Re: [RFC PATCH 0/9] tests: run python tests under the build/tests/venv environment

[Paolo Bonzini <pbonzini@redhat.com>]

On 5/13/22 10:35, Daniel P. Berrangé wrote:
> The tests is an area where we still have too much taking place in
> Makefiles, as opposed to meson. Can we put a rule in
> tests/meson.build to trigger the ven creation ? Gets us closer to
> being able to run ninja without using make as a wrapper.

I don't think this is or even should be a goal, because we have multiple 
projects under the QEMU tree:

- the QEMU binaries proper (emulators, tools, etc.)

- the firmware (pc-bios/{vof,s390-ccw,optionrom} with sources, the rest 
as submodules)

- tests/tcg


Each of these has its own build system and it's not possible to unify 
them under a single meson-based build:

- tests/tcg supports cross compilation for a different target, and 
pc-bios/ firmware will soon follow suit (which is why these directories 
haven't been converted to Meson, even though patches exist)

- firmware outside pc-bios/ consists of many external projects each with 
its own build system; right now it is not even buildable except by magic 
invocations that no one really knows

On top of this, there's support for building Docker images for 
cross-compilation which obviously doesn't fit the Meson usecases either.

In other words, Meson is the build system for QEMU *executables* (and 
that's why tests for the QEMU executables are being moved from configure 
to meson), but not for QEMU as a whole.


So I don't expect configure and Make to disappear.  Meson is great at 
building a C program as big as QEMU; but QEMU is not just a C program, 
and isolating the C parts into Meson lets Make handle the rest of the 
complexity better than before, for example with cross compiled firmware 
support.

Likewise, we're now using "meson test" for "make check" and a custom 
runner for "make check-block"; but perhaps one day Avocado could replace 
both runners via custom Avocado resolvers (basically JSON emitters 
similar to Meson introspection data).  That of course depends on whether 
Avocado has feature parity with "meson test".

Paolo