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

Dave Hansen
2014-10-18T16:28:17Z

On 10/18/2014 07:49 AM, Dominik Dingel wrote:
> On Fri, 17 Oct 2014 15:04:21 -0700
> Dave Hansen <dave.hansen@intel.com> wrote:
>> Is there ever a time where the VMAs under an mm have mixed VM_NOZEROPAGE
>> status? Reading the patches, it _looks_ like it might be an all or
>> nothing thing.
>
> 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.

>> Full disclosure: I've got an x86-specific feature I want to steal a flag
>> for. Maybe we should just define another VM_ARCH bit.
>>
>
> So you think of something like:
>
> #if defined(CONFIG_S390)
> # define VM_NOZEROPAGE VM_ARCH_1
> #endif
>
> #ifndef VM_NOZEROPAGE
> # define VM_NOZEROPAGE VM_NONE
> #endif
>
> right?

Yeah, something like that.