Re: [PATCH] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled()

[David Hildenbrand (Arm)]

On 2/11/26 17:35, David Hildenbrand (Arm) wrote:
> On 2/11/26 17:16, Ackerley Tng wrote:
> > "David Hildenbrand (Arm)" <david@xxxxxxxxxx> writes:
> >
> > > Do you have a reproducer? If so, which behavior does it trigger?
> > >
> > > I would assume that we would suddenly have secretmem pages (THP) that
> > > have a directmap. Or some page copy would crash the kernel.
> >
> > Is there a good way to verify from userspace that the directmap hasn't
> > been restored? Should I use CONFIG_PTDUMP_DEBUGFS?
>
> Anything that uses GUP must fail on that secretmem memory. Like doing an 
> O_DIRECT read/write or using vmsplice.

Ah, but that might still fail, because we can identify the page as such.

Hm ... we'd need some introspection interface indeed.

--
Cheers,

David