Re: [PATCH v24 16/30] mm: Fixup places that call pte_mkwrite() directly

[Kirill A. Shutemov]

On Thu, Apr 01, 2021 at 03:10:50PM -0700, Yu-cheng Yu wrote:
> When serving a page fault, maybe_mkwrite() makes a PTE writable if it is in
> a writable vma.  A shadow stack vma is writable, but its PTEs need
> _PAGE_DIRTY to be set to become writable.  For this reason, maybe_mkwrite()
> has been updated.
> 
> There are a few places that call pte_mkwrite() directly, but have the
> same result as from maybe_mkwrite().  These sites need to be updated for
> shadow stack as well.  Thus, change them to maybe_mkwrite():
> 
> - do_anonymous_page() and migrate_vma_insert_page() check VM_WRITE directly
>   and call pte_mkwrite(), which is the same as maybe_mkwrite().  Change
>   them to maybe_mkwrite().
> 
> - In do_numa_page(), if the numa entry was writable, then pte_mkwrite()
>   is called directly.  Fix it by doing maybe_mkwrite().
> 
> - In change_pte_range(), pte_mkwrite() is called directly.  Replace it with
>   maybe_mkwrite().
> 
>   A shadow stack vma is writable but has different vma
> flags, and handled accordingly in maybe_mkwrite().
> 

Have you checked THP side? Looks like at least do_huge_pmd_numa_page()
needs adjustment, no?

-- 
 Kirill A. Shutemov