Re: [PATCH 2/4] mm: introduce new VM_NOZEROPAGE flag

Paolo Bonzini
2014-10-20T18:14:53Z

On 10/18/2014 06:28 PM, Dave Hansen wrote:
> > Currently it is an all or nothing thing, but for a future change we might want to just
> > tag the guest memory instead of the complete user address space.
>
> I think it's a bad idea to reserve a flag for potential future use. If
> you_need_ it in the future, let's have the discussion then. For now, I
> think it should probably just be stored in the mm somewhere.

I agree with Dave (I thought I disagreed, but I changed my mind while
writing down my thoughts). Just define mm_forbids_zeropage in
arch/s390/include/asm, and make it return mm->context.use_skey---with a
comment explaining how this is only for processes that use KVM, and then
only for guests that use storage keys.

Paolo (who was just taught what storage keys really are)