When running functional tests directly there are some heuristics
to figure out where the build directory lives, along with the
possibility to override the logic by setting the QEMU_BUILD_DIR
env variable. This env var is set as part of the test env when
run via Meson but not when run directly.

A particular flaw with the currently logic is that it silently
uses the wrong location when the build directory is a sub-dir
under "./build", which is a common usage scenario for some devs.

With the recent introduction of the 'run' script, we now have
the MESON_BUILD_ROOT env variable set unconditionally, so we
can rely on that from the functional tests to get the correct
location in all scenarios.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 tests/functional/meson.build         | 2 +-
 tests/functional/qemu_test/config.py | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/functional/meson.build b/tests/functional/meson.build
index b979cff2b9..d34aefa8b0 100644
--- a/tests/functional/meson.build
+++ b/tests/functional/meson.build
@@ -74,7 +74,7 @@ foreach speed : ['quick', 'thorough']
       test_deps += [qemu_img]
     endif
     test_env.set('QEMU_TEST_QEMU_BINARY', test_emulator.full_path())
-    test_env.set('QEMU_BUILD_ROOT', meson.project_build_root())
+    test_env.set('MESON_BUILD_ROOT', meson.project_build_root())
     test_env.set('PYTHONPATH', meson.project_source_root() / 'python:' +
                                meson.current_source_dir())
 
diff --git a/tests/functional/qemu_test/config.py b/tests/functional/qemu_test/config.py
index 6d4c9c3ce1..0192027233 100644
--- a/tests/functional/qemu_test/config.py
+++ b/tests/functional/qemu_test/config.py
@@ -21,7 +21,7 @@ def _source_dir():
     return Path(__file__).parent.parent.parent.parent
 
 def _build_dir():
-    root = os.getenv('QEMU_BUILD_ROOT')
+    root = os.getenv('MESON_BUILD_ROOT')
     if root is not None:
         return Path(root)
     # Makefile.mtest only exists in build dir, so if it is available, use CWD
@@ -32,7 +32,7 @@ def _build_dir():
     if os.path.exists(root):
         return Path(root)
 
-    raise Exception("Cannot identify build dir, set QEMU_BUILD_ROOT")
+    raise Exception("Cannot identify build dir, set MESON_BUILD_ROOT")
 
 BUILD_DIR = _build_dir()
 
-- 
2.53.0

On 10/03/2026 12.47, Daniel P. Berrangé wrote:
> When running functional tests directly there are some heuristics
> to figure out where the build directory lives, along with the
> possibility to override the logic by setting the QEMU_BUILD_DIR
> env variable. This env var is set as part of the test env when
> run via Meson but not when run directly.
> 
> A particular flaw with the currently logic is that it silently
> uses the wrong location when the build directory is a sub-dir
> under "./build", which is a common usage scenario for some devs.
> 
> With the recent introduction of the 'run' script, we now have
> the MESON_BUILD_ROOT env variable set unconditionally, so we
> can rely on that from the functional tests to get the correct
> location in all scenarios.
> 
> Reported-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   tests/functional/meson.build         | 2 +-
>   tests/functional/qemu_test/config.py | 4 ++--
>   2 files changed, 3 insertions(+), 3 deletions(-)

Reviewed-by: Thomas Huth <thuth@redhat.com>