doc: update compile-time configuration HLD

Starting from v2.4, ACRN configuration uses solely XML files to store
configuration data and customized scripts to manipulate
configurations. This patch updates the HLD of compile-time configuration to
reflect this properly.

As the refinement to the configuration toolset itself is still ongoing,
this patch only adds brief introduction to the key generated files involved
in ACRN configuration. More details will be added after the refinement
completes.

Tracked-On: #5644
Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Signed-off-by: Benjamin Fitch <benjamin.fitch@intel.com>

doc/developer-guides/hld/hv-config.rst

@@ -3,54 +3,44 @@
 Compile-Time Configuration
 ##########################
 
-.. note:: With ACRN release 2.4, ACRN configuration has changed
-   significantly and no longer uses Kconfig. The following information is
-   obsolete and will be updated to reflect the new ACRN configuration
-   architecture and tools.
-   Refer to :ref:`scenario-config-options` for a complete list of configuration symbols.
+As described in :ref:`acrn_configuration_tool`, ACRN hypervisor configurations
+are saved as XML files and used for compilation. At compile-time, configuration
+data in the board and scenario XMLs are converted to C header and source files
+that define macros, variables, and data structures to which the hypervisor can
+refer. This conversion has two main steps:
 
-The hypervisor provides a kconfig-like way for manipulating compile-time
-configurations. Basically the hypervisor defines a set of configuration
-symbols and declare their default value. A configuration file is
-created, containing the values of each symbol, before building the
-sources.
+1. **Static allocation of resources**, which statically reserves resources for
+   the VMs if only high-level requirements are given in the scenario
+   configurations. Examples include the runtime base address of the hypervisor
+   image and PCI BDF addresses of ivshmem virtual devices.
 
-Similar to Linux kconfig, there are three files involved:
+#. **Generation of C files**, which places the configuration data in the data
+   types and structures defined by the hypervisor.
 
--  **.config** This files stores the values of all configuration
-   symbols.
+Some key files, which can be found under the build directory of the hypervisor,
+are as follows.
 
--  **config.mk** This file is a conversion of .config in Makefile
-   syntax, and can be included in makefiles so that the build
-   process can rely on the configurations.
+- **.board.xml** and **.scenario.xml** These files contain the configuration
+  data used by that build.
 
--  **config.h** This file is a conversion of .config in C syntax, and is
-   automatically included in every source file so that the values of
-   the configuration symbols are available in the sources.
+- **configs/allocation.xml** contains the results of the static allocation.
 
-.. figure:: images/config-image103.png
-   :align: center
-   :name: config-build-workflow
+- **configs/config.mk** This file is a conversion of the hypervisor feature
+  configurations (specified in the scenario XML) in Makefile syntax, and can be
+  included in makefiles so that the build process can rely on the
+  configurations.
 
-   Hypervisor configuration and build workflow
+- **include/config.h** This file is a conversion of the hypervisor feature
+  configurations in C header syntax, and is automatically included in every
+  source file so that the values of the configuration symbols are available in
+  the sources.
 
-:numref:`config-build-workflow` shows the workflow of building the
-hypervisor:
+- **configs/boards** and **configs/scenarios** contain all the other generated C
+  headers and sources that encode the configuration data in the XML files.
 
-1. Three targets are introduced for manipulating the configurations.
-
-   a. **defconfig** creates a .config based on a predefined
-      configuration file.
-
-   b. **oldconfig** updates an existing .config after creating one if it
-      does not exist.
-
-   c. **menuconfig** presents a terminal UI to navigate and modify the
-      configurations in an interactive manner.
-
-2. The target oldconfig is also used to create a .config if a .config
-   file does not exist when building the source directly.
-
-3. The other two files for makefiles and C sources are regenerated after
-   .config changes.
+Whenever ``.board.xml`` or ``.scenario.xml`` is modified, the hypervisor will be
+rebuilt upon the next invocation of ``make``.
 
+For the concept and usage of the configuration toolset, refer to
+:ref:`acrn_configuration_tool`. For a complete list of configuration symbols,
+refer to :ref:`scenario-config-options`.