diff --git a/xen/arch/x86/x86_64/domain.c b/xen/arch/x86/x86_64/domain.c
index a02d4f569e..533b0b21a0 100644
--- a/xen/arch/x86/x86_64/domain.c
+++ b/xen/arch/x86/x86_64/domain.c
@@ -58,6 +58,11 @@ compat_vcpu_op(int cmd, unsigned int vcpuid, XEN_GUEST_HANDLE_PARAM(void) arg)
         rc = 0;
         guest_from_compat_handle(v->runstate_guest.compat, area.addr.h);
 
+        /* NULL handle is deregistering the address. */
+        if ( compat_handle_is_null(area.addr.h) )
+            break;
+
+        /* Update the newly-registered runstate area, best-effort. */
         if ( v == current )
         {
             XLAT_vcpu_runstate_info(&info, &v->runstate);
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 6b52713518..b41be89cd0 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -2324,12 +2324,21 @@ long common_vcpu_op(int cmd, struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( copy_from_guest(&area, arg, 1) )
             break;
 
+        /* NULL handle is deregistering the address. */
+        if ( guest_handle_is_null(area.addr.h) )
+        {
+            runstate_guest(v) = area.addr.h;
+            rc = 0;
+            break;
+        }
+
         if ( !guest_handle_okay(area.addr.h, 1) )
             break;
 
         rc = 0;
         runstate_guest(v) = area.addr.h;
 
+        /* Update the newly-registered runstate area, best-effort. */
         if ( v == current )
         {
             __copy_to_guest(runstate_guest(v), &v->runstate, 1);
diff --git a/xen/include/public/vcpu.h b/xen/include/public/vcpu.h
index 5aea6ca709..9a8003e3ec 100644
--- a/xen/include/public/vcpu.h
+++ b/xen/include/public/vcpu.h
@@ -112,6 +112,7 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_runstate_info_t);
  *     VCPU was last scheduled to run.
  *  3. New code wants to prefer VCPUOP_register_runstate_phys_area, and only
  *     fall back to the operation here for backwards compatibility.
+ *  4. Passing a NULL handle will deregister the region.
  * @extra_arg == pointer to vcpu_register_runstate_memory_area structure.
  */
 #define VCPUOP_register_runstate_memory_area 5