diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index 49d57469fb..ad20584f26 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -1101,7 +1101,7 @@ clk_setup_cb cpu_ppc_tb_init (CPUPPCState *env, uint32_t freq)
     tb_env = g_malloc0(sizeof(ppc_tb_t));
     env->tb_env = tb_env;
     tb_env->flags = PPC_DECR_UNDERFLOW_TRIGGERED;
-    if (env->insns_flags & PPC_SEGMENT_64B) {
+    if (is_book3s_arch2x(env)) {
         /* All Book3S 64bit CPUs implement level based DEC logic */
         tb_env->flags |= PPC_DECR_UNDERFLOW_LEVEL;
     }
diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index fc12b4688e..0707177584 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -2409,6 +2409,12 @@ enum {
 target_ulong cpu_read_xer(CPUPPCState *env);
 void cpu_write_xer(CPUPPCState *env, target_ulong xer);
 
+/*
+ * All 64-bit server processors compliant with arch 2.x, ie. 970 and newer,
+ * have PPC_SEGMENT_64B.
+ */
+#define is_book3s_arch2x(ctx) (!!((ctx)->insns_flags & PPC_SEGMENT_64B))
+
 static inline void cpu_get_tb_cpu_state(CPUPPCState *env, target_ulong *pc,
                                         target_ulong *cs_base, uint32_t *flags)
 {
diff --git a/target/ppc/helper_regs.h b/target/ppc/helper_regs.h
index a2205e1044..c863abc0bf 100644
--- a/target/ppc/helper_regs.h
+++ b/target/ppc/helper_regs.h
@@ -152,7 +152,7 @@ static inline int hreg_store_msr(CPUPPCState *env, target_ulong value,
      * - 64-bit embedded implementations do not need any operation to be
      *   performed when PR is set.
      */
-    if ((env->insns_flags & PPC_SEGMENT_64B) && ((value >> MSR_PR) & 1)) {
+    if (is_book3s_arch2x(env) && ((value >> MSR_PR) & 1)) {
         value |= (1 << MSR_EE) | (1 << MSR_DR) | (1 << MSR_IR);
     }
 #endif
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index d3aaa6482c..576210d901 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -3755,7 +3755,7 @@ static void gen_bcond(DisasContext *ctx, int type)
              * arch 2.x, do implement a "test and decrement" logic instead,
              * as described in their respective UMs.
              */
-            if (unlikely(!(ctx->insns_flags & PPC_SEGMENT_64B))) {
+            if (unlikely(!is_book3s_arch2x(ctx))) {
                 gen_inval_exception(ctx, POWERPC_EXCP_INVAL_INVAL);
                 tcg_temp_free(temp);
                 tcg_temp_free(target);
@@ -3913,7 +3913,7 @@ static void gen_rfi(DisasContext *ctx)
     /* This instruction doesn't exist anymore on 64-bit server
      * processors compliant with arch 2.x
      */
-    if (ctx->insns_flags & PPC_SEGMENT_64B) {
+    if (is_book3s_arch2x(ctx)) {
         gen_inval_exception(ctx, POWERPC_EXCP_INVAL_INVAL);
         return;
     }
@@ -6535,8 +6535,7 @@ static void gen_msgclr(DisasContext *ctx)
     GEN_PRIV;
 #else
     CHK_HV;
-    /* 64-bit server processors compliant with arch 2.x */
-    if (ctx->insns_flags & PPC_SEGMENT_64B) {
+    if (is_book3s_arch2x(ctx)) {
         gen_helper_book3s_msgclr(cpu_env, cpu_gpr[rB(ctx->opcode)]);
     } else {
         gen_helper_msgclr(cpu_env, cpu_gpr[rB(ctx->opcode)]);
@@ -6550,8 +6549,7 @@ static void gen_msgsnd(DisasContext *ctx)
     GEN_PRIV;
 #else
     CHK_HV;
-    /* 64-bit server processors compliant with arch 2.x */
-    if (ctx->insns_flags & PPC_SEGMENT_64B) {
+    if (is_book3s_arch2x(ctx)) {
         gen_helper_book3s_msgsnd(cpu_gpr[rB(ctx->opcode)]);
     } else {
         gen_helper_msgsnd(cpu_gpr[rB(ctx->opcode)]);