Re: [PATCH v1 0/4] smaps / mm/gup: fix gup_can_follow_protnone fallout

[David Hildenbrand]

On 31.07.23 21:07, Linus Torvalds wrote:
> On Mon, 31 Jul 2023 at 12:00, David Hildenbrand <david@xxxxxxxxxx> wrote:
> > So in the "!writable" case, we would always call
> > get_user_pages_unlocked() and never honor NUMA faults.
>
> Ok, so kvm doesn't just use the fast version. Oh well. It was an idea..

Certainly an interesting one, thanks for thinking about possible 
alternatives! Unfortunately, KVM is an advanced GUP user to managed 
secondary MMUs.

I'll get the FOLL_HONOR_NUMA_FAULT patches ready tomorrow and we can 
discuss if that looks better.

(btw, the whole reasoning about "HW would refuse to use these pages" was 
exactly the whole reason I went into the FOLL_FORCE direction ... but 
it's really better to make FOLL_FORCE deal with VMA protection only)

--
Cheers,

David / dhildenb