build-sys: Add rust feature option

Add rust feature in meson.build, configure, to prepare for adding Rust
code in the followup commits.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Link: https://lore.kernel.org/r/14642d80fbccbc60f7aa78b449a7deb5e2784ed9.1727961605.git.manos.pitsidianakis@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Kconfig

@@ -4,3 +4,4 @@ source accel/Kconfig
 source target/Kconfig
 source hw/Kconfig
 source semihosting/Kconfig
+source rust/Kconfig

Kconfig.host

@@ -52,3 +52,6 @@ config VFIO_USER_SERVER_ALLOWED
 
 config HV_BALLOON_POSSIBLE
     bool
+
+config HAVE_RUST
+    bool

MAINTAINERS

@@ -4188,6 +4188,11 @@ F: docs/sphinx/
 F: docs/_templates/
 F: docs/devel/docs.rst
 
+Rust build system integration
+M: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+S: Maintained
+F: rust/Kconfig
+
 Miscellaneous
 -------------
 Performance Tools and Tests

meson.build

@@ -70,6 +70,19 @@ if host_os == 'darwin' and \
   all_languages += ['objc']
   objc = meson.get_compiler('objc')
 endif
+have_rust = false
+if not get_option('rust').disabled() and add_languages('rust', required: get_option('rust'), native: false)
+  rustc = meson.get_compiler('rust')
+  have_rust = true
+  if rustc.version().version_compare('<1.80.0')
+    if get_option('rust').enabled()
+      error('rustc version ' + rustc.version() + ' is unsupported: Please upgrade to at least 1.80.0')
+    else
+      warning('rustc version ' + rustc.version() + ' is unsupported: Disabling Rust compilation. Please upgrade to at least 1.80.0 to use Rust.')
+      have_rust = false
+    endif
+  endif
+endif
 
 dtrace = not_found
 stap = not_found
@@ -2158,6 +2171,7 @@ endif
 
 config_host_data = configuration_data()
 
+config_host_data.set('CONFIG_HAVE_RUST', have_rust)
 audio_drivers_selected = []
 if have_system
   audio_drivers_available = {
@@ -3097,7 +3111,8 @@ host_kconfig = \
   (host_os == 'linux' ? ['CONFIG_LINUX=y'] : []) + \
   (multiprocess_allowed ? ['CONFIG_MULTIPROCESS_ALLOWED=y'] : []) + \
   (vfio_user_server_allowed ? ['CONFIG_VFIO_USER_SERVER_ALLOWED=y'] : []) + \
-  (hv_balloon ? ['CONFIG_HV_BALLOON_POSSIBLE=y'] : [])
+  (hv_balloon ? ['CONFIG_HV_BALLOON_POSSIBLE=y'] : []) + \
+  (have_rust ? ['CONFIG_HAVE_RUST=y'] : [])
 
 ignored = [ 'TARGET_XML_FILES', 'TARGET_ABI_DIR', 'TARGET_ARCH' ]
 
@@ -4308,6 +4323,11 @@ if 'objc' in all_languages
 else
   summary_info += {'Objective-C compiler': false}
 endif
+summary_info += {'Rust support':      have_rust}
+if have_rust
+  summary_info += {'rustc version':      rustc.version()}
+  summary_info += {'rustc':      ' '.join(rustc.cmd_array())}
+endif
 option_cflags = (get_option('debug') ? ['-g'] : [])
 if get_option('optimization') != 'plain'
   option_cflags += ['-O' + get_option('optimization')]

meson_options.txt

@@ -373,3 +373,6 @@ option('hexagon_idef_parser', type : 'boolean', value : true,
 
 option('x86_version', type : 'combo', choices : ['0', '1', '2', '3', '4'], value: '1',
        description: 'tweak required x86_64 architecture version beyond compiler default')
+
+option('rust', type: 'feature', value: 'auto',
+       description: 'Rust support')

scripts/meson-buildoptions.sh

@@ -172,6 +172,7 @@ meson_options_help() {
   printf "%s\n" '  rbd             Ceph block device driver'
   printf "%s\n" '  rdma            Enable RDMA-based migration'
   printf "%s\n" '  replication     replication support'
+  printf "%s\n" '  rust            Rust support'
   printf "%s\n" '  rutabaga-gfx    rutabaga_gfx support'
   printf "%s\n" '  sdl             SDL user interface'
   printf "%s\n" '  sdl-image       SDL Image support for icons'
@@ -456,6 +457,8 @@ _meson_option_parse() {
     --disable-replication) printf "%s" -Dreplication=disabled ;;
     --enable-rng-none) printf "%s" -Drng_none=true ;;
     --disable-rng-none) printf "%s" -Drng_none=false ;;
+    --enable-rust) printf "%s" -Drust=enabled ;;
+    --disable-rust) printf "%s" -Drust=disabled ;;
     --enable-rutabaga-gfx) printf "%s" -Drutabaga_gfx=enabled ;;
     --disable-rutabaga-gfx) printf "%s" -Drutabaga_gfx=disabled ;;
     --enable-safe-stack) printf "%s" -Dsafe_stack=true ;;