diff --git a/xen/arch/Kconfig b/xen/arch/Kconfig
index 308ce129a8..9f4835e37f 100644
--- a/xen/arch/Kconfig
+++ b/xen/arch/Kconfig
@@ -6,8 +6,10 @@ config PHYS_ADDR_T_32
 
 config NR_CPUS
 	int "Maximum number of CPUs"
+	range 1 1 if ARM && MPU
 	range 1 16383
 	default "256" if X86
+	default "1" if ARM && MPU
 	default "8" if ARM && RCAR3
 	default "4" if ARM && QEMU
 	default "4" if ARM && MPSOC
diff --git a/xen/arch/arm/arm64/mpu/head.S b/xen/arch/arm/arm64/mpu/head.S
index bacf8315f9..d3db5e53af 100644
--- a/xen/arch/arm/arm64/mpu/head.S
+++ b/xen/arch/arm/arm64/mpu/head.S
@@ -144,6 +144,16 @@ FUNC(enable_boot_cpu_mm)
     ret
 END(enable_boot_cpu_mm)
 
+/*
+ * We don't yet support secondary CPUs bring-up. Implement a dummy helper to
+ * please the common code.
+ */
+ENTRY(enable_secondary_cpu_mm)
+    PRINT("- SMP not enabled yet -\r\n")
+1:  wfe
+    b 1b
+ENDPROC(enable_secondary_cpu_mm)
+
 /*
  * Local variables:
  * mode: ASM
diff --git a/xen/arch/arm/smp.c b/xen/arch/arm/smp.c
index c11bba93ad..b372472188 100644
--- a/xen/arch/arm/smp.c
+++ b/xen/arch/arm/smp.c
@@ -1,4 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
+#include <xen/init.h>
 #include <xen/mm.h>
 #include <asm/system.h>
 #include <asm/smp.h>
@@ -6,6 +7,16 @@
 #include <asm/gic.h>
 #include <asm/flushtlb.h>
 
+static void __init __maybe_unused build_assertions(void)
+{
+#ifdef CONFIG_MPU
+    /*
+     * Currently, SMP is not enabled on MPU based systems.
+     */
+    BUILD_BUG_ON(NR_CPUS > 1);
+#endif
+}
+
 void arch_flush_tlb_mask(const cpumask_t *mask)
 {
     /* No need to IPI other processors on ARM, the processor takes care of it. */