Re: [PATCH v5 11/17] tests/docker: strip remaining caching logic from docker.py

[Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>]

On 9/18/2026 4:57 AM, Alex Bennée wrote:
> Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> writes:
> 
>> On 9/18/2026 12:30 AM, Alex Bennée wrote:
>>> Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> writes:
>>>
>>>> On 9/17/2026 3:18 PM, Richard Henderson wrote:
>>>>> On 9/17/26 12:00, Pierrick Bouvier wrote:
>>>>>> On 9/17/2026 2:49 PM, Alex Bennée wrote:
>>>>>>> how much time? it flies past when I run a rebuild.
>>>>>>>
>>>>>>
>>>>>> For a no-op tcg-tests build (i.e. with tests already built):
>>>>>>
>>>>>> - With current patch:
>>>>>> time ninja -C tcg-tests
>>>>>> ...
>>>>>> verbose pull and build
>>>>>> 320 lines of output
>>>>>> ...
>>>>>> real    0m15.817s
>>>>>> user    0m1.342s
>>>>>> sys     0m0.840s
>>>
>>>   ✗  time ninja
>>>   [1/114] Generating qemu-version.h with a custom command (wrapped by meson to capture output)
>>>
>>>   ________________________________________________________
>>>   Executed in  515.16 millis    fish           external
>>>      usr time  433.82 millis  968.00 micros  432.85 millis
>>>      sys time   86.05 millis  253.00 micros   85.80 millis
>>>
>>> Not sure whats going on there then. The whole tcg suite completes in
>>> under a minute (and would be shorter if i386-linux-user-test-i386-fprem
>>> and riscv64-softmmu-plugin-discons-with-interruptedmemory where in the
>>> thorough test suite).
>>>
>>
>> You need to run "ninja tcg-tests" explicitly, as tests (and images) are
>> not built by default.
> 
> What is that target trying to do? Because when I run:
>

tcg-tests will build only tests (and their dependencies, container images).

tcg/tests/meson.build
```
if exe_name not in built_tests
    exe = custom_target(exe_name,
                        input: file,
                        command: [cc, '@INPUT@',
                                  '-o', '@OUTPUT@', '-static',
                                  '-MMD', '-MF', '@DEPFILE@',
                                  '-Wall', '-Werror',
                                  '-O0', '-g', '-fno-strict-aliasing',
                                  cflags],
                        depfile: exe_name + '.d',
                        output: exe_name + '.test',
                        depends: exe_depends,
                        depend_files: build_test_depend_files,
                        build_by_default: false)
    exe_targets += exe
endif

...

if exe_targets.length() > 0
  # finally create a top level target to rebuild all tests
  alias_target('tcg-tests', exe_targets)
endif
```

build_test_depend_files contains container images, and eventually some
generated files given in "depends" field of test declaration. It's used
for x86 tests who need to generate headers.

Test compilation generates depfile (.d), which meson reintegrates
automatically, so test depends on all their headers correctly.

```
build_test_depends = []
build_test_depends_files = []
...
      build_test_depends += image_targets[cc_dockerfile]
      build_test_depend_files += dockerfile
...
exe_depends = build_test_depends
if 'depends' in setup
    exe_depends += setup['depends']
endif

exe..
   depends: exe_depends,
   depend_files: build_test_depend_files,
# meson has distinct fields for target dependencies and file
# dependencies, which is a bit confusing IMHO.
```

>   ./run meson test --suite tcg
>

This target will build test dependencies, and run them also.

```
test(test_name, env, args: cmd,
     depends: test_depends,
     timeout: 120,
     suite: ['tcg', 'tcg-' + target])
```

test_depends contains the test binary itself (as seen above), but also
qemu binaries, plugins.

```
test_depends = []
...
if 'plugin_test' in setup
   test_depends += plugin
endif
...
test_depends += qemu
```

Also, meson adds an implicit dependency on every target included in cmd
(args: cmd) array, which includes transitively test binaries and all
their deps.

> it still ends up rebuilding the test binaries. 
>

So from all code above, it should now be clear that:
   `meson --suite tcg`
will automatically build all that is needed (and no more - like no other
test binaries). Also, if you modify an existing dockerfile, it will
automatically rebuilds all tests associated for you.

Same goes for any subsuite: tcg-aarch64-softmmu, which only build
qemu-system-aarch64, needed container images, and only test binaries.

Beyond a better maintainability, one of the goal of original series was
to have *complete* dependencies, so we never need to add fake "all"
dependencies on Makefile level, which is why I insisted to remove the
patch that was doing it for images in this series.

Hope it's more clear now!

>>
>>>>>
>>>>> The variance from the middle of the pacific ocean, and associated
>>>>> network latency, is between 20 and 27 seconds.
>>>>>
>>>>> Amusingly, with the network actively disconnected (airplane mode), the
>>>>> no-op build completes in 1 to 2 seconds.
>>>>>
>>>>
>>>> Funny, on my side if hangs a long time (timeout 30s), then retry 3 times
>>>> per image. I tried it on WSL on my windows laptop.
>>>>
>>>>>
>>>>> r~
>>>
>