Re: [RFC PATCH v2 34/47] hugetlb: userfaultfd: add support for high-granularity UFFDIO_CONTINUE

[James Houghton]

On Fri, Dec 23, 2022 at 1:38 PM Peter Xu <peterx@xxxxxxxxxx> wrote:
>
> James,
>
> On Fri, Oct 21, 2022 at 04:36:50PM +0000, James Houghton wrote:
> > +     bool use_hgm = uffd_ctx_has_hgm(&dst_vma->vm_userfaultfd_ctx) &&
> > +             mode == MCOPY_ATOMIC_CONTINUE;
>
> Do you think in your new version use_hgm can work even for MISSING by
> default?

I don't think so -- UFFDIO_COPY will allocate a hugepage, so I'm not
sure if it makes sense to allow it at high-granularity. If UFFDIO_COPY
didn't allocate a new page, then it could make sense (maybe we'd need
a new ioctl or new UFFDIO_COPY mode?). I think it makes most sense to
add this with another series.

Thanks,
- James