Re: [PATCH] x86/build: suppress EFI-related tool chain checks upon local $(MAKE) recursion

[Anthony PERARD <anthony.perard@citrix.com>]

On Tue, Sep 21, 2021 at 05:43:38PM +0200, Jan Beulich wrote:
> The xen-syms and xen.efi linking steps are serialized only when the
> intermediate note.o file is necessary. Otherwise both may run in
> parallel. This in turn means that the compiler / linker invocations to
> create efi/check.o / efi/check.efi may also happen twice in parallel.
> Obviously it's a bad idea to have multiple producers of the same output
> race with one another - every once in a while one may e.g. observe
> 
> objdump: efi/check.efi: file format not recognized
> 
> We don't need this EFI related checking to occur when producing the
> intermediate symbol and relocation table objects, and we have an easy
> way of suppressing it: Simply pass in "efi-y=", overriding the
> assignments done in the Makefile and thus forcing the tool chain checks
> to be bypassed.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

> ---
> Obviously the real (but more involved) solution would be to do away with
> the recursive $(MAKE) invocations, by breaking up the long linking
> rules. Representing them instead through multiple smaller rules with
> suitable dependencies is certainly possible (and might even reduce
> redundancy).

There is an alternative to that. Linux have a script which does the kind
of step we do. So maybe doing the same and move the recipe into a script
would work too? This would allow to share the recipe between x86 and Arm
as the link phase of xen-syms is nearly identical. But to avoid calling
make from the script we would have to duplicate the recipe of %.o:%.S.
The xen.efi rules is still x86 only and I don't know whether we could
use the same script as for xen-syms.

I don't know which option would be better those two and the current
state.

Cheers,

-- 
Anthony PERARD