On Wed, Oct 14, 2020 at 08:45:37AM -0700, Andy Lutomirski wrote:
> On Wed, Oct 14, 2020 at 1:33 AM Ankur Arora <ankur.a.arora@xxxxxxxxxx> wrote:
> >
> > Define clear_page_uncached() as an alternative_call() to clear_page_nt()
> > if the CPU sets X86_FEATURE_NT_GOOD and fallback to clear_page() if it
> > doesn't.
> >
> > Similarly define clear_page_uncached_flush() which provides an SFENCE
> > if the CPU sets X86_FEATURE_NT_GOOD.
>
> As long as you keep "NT" or "MOVNTI" in the names and keep functions
> in arch/x86, I think it's reasonable to expect that callers understand
> that MOVNTI has bizarre memory ordering rules. But once you give
> something a generic name like "clear_page_uncached" and stick it in
> generic code, I think the semantics should be more obvious.
Why does it have to be a separate call? Why isn't it behind the
clear_page() alternative machinery so that the proper function is
selected at boot? IOW, why does a user of clear_page functionality need
to know at all about an "uncached" variant?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
