Allow reusing defaults in per-node kernel_append_params

It may be convenient to use [pxe/redfish/...]kernel_append_params as
the universal defaults, while using {driver,instance}_info to only
append values. This change allows that by replacing %default% with
the value of the applicable configuration option.

An example use case: CoreOS requires an additional artifact (root
filesystem URL) when PXE booting.

While here, fix the PXE/iPXE interface documentation.

Change-Id: I829291ab5cc19ec2ca43bc45815d012697f0b408

10 files changed, 121 insertions, 41 deletions

diff --git a/doc/source/admin/drivers/redfish.rst b/doc/source/admin/drivers/redfish.rst
index d2d93d9ff..dcae7edd0 100644
--- a/doc/source/admin/drivers/redfish.rst
+++ b/doc/source/admin/drivers/redfish.rst
@@ -206,8 +206,17 @@ user-specified kernel command line parameters.
 .. note::
    The ``driver_info`` field is supported starting with the Xena release.
 
+Starting with the Zed cycle, you can combine the parameters from the
+configuration and from the node using the special ``%default%`` syntax:
+
+.. code-block:: bash
+
+  baremetal node set node-0 \
+    --driver-info kernel_append_params="%default% console=ttyS0,115200n8"
+
 For ramdisk boot, the ``instance_info[ramdisk_kernel_arguments]`` property
-serves the same purpose.
+serves the same purpose (``%default%`` is not supported since there is no
+default value in the configuration).
 
 Pre-built ISO images
 ~~~~~~~~~~~~~~~~~~~~
diff --git a/doc/source/admin/interfaces/boot.rst b/doc/source/admin/interfaces/boot.rst
index 5cee944c6..cd9420cc9 100644
--- a/doc/source/admin/interfaces/boot.rst
+++ b/doc/source/admin/interfaces/boot.rst
@@ -16,15 +16,15 @@ Check your driver documentation at :doc:`../drivers` for details.
 PXE boot
 --------
 
-The ``pxe`` boot interface uses PXE_ or iPXE_ to deliver the target
-kernel/ramdisk pair. PXE uses relatively slow and unreliable TFTP protocol
-for transfer, while iPXE uses HTTP. The downside of iPXE is that it's less
-common, and usually requires bootstrapping using PXE first.
-
-The ``pxe`` boot interface works by preparing a PXE/iPXE environment for a
-node on the file system, then instructing the DHCP provider (for example,
-the Networking service) to boot the node from it. See
-ref:`direct-deploy-example` for a better understanding of the whole deployment
+The ``pxe`` and ``ipxe`` boot interfaces uses PXE_ or iPXE_ accordingly to
+deliver the target kernel/ramdisk pair. PXE uses relatively slow and unreliable
+TFTP protocol for transfer, while iPXE uses HTTP. The downside of iPXE is that
+it's less common, and usually requires bootstrapping using PXE first.
+
+The ``pxe`` and ``ipxe`` boot interfaces work by preparing a PXE/iPXE
+environment for a node on the file system, then instructing the DHCP provider
+(for example, the Networking service) to boot the node from it. See
+:ref:`direct-deploy-example` for a better understanding of the whole deployment
 process.
 
 .. note::
@@ -32,13 +32,50 @@ process.
     instead of conventional BIOS boot. This is particularly important for CPU
     architectures that do not have BIOS support at all.
 
-The ``pxe`` boot interface is used by default for many hardware types,
-including ``ipmi``. Some hardware types, notably ``ilo`` and ``irmc`` have their
-specific implementations of the PXE boot interface.
+The ``ipxe`` boot interface is used by default for many hardware types,
+including ``ipmi``. Some hardware types, notably ``ilo`` and ``irmc`` have
+their specific implementations of the PXE boot interface.
 
 Additional configuration is required for this boot interface - see
 :doc:`/install/configure-pxe` for details.
 
+Kernel parameters
+~~~~~~~~~~~~~~~~~
+
+If you need to pass additional kernel parameters to the deployment/cleaning
+ramdisk (for example, to configure serial console), use the following
+configuration option:
+
+.. code-block:: ini
+
+    [pxe]
+    kernel_append_params = nofb nomodeset vga=normal
+
+.. note::
+   The option was called ``pxe_append_params`` before the Xena cycle.
+
+Per-node and per-instance overrides are also possible, for example:
+
+.. code-block:: bash
+
+  baremetal node set node-0 \
+    --driver-info kernel_append_params="nofb nomodeset vga=normal"
+  baremetal node set node-0 \
+    --instance-info kernel_append_params="nofb nomodeset vga=normal"
+
+Starting with the Zed cycle, you can combine the parameters from the
+configuration and from the node using the special ``%default%`` syntax:
+
+.. code-block:: bash
+
+  baremetal node set node-0 \
+    --driver-info kernel_append_params="%default% console=ttyS0,115200n8"
+
+Together with the configuration above, the following parameters will be
+appended to the kernel command line::
+
+    nofb nomodeset vga=normal console=ttyS0,115200n8
+
 Common options
 --------------
 
diff --git a/ironic/drivers/modules/ilo/boot.py b/ironic/drivers/modules/ilo/boot.py
index 5087e3998..7f5c5adcf 100644
--- a/ironic/drivers/modules/ilo/boot.py
+++ b/ironic/drivers/modules/ilo/boot.py
@@ -74,12 +74,8 @@ OPTIONAL_PROPERTIES = {
     'ilo_add_certificates': _("Boolean value that indicates whether the "
                               "certificates require to be added to the "
                               "iLO."),
-    'kernel_append_params': _("Additional kernel parameters to pass down "
-                              "to instance kernel. These parameters can "
-                              "be consumed by the kernel or by the "
-                              "applications by reading /proc/cmdline. "
-                              "Mind severe cmdline size limit. Overrides "
-                              "[ilo]/kernel_append_params ironic option.")
+    'kernel_append_params': driver_utils.KERNEL_APPEND_PARAMS_DESCRIPTION %
+    {'option_group': 'ilo'},
 }
 COMMON_PROPERTIES = REQUIRED_PROPERTIES
 
diff --git a/ironic/drivers/modules/irmc/boot.py b/ironic/drivers/modules/irmc/boot.py
index 1195a0670..84964bd2f 100644
--- a/ironic/drivers/modules/irmc/boot.py
+++ b/ironic/drivers/modules/irmc/boot.py
@@ -80,13 +80,8 @@ OPTIONAL_PROPERTIES = {
           "the IPv4 subnet mask that the storage network is configured to "
           "utilize, in a range between 1 and 31 inclusive. This is necessary "
           "for booting a node from a remote iSCSI volume. Optional."),
-    'kernel_append_params': _("Additional kernel parameters to pass down to "
-                              "instance kernel. These parameters can be "
-                              "consumed by the kernel or by the applications "
-                              "by reading /proc/cmdline. Mind severe cmdline "
-                              "size limit. Overrides "
-                              "[irmc]/kernel_append_params ironic "
-                              "option."),
+    'kernel_append_params': driver_utils.KERNEL_APPEND_PARAMS_DESCRIPTION %
+    {'option_group': 'irmc'},
 }
 
 COMMON_PROPERTIES = REQUIRED_PROPERTIES.copy()
diff --git a/ironic/drivers/modules/pxe_base.py b/ironic/drivers/modules/pxe_base.py
index a89c9e443..317b65b85 100644
--- a/ironic/drivers/modules/pxe_base.py
+++ b/ironic/drivers/modules/pxe_base.py
@@ -50,13 +50,8 @@ RESCUE_PROPERTIES = {
                         'required for rescue mode.'),
 }
 OPTIONAL_PROPERTIES = {
-    'kernel_append_params': _("Additional kernel parameters to pass down to "
-                              "instance kernel. These parameters can be "
-                              "consumed by the kernel or by the applications "
-                              "by reading /proc/cmdline. Mind severe cmdline "
-                              "size limit. Overrides "
-                              "[pxe]/kernel_append_params ironic "
-                              "option."),
+    'kernel_append_params': driver_utils.KERNEL_APPEND_PARAMS_DESCRIPTION %
+    {'option_group': 'pxe'},
 }
 COMMON_PROPERTIES = REQUIRED_PROPERTIES.copy()
 COMMON_PROPERTIES.update(driver_utils.OPTIONAL_PROPERTIES)
diff --git a/ironic/drivers/modules/redfish/boot.py b/ironic/drivers/modules/redfish/boot.py
index 55c826fc6..1ce05ced9 100644
--- a/ironic/drivers/modules/redfish/boot.py
+++ b/ironic/drivers/modules/redfish/boot.py
@@ -46,13 +46,8 @@ OPTIONAL_PROPERTIES = {
                               "driver should use virtual media USB or floppy "
                               "device for passing configuration information "
                               "to the ramdisk. Defaults to False. Optional."),
-    'kernel_append_params': _("Additional kernel parameters to pass down to "
-                              "instance kernel. These parameters can be "
-                              "consumed by the kernel or by the applications "
-                              "by reading /proc/cmdline. Mind severe cmdline "
-                              "size limit. Overrides "
-                              "[redfish]/kernel_append_params ironic "
-                              "option."),
+    'kernel_append_params': driver_utils.KERNEL_APPEND_PARAMS_DESCRIPTION %
+    {'option_group': 'redfish'},
     'bootloader': _("URL or Glance UUID  of the EFI system partition "
                     "image containing EFI boot loader. This image will be "
                     "used by ironic when building UEFI-bootable ISO "
diff --git a/ironic/drivers/utils.py b/ironic/drivers/utils.py
index 5e1596eb4..fc5cdcf0d 100644
--- a/ironic/drivers/utils.py
+++ b/ironic/drivers/utils.py
@@ -384,6 +384,17 @@ OPTIONAL_PROPERTIES = {
 }
 
 
+KERNEL_APPEND_PARAMS_DESCRIPTION = _(
+    "Additional kernel parameters to pass down to instance kernel. "
+    "These parameters can be consumed by the kernel or by the applications "
+    "by reading /proc/cmdline. Mind severe cmdline size limit. "
+    "When used with virtual media, only applies to ISO images that Ironic "
+    "builds, but not to pre-built ISOs provided via e.g. deploy_iso. "
+    "Overrides the [%(option_group)s]/kernel_append_params configuration "
+    "option, use %%default%% to insert its value."
+)
+
+
 def get_kernel_append_params(node, default):
     """Get the applicable kernel params.
 
@@ -399,7 +410,7 @@ def get_kernel_append_params(node, default):
     for location in ('instance_info', 'driver_info'):
         result = getattr(node, location).get('kernel_append_params')
         if result is not None:
-            return result
+            return result.replace('%default%', default or '')
 
     return default
 
diff --git a/ironic/tests/unit/common/test_pxe_utils.py b/ironic/tests/unit/common/test_pxe_utils.py
index 5ba0033a7..77ac5f4d3 100644
--- a/ironic/tests/unit/common/test_pxe_utils.py
+++ b/ironic/tests/unit/common/test_pxe_utils.py
@@ -1712,6 +1712,15 @@ class PXEBuildConfigOptionsTestCase(db_base.DbTestCase):
         self._test_build_pxe_config_options_pxe(whle_dsk_img=True,
                                                 expected_pxe_params='params2')
 
+    def test_build_pxe_config_options_kernel_params_with_default(self):
+        info = self.node.driver_info
+        info['kernel_append_params'] = 'param1 %default% params2'
+        self.node.driver_info = info
+        self.node.save()
+        self._test_build_pxe_config_options_pxe(
+            whle_dsk_img=True,
+            expected_pxe_params='param1 test_param params2')
+
     def test_build_pxe_config_options_kernel_params_from_instance_info(self):
         info = self.node.instance_info
         info['kernel_append_params'] = 'params2'
diff --git a/ironic/tests/unit/drivers/modules/test_image_utils.py b/ironic/tests/unit/drivers/modules/test_image_utils.py
index 29db32c56..6d79629d9 100644
--- a/ironic/tests/unit/drivers/modules/test_image_utils.py
+++ b/ironic/tests/unit/drivers/modules/test_image_utils.py
@@ -582,6 +582,29 @@ class RedfishImageUtilsTestCase(db_base.DbTestCase):
     @mock.patch.object(image_utils.ImageHandler, 'publish_image',
                        autospec=True)
     @mock.patch.object(images, 'create_boot_iso', autospec=True)
+    def test__prepare_iso_image_kernel_params_defaults(
+            self, mock_create_boot_iso, mock_publish_image):
+        with task_manager.acquire(self.context, self.node.uuid,
+                                  shared=True) as task:
+            kernel_params = 'network-config=base64-cloudinit-blob'
+
+            task.node.driver_info['kernel_append_params'] = \
+                f'%default% {kernel_params}'
+
+            image_utils._prepare_iso_image(
+                task, 'http://kernel/img', 'http://ramdisk/img',
+                bootloader_href=None, root_uuid=task.node.uuid)
+
+            mock_create_boot_iso.assert_called_once_with(
+                mock.ANY, mock.ANY, 'http://kernel/img', 'http://ramdisk/img',
+                boot_mode='uefi', esp_image_href=None,
+                kernel_params=f'nofb nomodeset vga=normal {kernel_params}',
+                root_uuid='1be26c0b-03f2-4d2e-ae87-c02d7f33c123',
+                inject_files=None)
+
+    @mock.patch.object(image_utils.ImageHandler, 'publish_image',
+                       autospec=True)
+    @mock.patch.object(images, 'create_boot_iso', autospec=True)
     def test__prepare_iso_image_kernel_params_driver_info_bios(
             self, mock_create_boot_iso, mock_publish_image):
         self.config(default_boot_mode='bios', group='deploy')
diff --git a/releasenotes/notes/append-params-a8b9f844328da83e.yaml b/releasenotes/notes/append-params-a8b9f844328da83e.yaml
new file mode 100644
index 000000000..8a17a0f28
--- /dev/null
+++ b/releasenotes/notes/append-params-a8b9f844328da83e.yaml
@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    When using per-node kernel parameters, i.e. ``kernel_append_params`` in the
+    node's ``instance_info`` or ``driver_info``, it is now possible to insert
+    the value of the driver's configuration option (e.g.
+    ``[pxe]kernel_append_params`` via the special ``%default%`` syntax, e.g.::
+
+      baremetal node set node-0 \
+        --driver-info kernel_append_params="%default% foo=bar"