Re: [RFC PATCH v1 01/43] Add option to enable/disable helper-to-tcg

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/22/24 18:30, Richard Henderson wrote:
> On 11/20/24 19:49, Anton Johansson wrote:
>> Adds a meson option for enabling/disabling helper-to-tcg along with a
>> CONFIG_* definition.
>>
>> CONFIG_* will in future commits be used to conditionally include the
>> helper-to-tcg subproject, and to remove unneeded code/memory when
>> helper-to-tcg is not in use.
>>
>> Current meson option is limited to Hexagon, as helper-to-tcg will be
>> included as a subproject from target/hexagon.  This will change in the
>> future if multiple frontends adopt helper-to-tcg.
>>
>> Signed-off-by: Anton Johansson <anjo@rev.ng>
>> ---
>>   meson.build                   | 7 +++++++
>>   meson_options.txt             | 2 ++
>>   scripts/meson-buildoptions.sh | 5 +++++
>>   3 files changed, 14 insertions(+)
> 
> Looks ok.  Could probably stand another set of meson eyes.
> 
> Acked-by: Richard Henderson <richard.henderson@linaro.org>

/me bows

Since the subproject has a pretty hefty (and specific) set of
dependencies, please make this a "feature" option.  This allows
subprojects/helper-to-tcg to disable itself if it cannot find
a dependency or otherwise invokes error(), without breaking the
build.  The --enable-hexagon-helper-to-tcg flag however *will*
force the subproject to be buildable, just like all other
QEMU feature options.

Something like this:


########################
# Target configuration #
########################

# a bit gross to hardcode hexagon, but acceptable given the name of the option
helper_to_tcg = subproject('helper-to-tcg', get_option('hexagon_helper_to_tcg') \
    .disable_auto_if('hexagon-linux-user' not in target_dirs))


and replace helper_to_tcg_enabled throughout with helper_to_tcg.found().

>> +  if helper_to_tcg_enabled
>> +    config_target += {
>> +      'CONFIG_HELPER_TO_TCG': 'y',
>> +    }
>> +  endif

Here I would add instead add CONFIG_HELPER_TO_TCG (maybe renamed to
TARGET_HELPER_TO_TCG) in configs/targets/) and add before the loop:

ignored = [ 'TARGET_XML_FILES', 'TARGET_ABI_DIR', 'TARGET_ARCH' ]
if not helper_to_tcg.found()
   # do not define it if it is not usable
   ignored += ['TARGET_HELPER_TO_TCG']
endif

Paolo