diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 2b52eb77e29c..5fe84f2427b5 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1000,6 +1000,10 @@ blobs in userspace.  When the guest writes the MSR, kvm copies one
 page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
 memory.
 
+The MSR index must be in the range [0x40000000, 0x4fffffff], i.e. must reside
+in the range that is unofficially reserved for use by hypervisors.  The min/max
+values are enumerated via KVM_XEN_MSR_MIN_INDEX and KVM_XEN_MSR_MAX_INDEX.
+
 ::
 
   struct kvm_xen_hvm_config {
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 9e75da97bce0..460306b35a4b 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -559,6 +559,9 @@ struct kvm_x86_mce {
 #define KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE	(1 << 7)
 #define KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA	(1 << 8)
 
+#define KVM_XEN_MSR_MIN_INDEX			0x40000000u
+#define KVM_XEN_MSR_MAX_INDEX			0x4fffffffu
+
 struct kvm_xen_hvm_config {
 	__u32 flags;
 	__u32 msr;
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index a909b817b9c0..5b94825001a7 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1324,6 +1324,15 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc)
 	     xhc->blob_size_32 || xhc->blob_size_64))
 		return -EINVAL;
 
+	/*
+	 * Restrict the MSR to the range that is unofficially reserved for
+	 * synthetic, virtualization-defined MSRs, e.g. to prevent confusing
+	 * KVM by colliding with a real MSR that requires special handling.
+	 */
+	if (xhc->msr &&
+	    (xhc->msr < KVM_XEN_MSR_MIN_INDEX || xhc->msr > KVM_XEN_MSR_MAX_INDEX))
+		return -EINVAL;
+
 	mutex_lock(&kvm->arch.xen.xen_lock);
 
 	if (xhc->msr && !kvm->arch.xen_hvm_config.msr)