diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index d5d0792ed4..6b88320588 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -1048,6 +1048,9 @@ void __init start_xen(unsigned long boot_phys_offset,
     /* Hide UART from DOM0 if we're using it */
     serial_endboot();
 
+    if ( (rc = xsm_set_system_active()) != 0 )
+        panic("xsm: unable to switch to SYSTEM_ACTIVE privilege: %d\n", rc);
+
     system_state = SYS_STATE_active;
 
     for_each_domain( d )
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 6f20e17892..962da03f80 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -620,6 +620,10 @@ static void noreturn init_done(void)
 {
     void *va;
     unsigned long start, end;
+    int err;
+
+    if ( (err = xsm_set_system_active()) != 0 )
+        panic("xsm: unable to switch to SYSTEM_ACTIVE privilege: %d\n", err);
 
     system_state = SYS_STATE_active;
 
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 19ab678181..7b1c03a0e1 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -3021,7 +3021,12 @@ void __init scheduler_init(void)
         sched_ratelimit_us = SCHED_DEFAULT_RATELIMIT_US;
     }
 
-    idle_domain = domain_create(DOMID_IDLE, NULL, 0);
+    /*
+     * The idle dom is created privileged to ensure unrestricted access during
+     * setup and will be demoted by xsm_set_system_active() when setup is
+     * complete.
+     */
+    idle_domain = domain_create(DOMID_IDLE, NULL, CDF_privileged);
     BUG_ON(IS_ERR(idle_domain));
     BUG_ON(nr_cpu_ids > ARRAY_SIZE(idle_vcpu));
     idle_domain->vcpu = idle_vcpu;
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 58afc1d589..77f27e7163 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -101,6 +101,23 @@ static always_inline int xsm_default_action(
     }
 }
 
+static XSM_INLINE int cf_check xsm_set_system_active(void)
+{
+    struct domain *d = current->domain;
+
+    ASSERT(d->is_privileged);
+
+    if ( d->domain_id != DOMID_IDLE )
+    {
+        printk("%s: should only be called by idle domain\n", __func__);
+        return -EPERM;
+    }
+
+    d->is_privileged = false;
+
+    return 0;
+}
+
 static XSM_INLINE void cf_check xsm_security_domaininfo(
     struct domain *d, struct xen_domctl_getdomaininfo *info)
 {
diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
index 3e2b7fe3db..8dad03fd3d 100644
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -52,6 +52,7 @@ typedef enum xsm_default xsm_default_t;
  * !!! WARNING !!!
  */
 struct xsm_ops {
+    int (*set_system_active)(void);
     void (*security_domaininfo)(struct domain *d,
                                 struct xen_domctl_getdomaininfo *info);
     int (*domain_create)(struct domain *d, uint32_t ssidref);
@@ -208,6 +209,11 @@ extern struct xsm_ops xsm_ops;
 
 #ifndef XSM_NO_WRAPPERS
 
+static inline int xsm_set_system_active(void)
+{
+    return alternative_call(xsm_ops.set_system_active);
+}
+
 static inline void xsm_security_domaininfo(
     struct domain *d, struct xen_domctl_getdomaininfo *info)
 {
diff --git a/xen/xsm/dummy.c b/xen/xsm/dummy.c
index 8c044ef615..e6ffa948f7 100644
--- a/xen/xsm/dummy.c
+++ b/xen/xsm/dummy.c
@@ -14,6 +14,7 @@
 #include <xsm/dummy.h>
 
 static const struct xsm_ops __initconst_cf_clobber dummy_ops = {
+    .set_system_active             = xsm_set_system_active,
     .security_domaininfo           = xsm_security_domaininfo,
     .domain_create                 = xsm_domain_create,
     .getdomaininfo                 = xsm_getdomaininfo,
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 0bf63ffa84..06ca4e7a91 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -186,6 +186,28 @@ static int cf_check flask_domain_alloc_security(struct domain *d)
     return 0;
 }
 
+static int cf_check flask_set_system_active(void)
+{
+    struct domain *d = current->domain;
+
+    ASSERT(d->is_privileged);
+
+    if ( d->domain_id != DOMID_IDLE )
+    {
+        printk("%s: should only be called by idle domain\n", __func__);
+        return -EPERM;
+    }
+
+    /*
+     * While is_privileged has no significant meaning under flask, set to false
+     * as is_privileged is not only used for a privilege check but also as a
+     * type of domain check, specifically if the domain is the control domain.
+     */
+    d->is_privileged = false;
+
+    return 0;
+}
+
 static void cf_check flask_domain_free_security(struct domain *d)
 {
     struct domain_security_struct *dsec = d->ssid;
@@ -1766,6 +1788,7 @@ static int cf_check flask_argo_send(
 #endif
 
 static const struct xsm_ops __initconst_cf_clobber flask_ops = {
+    .set_system_active = flask_set_system_active,
     .security_domaininfo = flask_security_domaininfo,
     .domain_create = flask_domain_create,
     .getdomaininfo = flask_getdomaininfo,
