* Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote:
> On Mon, Oct 07, 2019 at 03:06:17PM +0200, Ingo Molnar wrote:
> >
> > * Anshuman Khandual <anshuman.khandual@xxxxxxx> wrote:
> >
> > > This adds a test module which will validate architecture page table helpers
> > > and accessors regarding compliance with generic MM semantics expectations.
> > > This will help various architectures in validating changes to the existing
> > > page table helpers or addition of new ones.
> > >
> > > Test page table and memory pages creating it's entries at various level are
> > > all allocated from system memory with required alignments. If memory pages
> > > with required size and alignment could not be allocated, then all depending
> > > individual tests are skipped.
> >
> > > diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
> > > index 52e5f5f2240d..b882792a3999 100644
> > > --- a/arch/x86/include/asm/pgtable_64_types.h
> > > +++ b/arch/x86/include/asm/pgtable_64_types.h
> > > @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void)
> > > #define pgtable_l5_enabled() 0
> > > #endif /* CONFIG_X86_5LEVEL */
> > >
> > > +#define mm_p4d_folded(mm) (!pgtable_l5_enabled())
> > > +
> > > extern unsigned int pgdir_shift;
> > > extern unsigned int ptrs_per_p4d;
> >
> > Any deep reason this has to be a macro instead of proper C?
>
> It's a way to override the generic mm_p4d_folded(). It can be rewritten
> as inline function + define. Something like:
>
> #define mm_p4d_folded mm_p4d_folded
> static inline bool mm_p4d_folded(struct mm_struct *mm)
> {
> return !pgtable_l5_enabled();
> }
>
> But I don't see much reason to be more verbose here than needed.
C type checking? Documentation? Yeah, I know it's just a one-liner, but
the principle of the death by a thousand cuts applies here.
BTW., any reason this must be in the low level pgtable_64_types.h type
header, instead of one of the API level header files?
Thanks,
Ingo
