Re: [RFC PATCH] tests/vm: avoid re-building the VM images all the time

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Feb 26, 2024 at 05:46:39PM +0000, Alex Bennée wrote:
> There are two problems.
> 
> The first is a .PHONY target will always evaluate which triggers a
> full re-build of the VM images. Drop the requirement knowing that this
> introduces a manual step on freshly configure build dirs.

For context, the background to this is:

   https://gitlab.com/qemu-project/qemu/-/issues/2118

dropping '$(VM_VENV)' is the fix for that bit, which is the real
killer bit.

> 
> The second is a minor unrelated tweak to the Makefile also triggers an
> expensive full re-build. Solve this be avoiding the dependency and
> putting a comment just above the bit that matters and hope developers
> notice the comment.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> 
> ---
> 
> This is hacky and sub-optimal. There surely must be a way to have our cake
> and eat it?
> ---
>  tests/vm/Makefile.include | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tests/vm/Makefile.include b/tests/vm/Makefile.include
> index bf12e0fa3c5..a109773c588 100644
> --- a/tests/vm/Makefile.include
> +++ b/tests/vm/Makefile.include
> @@ -88,10 +88,11 @@ vm-build-all: $(addprefix vm-build-, $(IMAGES))
>  vm-clean-all:
>  	rm -f $(IMAGE_FILES)
>  
> +# Rebuilding the VMs every time this Makefile is tweaked is very
> +# expensive for most users. If you tweak the recipe bellow you will
> +# need to manually zap $(IMAGES_DIR)/%.img to rebuild.
>  $(IMAGES_DIR)/%.img:	$(SRC_PATH)/tests/vm/% \
> -			$(SRC_PATH)/tests/vm/basevm.py \
> -			$(SRC_PATH)/tests/vm/Makefile.include \
> -			$(VM_VENV)
> +			$(SRC_PATH)/tests/vm/basevm.py
>  	@mkdir -p $(IMAGES_DIR)
>  	$(call quiet-command, \
>  		$(VM_PYTHON) $< \
> -- 
> 2.39.2
> 
> 

With regards,
Daniel
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