feat(build): look up VM configurations through a repository option

CONFIG_REPO joins CONFIG_SRC in Kconfig, empty meaning the in-tree
configs folder, and CONFIG_SRC accepts a configuration name resolved in
that repository, a configuration folder, or a config.c path. Seeding
records the name as given (plus the repository when explicit) instead of
a resolved absolute path, keeping .config files portable; the config pin
covers both values.

Signed-off-by: Jose Martins <josemartins90@gmail.com>

Author: josecm

Makefile

@@ -66,6 +66,7 @@ lib_dir=$(src_dir)/lib
 core_dir=$(src_dir)/core
 platforms_dir=$(src_dir)/platform
 configs_dir=$(cur_dir)/configs
+config_repo_arg:=$(filter command environment,$(origin CONFIG_REPO))
 CONFIG_REPO?=$(configs_dir)
 scripts_dir:=$(cur_dir)/scripts
 ci_dir:=$(cur_dir)/ci
@@ -193,15 +194,16 @@ seed_plat_defconfig=$(wildcard $(platform_dir)/defconfig)
 seed_config_defconfig=$(strip $(if $(filter-out $(CONFIG_REPO),$(config_dir)), \
 	$(wildcard $(config_dir)/defconfig)))
 seed_defconfigs=$(seed_plat_defconfig) $(seed_config_defconfig)
-seed_config_src_arg=$(if $(config_src),--config-src $(abspath $(config_src)))
+seed_config_src_arg=$(if $(CONFIG),--config-src $(CONFIG)) \
+	$(if $(config_repo_arg),--config-repo $(CONFIG_REPO))
 seed_defconfig_args=\
 	$(if $(seed_plat_defconfig),--platform-defconfig $(seed_plat_defconfig)) \
 	$(if $(seed_config_defconfig),--config-defconfig $(seed_config_defconfig)) \
 	$(seed_config_src_arg)
 
 $(kconfig_file):
 	$(if $(PLATFORM),,$(error No configuration in $(build_dir): pass \
-		PLATFORM= and CONFIG=, or run make \
+		PLATFORM= and CONFIG= for a classic build, or run make \
 		$(if $(default_o),,O=$(O) )<platform>_defconfig first))
 	@echo "Seeding config		$(patsubst $(cur_dir)/%,%, $@)"
 	@mkdir -p $(dir $@)
@@ -247,28 +249,57 @@ endif
 ifneq ($(strip $(build_targets) $(filter listconfig,$(targets))),)
 -include $(kconfig_auto_conf)
 
+# A missing or out-of-date auto.conf is about to be (re)generated, after
+# which make restarts: validation against its values only runs once it is
+# current, never against stale ones
+kconfig_auto_stale:=$(if $(wildcard $(kconfig_auto_conf)),$(shell \
+	test $(kconfig_file) -nt $(kconfig_auto_conf) && echo y),y)
+
 ifneq ($(O),)
-# In the O= workflow the .config owns the platform and the VM configuration.
-# PLATFORM= must then agree with it and CONFIG= overrides the configuration
-# source for this invocation only. The checks are skipped while auto.conf is
-# still being (re)generated; make restarts with the resolved values
+# In the O= workflow the .config owns the platform and the VM configuration
 PLATFORM:=$(CONFIG_PLATFORM)
-ifneq ($(wildcard $(kconfig_auto_conf)),)
+ifeq ($(kconfig_auto_stale),)
 ifneq ($(PLATFORM),)
 ifeq ($(wildcard $(platform_dir)),)
  $(error Target platform $(PLATFORM) is not supported)
 endif
 endif
 ifeq ($(config_src),)
-config_src:=$(CONFIG_CONFIG_SRC)
-config_dir:=$(patsubst %/,%,$(dir $(config_src)))
-ifeq ($(notdir $(config_src)),config.c)
+config_spec:=$(CONFIG_CONFIG_SRC)
+config_repo:=$(strip $(if $(config_repo_arg),$(CONFIG_REPO), \
+	$(if $(CONFIG_CONFIG_REPO),$(CONFIG_CONFIG_REPO),$(configs_dir))))
+ifneq ($(build_targets),)
+ifeq ($(config_spec),)
+$(error No VM configuration set in $(kconfig_file): set it via menuconfig)
+endif
+endif
+# The stored configuration is a name looked up in the repository, a
+# configuration folder, or a config.c path
+ifeq ($(findstring /,$(config_spec)),)
+config_src:=$(wildcard $(config_repo)/$(config_spec).c)
+ifeq ($(config_src),)
+config_dir:=$(config_repo)/$(config_spec)
+-include $(config_dir)/config.mk
+ifeq ($(config_src),)
+config_src:=$(wildcard $(config_dir)/config.c)
+endif
+else
+config_dir:=$(config_repo)
+endif
+else ifeq ($(filter %.c,$(config_spec)),)
+config_dir:=$(patsubst %/,%,$(config_spec))
 -include $(config_dir)/config.mk
+ifeq ($(config_src),)
+config_src:=$(wildcard $(config_dir)/config.c)
+endif
+else
+config_src:=$(config_spec)
+config_dir:=$(patsubst %/,%,$(dir $(config_spec)))
 endif
 endif
 ifneq ($(build_targets),)
-ifeq ($(config_src),)
-$(error No VM configuration: pass CONFIG= or set CONFIG_SRC in menuconfig)
+ifeq ($(wildcard $(config_src)),)
+$(error VM configuration $(if $(config_spec),$(config_spec),$(CONFIG)) not found)
 endif
 endif
 endif
@@ -584,11 +615,11 @@ endif
 # Configuration frontends operating on this build's .config
 
 .PHONY: menuconfig
-menuconfig: $(if $(O),$(if $(PLATFORM),$(kconfig_file)),$(kconfig_file))
+menuconfig: $(if $(O),,$(kconfig_file))
 	@$(kconfig_env) python3 $(kconfig_tool) menuconfig
 
 .PHONY: listconfig
-listconfig: $(kconfig_file)
+listconfig: $(if $(O),,$(kconfig_file))
 	@$(kconfig_env) python3 $(kconfig_tool) list $(seed_defconfig_args)
 
 # Seed the build's .config without building

scripts/kconfig.py

@@ -40,6 +40,15 @@ def check_pin(kconf):
                      'use another directory')
 
 
+def apply_config_src(kconf, src):
+    if not kconf.syms['CONFIG_SRC'].visibility and \
+            kconf.syms['CONFIG_SRC'].str_value != src:
+        sys.exit('kconfig: the VM configuration is pinned to '
+                 f"{kconf.syms['CONFIG_SRC'].str_value}; reseed with "
+                 'a <platform>_defconfig target to change it')
+    kconf.syms['CONFIG_SRC'].set_value(src)
+
+
 def write_build_pin(kconf, pin_platform, pin_config):
     path = os.environ.get('BAO_BUILD_PIN')
     if not (pin_platform or pin_config) or path == '/dev/null' or \
@@ -57,6 +66,9 @@ def write_build_pin(kconf, pin_platform, pin_config):
         if pin_config and src:
             f.write('\nconfig CONFIG_PINNED\n\tdefault y\n\n'
                     f'config CONFIG_SRC\n\tdefault "{src}"\n')
+            repo = kconf.syms['CONFIG_REPO'].str_value
+            if repo:
+                f.write(f'\nconfig CONFIG_REPO\n\tdefault "{repo}"\n')
 
 
 def check_platform(kconf, platform):
@@ -95,8 +107,9 @@ def write_auto_conf(kconf, path):
 def write_auto_conf_header(kconf, path):
     with open(path, 'w') as f:
         for sym in emitted_syms(kconf):
-            # CONFIG_SRC is a build input consumed by make, not by code
-            if sym.name == 'CONFIG_SRC':
+            # The configuration lookup is a build input consumed by make,
+            # not by code
+            if sym.name in ('CONFIG_SRC', 'CONFIG_REPO'):
                 continue
             if sym.orig_type in (kconfiglib.BOOL, kconfiglib.TRISTATE):
                 if sym.tri_value > 0:
@@ -237,6 +250,7 @@ def main():
     parser.add_argument('--platform-defconfig')
     parser.add_argument('--config-defconfig')
     parser.add_argument('--config-src')
+    parser.add_argument('--config-repo')
     parser.add_argument('--pin-platform', action='store_true')
     parser.add_argument('--pin-config', action='store_true')
     parser.add_argument('--auto-conf')
@@ -261,12 +275,9 @@ def main():
         load_defconfigs(kconf, defconfigs)
         platform_symbol(kconf, platform).set_value(2)
         if args.config_src:
-            if not kconf.syms['CONFIG_SRC'].visibility and \
-                    kconf.syms['CONFIG_SRC'].str_value != args.config_src:
-                sys.exit('kconfig: the VM configuration is pinned to '
-                         f"{kconf.syms['CONFIG_SRC'].str_value}; reseed with "
-                         'a <platform>_defconfig target to change it')
-            kconf.syms['CONFIG_SRC'].set_value(args.config_src)
+            apply_config_src(kconf, args.config_src)
+        if args.config_repo:
+            kconf.syms['CONFIG_REPO'].set_value(args.config_repo)
         check_warnings(kconf)
         check_platform(kconf, platform)
         check_pin(kconf)

src/Kconfig

@@ -4,12 +4,20 @@
 mainmenu "Bao Hypervisor Configuration"
 
 config CONFIG_SRC
-	string "VM configuration (config.c path)" if !CONFIG_PINNED
+	string "VM configuration" if !CONFIG_PINNED
 	help
-	  Fully resolved path of the VM configuration source this build
-	  compiles. Filled in when the configuration is seeded with CONFIG=
-	  on the make command line; passing CONFIG= to a later build
-	  overrides it for that invocation without changing it here.
+	  The VM configuration this build compiles: a configuration name
+	  looked up in the configuration repository, a path to a
+	  configuration folder, or a path to a config.c file. Filled in
+	  when the configuration is seeded with CONFIG= on the make command
+	  line; passing CONFIG= to a later build overrides it for that
+	  invocation without changing it here.
+
+config CONFIG_REPO
+	string "Configuration repository" if !CONFIG_PINNED
+	help
+	  Directory where VM configuration names are looked up. Empty
+	  means the in-tree configs/ folder.
 
 comment "VM configuration: @CONFIG_SRC@ (pinned)"
 	depends on CONFIG_PINNED