arm64/mm: automatically fold contpte mappings

There are situations where a change to a single PTE could cause the
contpte block in which it resides to become foldable (i.e.  could be
repainted with the contiguous bit).  Such situations arise, for example,
when user space temporarily changes protections, via mprotect, for
individual pages, such can be the case for certain garbage collectors.

We would like to detect when such a PTE change occurs.  However this can
be expensive due to the amount of checking required.  Therefore only
perform the checks when an indiviual PTE is modified via mprotect
(ptep_modify_prot_commit() -> set_pte_at() -> set_ptes(nr=1)) and only
when we are setting the final PTE in a contpte-aligned block.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ryan Roberts <[email protected]>
Acked-by: Mark Rutland <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Borislav Petkov (AMD) <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Morse <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions