Re: [PATCH] mm, virt: merge AS_UNMOVABLE and AS_INACCESSIBLE

[David Hildenbrand]

On 11.07.24 20:03, Paolo Bonzini wrote:
> The flags AS_UNMOVABLE and AS_INACCESSIBLE were both added just for guest_memfd;
> AS_UNMOVABLE is already in existing versions of Linux, while AS_INACCESSIBLE was
> acked for inclusion in 6.11.
>
> But really, they are the same thing: only guest_memfd uses them, at least for
> now, and guest_memfd pages are unmovable because they should not be
> accessed by the CPU.
>
> So merge them into one; use the AS_INACCESSIBLE name which is more comprehensive.
> At the same time, this fixes an embarrassing bug where AS_INACCESSIBLE was used
> as a bit mask, despite it being just a bit index.
>
> The bug was mostly benign, becaus AS_INACCESSIBLE's bit representation (1010)
> corresponded to setting AS_UNEVICTABLE (which is already set) and AS_ENOSPC
> (except no async writes can happen on the guest_memfd).  So the AS_INACCESSIBLE
> flag simply had no effect.
>
> Fixes: 1d23040caa8b ("KVM: guest_memfd: Use AS_INACCESSIBLE when creating guest_memfd inode")
> Fixes: c72ceafbd12c ("mm: Introduce AS_INACCESSIBLE for encrypted/confidential memory")
> Cc: linux-mm@xxxxxxxxx

Yeah, if we have to bring back the separation in the future, we can 
revisit that.

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb