diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 64b14ac4c7b02..fc8c1420c0b69 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -2368,6 +2368,13 @@ static int dmar_device_hotplug(acpi_handle handle, bool insert)
 	if (!dmar_in_use())
 		return 0;
 
+	/*
+	 * It's unlikely that any I/O board is hot added before the IOMMU
+	 * subsystem is initialized.
+	 */
+	if (IS_ENABLED(CONFIG_INTEL_IOMMU) && !intel_iommu_enabled)
+		return -EOPNOTSUPP;
+
 	if (dmar_detect_dsm(handle, DMAR_DSM_FUNC_DRHD)) {
 		tmp = handle;
 	} else {
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 5c0dce78586aa..936def2f416a2 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3123,13 +3123,7 @@ static int __init init_dmars(void)
 
 #ifdef CONFIG_INTEL_IOMMU_SVM
 		if (pasid_supported(iommu) && ecap_prs(iommu->ecap)) {
-			/*
-			 * Call dmar_alloc_hwirq() with dmar_global_lock held,
-			 * could cause possible lock race condition.
-			 */
-			up_write(&dmar_global_lock);
 			ret = intel_svm_enable_prq(iommu);
-			down_write(&dmar_global_lock);
 			if (ret)
 				goto free_iommu;
 		}
@@ -4035,7 +4029,6 @@ int __init intel_iommu_init(void)
 	force_on = (!intel_iommu_tboot_noforce && tboot_force_iommu()) ||
 		    platform_optin_force_iommu();
 
-	down_write(&dmar_global_lock);
 	if (dmar_table_init()) {
 		if (force_on)
 			panic("tboot: Failed to initialize DMAR table\n");
@@ -4048,16 +4041,6 @@ int __init intel_iommu_init(void)
 		goto out_free_dmar;
 	}
 
-	up_write(&dmar_global_lock);
-
-	/*
-	 * The bus notifier takes the dmar_global_lock, so lockdep will
-	 * complain later when we register it under the lock.
-	 */
-	dmar_register_bus_notifier();
-
-	down_write(&dmar_global_lock);
-
 	if (!no_iommu)
 		intel_iommu_debugfs_init();
 
@@ -4105,11 +4088,9 @@ int __init intel_iommu_init(void)
 		pr_err("Initialization failed\n");
 		goto out_free_dmar;
 	}
-	up_write(&dmar_global_lock);
 
 	init_iommu_pm_ops();
 
-	down_read(&dmar_global_lock);
 	for_each_active_iommu(iommu, drhd) {
 		/*
 		 * The flush queue implementation does not perform
@@ -4127,13 +4108,11 @@ int __init intel_iommu_init(void)
 				       "%s", iommu->name);
 		iommu_device_register(&iommu->iommu, &intel_iommu_ops, NULL);
 	}
-	up_read(&dmar_global_lock);
 
 	bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
 	if (si_domain && !hw_pass_through)
 		register_memory_notifier(&intel_iommu_memory_nb);
 
-	down_read(&dmar_global_lock);
 	if (probe_acpi_namespace_devices())
 		pr_warn("ACPI name space devices didn't probe correctly\n");
 
@@ -4144,17 +4123,15 @@ int __init intel_iommu_init(void)
 
 		iommu_disable_protect_mem_regions(iommu);
 	}
-	up_read(&dmar_global_lock);
-
-	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
 
 	intel_iommu_enabled = 1;
+	dmar_register_bus_notifier();
+	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
 
 	return 0;
 
 out_free_dmar:
 	intel_iommu_free_dmars();
-	up_write(&dmar_global_lock);
 	return ret;
 }
 
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index cbd714a198a0a..f3a3d95df5325 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -69,6 +69,7 @@ struct dmar_pci_notify_info {
 
 extern struct rw_semaphore dmar_global_lock;
 extern struct list_head dmar_drhd_units;
+extern int intel_iommu_enabled;
 
 #define for_each_drhd_unit(drhd)					\
 	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list,		\
@@ -92,7 +93,8 @@ extern struct list_head dmar_drhd_units;
 static inline bool dmar_rcu_check(void)
 {
 	return rwsem_is_locked(&dmar_global_lock) ||
-	       system_state == SYSTEM_BOOTING;
+	       system_state == SYSTEM_BOOTING ||
+	       (IS_ENABLED(CONFIG_INTEL_IOMMU) && !intel_iommu_enabled);
 }
 
 #define	dmar_rcu_dereference(p)	rcu_dereference_check((p), dmar_rcu_check())