 0xfc) | ((cpsr >> 25) & 0x3 );
 
@@ -1650,7 +1650,7 @@ int check_conditional_instr(struct cpu_user_regs *regs, const union hsr hsr)
 void advance_pc(struct cpu_user_regs *regs, const union hsr hsr)
 {
     unsigned long itbits, cond, cpsr = regs->cpsr;
-    bool is_thumb = psr_mode_is_32bit(cpsr) && (cpsr & PSR_THUMB);
+    bool is_thumb = psr_mode_is_32bit(regs) && (cpsr & PSR_THUMB);
 
     if ( is_thumb && (cpsr & PSR_IT_MASK) )
     {
@@ -2078,32 +2078,32 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
         advance_pc(regs, hsr);
         break;
     case HSR_EC_CP15_32:
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_cp15_32);
         do_cp15_32(regs, hsr);
         break;
     case HSR_EC_CP15_64:
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_cp15_64);
         do_cp15_64(regs, hsr);
         break;
     case HSR_EC_CP14_32:
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_cp14_32);
         do_cp14_32(regs, hsr);
         break;
     case HSR_EC_CP14_64:
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_cp14_64);
         do_cp14_64(regs, hsr);
         break;
     case HSR_EC_CP14_DBG:
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_cp14_dbg);
         do_cp14_dbg(regs, hsr);
         break;
     case HSR_EC_CP:
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_cp);
         do_cp(regs, hsr);
         break;
@@ -2114,7 +2114,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
          * ARMv7 (DDI 0406C.b): B1.14.8
          * ARMv8 (DDI 0487A.d): D1-1501 Table D1-44
          */
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_smc32);
         do_trap_smc(regs, hsr);
         break;
@@ -2122,7 +2122,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
     {
         register_t nr;
 
-        GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(!psr_mode_is_32bit(regs));
         perfc_incr(trap_hvc32);
 #ifndef NDEBUG
         if ( (hsr.iss & 0xff00) == 0xff00 )
@@ -2137,7 +2137,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
     }
 #ifdef CONFIG_ARM_64
     case HSR_EC_HVC64:
-        GUEST_BUG_ON(psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(psr_mode_is_32bit(regs));
         perfc_incr(trap_hvc64);
 #ifndef NDEBUG
         if ( (hsr.iss & 0xff00) == 0xff00 )
@@ -2153,12 +2153,12 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
          *
          * ARMv8 (DDI 0487A.d): D1-1501 Table D1-44
          */
-        GUEST_BUG_ON(psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(psr_mode_is_32bit(regs));
         perfc_incr(trap_smc64);
         do_trap_smc(regs, hsr);
         break;
     case HSR_EC_SYSREG:
-        GUEST_BUG_ON(psr_mode_is_32bit(regs->cpsr));
+        GUEST_BUG_ON(psr_mode_is_32bit(regs));
         perfc_incr(trap_sysreg);
         do_sysreg(regs, hsr);
         break;
diff --git a/xen/include/asm-arm/regs.h b/xen/include/asm-arm/regs.h
index ddc6eba9ce..0e3e56b452 100644
--- a/xen/include/asm-arm/regs.h
+++ b/xen/include/asm-arm/regs.h
@@ -13,7 +13,14 @@
 
 #define psr_mode(psr,m) (((psr) & PSR_MODE_MASK) == m)
 
-#define psr_mode_is_32bit(psr) !!((psr) & PSR_MODE_BIT)
+static inline bool psr_mode_is_32bit(const struct cpu_user_regs *regs)
+{
+#ifdef CONFIG_ARM_32
+    return true;
+#else
+    return !!(regs->cpsr & PSR_MODE_BIT);
+#endif
+}
 
 #define usr_mode(r)     psr_mode((r)->cpsr,PSR_MODE_USR)
 #define fiq_mode(r)     psr_mode((r)->cpsr,PSR_MODE_FIQ)
