Re: [PATCH -next] memregion: Add arch_flush_memregion() interface

[Davidlohr Bueso]

On Wed, 07 Sep 2022, Borislav Petkov wrote:

> On Mon, Aug 29, 2022 at 02:29:18PM -0700, Davidlohr Bueso wrote:
> > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> > index 1abd5438f126..18463cb704fb 100644
> > --- a/arch/x86/mm/pat/set_memory.c
> > +++ b/arch/x86/mm/pat/set_memory.c
> > @@ -330,6 +330,20 @@ void arch_invalidate_pmem(void *addr, size_t size)
> >  EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
> >  #endif
> >
> > +#ifdef CONFIG_ARCH_HAS_MEMREGION_INVALIDATE
> > +bool arch_has_flush_memregion(void)
> > +{
> > +	return !cpu_feature_enabled(X86_FEATURE_HYPERVISOR);
>
> This looks really weird. Why does this need to care about HV at all?

So the context here is:

e2efb6359e62 ("ACPICA: Avoid cache flush inside virtual machines")

> Does that nfit stuff even run in guests?

No, nor does cxl. This was mostly in general a precautionary check such
that the api is unavailable in VMs.

> > +EXPORT_SYMBOL(arch_has_flush_memregion);
>
> ...
>
> > +EXPORT_SYMBOL(arch_flush_memregion);
>
> Why aren't those exports _GPL?

Fine by me.

Thanks,
Davidlohr