Ping: [PATCH RFC] build: respect top-level .config also for out-of-tree hypervisor builds

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.03.2023 15:58, Jan Beulich wrote:
> With in-tree builds Config.mk includes a .config file (if present) from
> the top-level directory. Similar functionality is wanted with out-of-
> tree builds. Yet the concept of "top-level directory" becomes fuzzy in
> that case, because there is not really a requirement to have identical
> top-level directory structure in the output tree; in fact there's no
> need for anything top-level-ish there. Look for such a .config, but only
> if the tree layout matches (read: if the directory we're building in is
> named "xen").
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> RFC: The directory name based heuristic of course isn't nice. But I
>      couldn't think of anything better. Suggestions?
> 
> RFC: There also being a .config in the top-level source dir would be a
>      little problematic: It would be included _after_ the one in the
>      object tree. Yet if such a scenario is to be expected/supported at
>      all, it makes more sense the other way around.

Anyone? I'm certainly okay for my approach to be rejected, but I'd like
to see out-of-tree builds to reach functional parity with in-tree ones.

Jan

> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -236,8 +236,17 @@ endif
>  
>  include scripts/Kbuild.include
>  
> -# Don't break if the build process wasn't called from the top level
> -# we need XEN_TARGET_ARCH to generate the proper config
> +# Don't break if the build process wasn't called from the top level.  We need
> +# XEN_TARGET_ARCH to generate the proper config.  If building outside of the
> +# source tree also check whether we need to include a "top-level" .config:
> +# Config.mk, using $(XEN_ROOT)/.config, would look only in the source tree.
> +ifeq ($(building_out_of_srctree),1)
> +# Try to avoid including a random unrelated .config: Assume our parent dir
> +# is a "top-level" one only when the objtree is .../xen.
> +ifeq ($(patsubst %/xen,,$(abs_objtree)),)
> +-include ../.config
> +endif
> +endif
>  include $(XEN_ROOT)/Config.mk
>  
>  # Set ARCH/SUBARCH appropriately.
> --- a/xen/Rules.mk
> +++ b/xen/Rules.mk
> @@ -17,6 +17,13 @@ __build:
>  
>  -include $(objtree)/include/config/auto.conf
>  
> +# See commentary around the similar contruct in Makefile.
> +ifneq ($(abs_objtree),$(abs_srctree))
> +ifeq ($(patsubst %/xen,,$(abs_objtree)),)
> +../.config: ;
> +-include ../.config
> +endif
> +endif
>  include $(XEN_ROOT)/Config.mk
>  include $(srctree)/scripts/Kbuild.include
>  
>