Re: [PATCH v10 20/22] x86: mm: Convert dump_pagetables to use walk_page_range

[Andrew Morton]

On Wed, 7 Aug 2019 13:58:21 +0100 Steven Price <steven.price@xxxxxxx> wrote:

> > ./arch/x86/include/asm/pgtable_64_types.h:56:22: error: initializer element is not constant
> >  #define PTRS_PER_PGD 512
> >                       ^
> 
> This is very unhelpful of GCC - it's actually PTRS_PER_P4D which isn't
> constant!

Well.  You had every right to assume that an all-caps macro is a
compile-time constant.

We are innocent victims of Kirill's c65e774fb3f6af2 ("x86/mm: Make
PGDIR_SHIFT and PTRS_PER_P4D variable") which lazily converted these
macros into runtime-only, under some Kconfig settings.  It should have
changed those macros into static inlined lower-case functions.