diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index df96a0f..37d73024 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -408,28 +408,14 @@
 	return num;
 }
 
-/* Notify firmware how many CPUs are idle */
-static void acpi_pad_ost(acpi_handle handle, int stat,
-	uint32_t idle_cpus)
-{
-	union acpi_object params[3] = {
-		{.type = ACPI_TYPE_INTEGER,},
-		{.type = ACPI_TYPE_INTEGER,},
-		{.type = ACPI_TYPE_BUFFER,},
-	};
-	struct acpi_object_list arg_list = {3, params};
-
-	params[0].integer.value = ACPI_PROCESSOR_AGGREGATOR_NOTIFY;
-	params[1].integer.value =  stat;
-	params[2].buffer.length = 4;
-	params[2].buffer.pointer = (void *)&idle_cpus;
-	acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
-}
-
 static void acpi_pad_handle_notify(acpi_handle handle)
 {
 	int num_cpus;
 	uint32_t idle_cpus;
+	struct acpi_buffer param = {
+		.length = 4,
+		.pointer = (void *)&idle_cpus,
+	};
 
 	mutex_lock(&isolated_cpus_lock);
 	num_cpus = acpi_pad_pur(handle);
@@ -439,7 +425,7 @@
 	}
 	acpi_pad_idle_cpus(num_cpus);
 	idle_cpus = acpi_pad_idle_cpus_num();
-	acpi_pad_ost(handle, 0, idle_cpus);
+	acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
 	mutex_unlock(&isolated_cpus_lock);
 }
 
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index afe6f9a..e7e5844 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -311,9 +311,7 @@
 	capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_PPC_OST_SUPPORT;
 #endif
 
-#ifdef ACPI_HOTPLUG_OST
 	capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_HOTPLUG_OST_SUPPORT;
-#endif
 
 	if (!ghes_disable)
 		capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_APEI_SUPPORT;
@@ -410,7 +408,7 @@
 	return;
 
  err:
-	acpi_evaluate_hotplug_ost(handle, type, ost_code, NULL);
+	acpi_evaluate_ost(handle, type, ost_code, NULL);
 }
 
 /* --------------------------------------------------------------------------
diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index ff90054..cfc8aba 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -156,17 +156,9 @@
  */
 static void acpi_processor_ppc_ost(acpi_handle handle, int status)
 {
-	union acpi_object params[2] = {
-		{.type = ACPI_TYPE_INTEGER,},
-		{.type = ACPI_TYPE_INTEGER,},
-	};
-	struct acpi_object_list arg_list = {2, params};
-
-	if (acpi_has_method(handle, "_OST")) {
-		params[0].integer.value = ACPI_PROCESSOR_NOTIFY_PERFORMANCE;
-		params[1].integer.value =  status;
-		acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
-	}
+	if (acpi_has_method(handle, "_OST"))
+		acpi_evaluate_ost(handle, ACPI_PROCESSOR_NOTIFY_PERFORMANCE,
+				  status, NULL);
 }
 
 int acpi_processor_ppc_has_changed(struct acpi_processor *pr, int event_flag)
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index eb7a1ff..1870223 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -474,8 +474,8 @@
 			dev_info(&adev->dev, "Eject disabled\n");
 			return -EPERM;
 		}
-		acpi_evaluate_hotplug_ost(adev->handle, ACPI_NOTIFY_EJECT_REQUEST,
-					  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
+		acpi_evaluate_ost(adev->handle, ACPI_NOTIFY_EJECT_REQUEST,
+				  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
 		return acpi_scan_hot_remove(adev);
 	}
 	return -EINVAL;
@@ -524,7 +524,7 @@
 		ost_code = ACPI_OST_SC_SUCCESS;
 
  err_out:
-	acpi_evaluate_hotplug_ost(adev->handle, src, ost_code, NULL);
+	acpi_evaluate_ost(adev->handle, src, ost_code, NULL);
 
  out:
 	acpi_bus_put_acpi_device(adev);
@@ -583,8 +583,8 @@
 		return count;
 
 	put_device(&acpi_device->dev);
-	acpi_evaluate_hotplug_ost(acpi_device->handle, ACPI_OST_EC_OSPM_EJECT,
-				  ACPI_OST_SC_NON_SPECIFIC_FAILURE, NULL);
+	acpi_evaluate_ost(acpi_device->handle, ACPI_OST_EC_OSPM_EJECT,
+			  ACPI_OST_SC_NON_SPECIFIC_FAILURE, NULL);
 	return status == AE_NO_MEMORY ? -ENOMEM : -EAGAIN;
 }
 
@@ -1757,6 +1757,20 @@
 	return false;
 }
 
+static bool acpi_object_is_system_bus(acpi_handle handle)
+{
+	acpi_handle tmp;
+
+	if (ACPI_SUCCESS(acpi_get_handle(NULL, "\\_SB", &tmp)) &&
+	    tmp == handle)
+		return true;
+	if (ACPI_SUCCESS(acpi_get_handle(NULL, "\\_TZ", &tmp)) &&
+	    tmp == handle)
+		return true;
+
+	return false;
+}
+
 static void acpi_set_pnp_ids(acpi_handle handle, struct acpi_device_pnp *pnp,
 				int device_type)
 {
@@ -1808,8 +1822,10 @@
 			acpi_add_id(pnp, ACPI_DOCK_HID);
 		else if (acpi_ibm_smbus_match(handle))
 			acpi_add_id(pnp, ACPI_SMBUS_IBM_HID);
-		else if (list_empty(&pnp->ids) && handle == ACPI_ROOT_OBJECT) {
-			acpi_add_id(pnp, ACPI_BUS_HID); /* \_SB, LNXSYBUS */
+		else if (list_empty(&pnp->ids) &&
+			 acpi_object_is_system_bus(handle)) {
+			/* \_SB, \_TZ, LNXSYBUS */
+			acpi_add_id(pnp, ACPI_BUS_HID);
 			strcpy(pnp->device_name, ACPI_BUS_DEVICE_NAME);
 			strcpy(pnp->device_class, ACPI_BUS_CLASS);
 		}
diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 85e3b61..0f5f78f 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -422,7 +422,7 @@
 EXPORT_SYMBOL(acpi_get_physical_device_location);
 
 /**
- * acpi_evaluate_hotplug_ost: Evaluate _OST for hotplug operations
+ * acpi_evaluate_ost: Evaluate _OST for hotplug operations
  * @handle: ACPI device handle
  * @source_event: source event code
  * @status_code: status code
@@ -433,17 +433,15 @@
  * When the platform does not support _OST, this function has no effect.
  */
 acpi_status
-acpi_evaluate_hotplug_ost(acpi_handle handle, u32 source_event,
-		u32 status_code, struct acpi_buffer *status_buf)
+acpi_evaluate_ost(acpi_handle handle, u32 source_event, u32 status_code,
+		  struct acpi_buffer *status_buf)
 {
-#ifdef ACPI_HOTPLUG_OST
 	union acpi_object params[3] = {
 		{.type = ACPI_TYPE_INTEGER,},
 		{.type = ACPI_TYPE_INTEGER,},
 		{.type = ACPI_TYPE_BUFFER,}
 	};
 	struct acpi_object_list arg_list = {3, params};
-	acpi_status status;
 
 	params[0].integer.value = source_event;
 	params[1].integer.value = status_code;
@@ -455,13 +453,9 @@
 		params[2].buffer.length = 0;
 	}
 
-	status = acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
-	return status;
-#else
-	return AE_OK;
-#endif
+	return acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
 }
-EXPORT_SYMBOL(acpi_evaluate_hotplug_ost);
+EXPORT_SYMBOL(acpi_evaluate_ost);
 
 /**
  * acpi_handle_printk: Print message with ACPI prefix and object path
diff --git a/drivers/xen/xen-acpi-cpuhotplug.c b/drivers/xen/xen-acpi-cpuhotplug.c
index 80875fb..3e62ee4 100644
--- a/drivers/xen/xen-acpi-cpuhotplug.c
+++ b/drivers/xen/xen-acpi-cpuhotplug.c
@@ -313,7 +313,7 @@
 		goto out;
 	}
 
-	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
+	(void) acpi_evaluate_ost(handle, event, ost_code, NULL);
 
 out:
 	acpi_scan_lock_release();
diff --git a/drivers/xen/xen-acpi-memhotplug.c b/drivers/xen/xen-acpi-memhotplug.c
index f8d1862..34e40b7 100644
--- a/drivers/xen/xen-acpi-memhotplug.c
+++ b/drivers/xen/xen-acpi-memhotplug.c
@@ -285,7 +285,7 @@
 		return;
 	}
 
-	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
+	(void) acpi_evaluate_ost(handle, event, ost_code, NULL);
 	return;
 }
 
diff --git a/drivers/xen/xen-acpi-pad.c b/drivers/xen/xen-acpi-pad.c
index 40c4bc06..f83b754 100644
--- a/drivers/xen/xen-acpi-pad.c
+++ b/drivers/xen/xen-acpi-pad.c
@@ -77,27 +77,14 @@
 	return num;
 }
 
-/* Notify firmware how many CPUs are idle */
-static void acpi_pad_ost(acpi_handle handle, int stat,
-	uint32_t idle_nums)
-{
-	union acpi_object params[3] = {
-		{.type = ACPI_TYPE_INTEGER,},
-		{.type = ACPI_TYPE_INTEGER,},
-		{.type = ACPI_TYPE_BUFFER,},
-	};
-	struct acpi_object_list arg_list = {3, params};
-
-	params[0].integer.value = ACPI_PROCESSOR_AGGREGATOR_NOTIFY;
-	params[1].integer.value =  stat;
-	params[2].buffer.length = 4;
-	params[2].buffer.pointer = (void *)&idle_nums;
-	acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
-}
-
 static void acpi_pad_handle_notify(acpi_handle handle)
 {
 	int idle_nums;
+	struct acpi_buffer param = {
+		.length = 4,
+		.pointer = (void *)&idle_nums,
+	};
+
 
 	mutex_lock(&xen_cpu_lock);
 	idle_nums = acpi_pad_pur(handle);
@@ -109,7 +96,8 @@
 	idle_nums = xen_acpi_pad_idle_cpus(idle_nums)
 		    ?: xen_acpi_pad_idle_cpus_num();
 	if (idle_nums >= 0)
-		acpi_pad_ost(handle, 0, idle_nums);
+		acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY,
+				  0, &param);
 	mutex_unlock(&xen_cpu_lock);
 }
 
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 660f505..ca4ac46 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -49,8 +49,8 @@
 			struct acpi_object_list *arguments,
 			struct acpi_handle_list *list);
 acpi_status
-acpi_evaluate_hotplug_ost(acpi_handle handle, u32 source_event,
-			u32 status_code, struct acpi_buffer *status_buf);
+acpi_evaluate_ost(acpi_handle handle, u32 source_event, u32 status_code,
+		  struct acpi_buffer *status_buf);
 
 acpi_status
 acpi_get_physical_device_location(acpi_handle handle, struct acpi_pld_info **pld);