Re: [PATCH v1 0/2] mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()

[Peter Xu]

On Thu, Dec 22, 2022 at 04:17:22PM -0500, Peter Xu wrote:
> On Thu, Dec 22, 2022 at 09:55:09PM +0100, David Hildenbrand wrote:
> > Playing with virtio-mem and background snapshots (using uffd-wp) on
> > hugetlb in QEMU, I managed to trigger a VM_BUG_ON(). Looking into the
> > details, hugetlb_change_protection() seems to not handle uffd-wp correctly
> > in all cases.
> > 
> > Patch #1 fixes my test case. I don't have reproducers for patch #2, as
> > it requires running into migration entries.
> > 
> > I did not yet check in detail yet if !hugetlb code requires similar care.

Ah I should have left a message here but I forgot - afaict shmem is all fine.

> > 
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > Cc: Peter Xu <peterx@xxxxxxxxxx>
> > Cc: Muchun Song <muchun.song@xxxxxxxxx>
> > Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> > 
> > David Hildenbrand (2):
> >   mm/hugetlb: fix PTE marker handling in hugetlb_change_protection()
> >   mm/hugetlb: fix uffd-wp handling for migration entries in
> >     hugetlb_change_protection()
> 
> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> 
> Thanks, David.
> 
> -- 
> Peter Xu

-- 
Peter Xu