On Thu, Dec 18, 2025 at 12:10 PM Andrew Donnellan [off-list ref] wrote:

[I will be leaving IBM in about a month from now, and will also be on leave
for most of that time starting tomorrow. I've cc'd my personal email, which
I am going to use for any kernel development I do after I leave, and also
Srish Srinivasan, who will be taking over some of my work.]

Support page table check on PowerPC. Page table check tracks the usage of
of page table entries at each level to ensure that anonymous mappings have
at most one writable consumer, and likewise that file-backed mappings are
not simultaneously also anonymous mappings.

In order to support this infrastructure, a number of helpers or stubs must be
defined or updated for all powerpc platforms. Additionally, we separate
set_pte_at() and set_pte_at_unchecked(), to allow for internal, uninstrumented
mappings.

On some PowerPC platforms, implementing {pte,pmd,pud}_user_accessible_page()
requires the address. We revert previous changes that removed the address
parameter from various interfaces, and add it to some other interfaces,
in order to allow this.

For now, we don't allow page table check alongside HUGETLB_PAGE, due to the
arch-specific complexity of set_huge_page_at(). (I'm sure I could figure
this out, but I have to get this version on this list before I leave my job.)

This series was initially written by Rohan McLure, who has left IBM and
is no longer working on powerpc.

v18:
 * Rebase on mm-new
 * Add instrumentation for pudp_invalidate()
 * Add cleanup patch to use pte_advance_pfn()
 * Move p{m,u}d_user_accessible_page() to a more sensible place in the code
 * Disable when HUGETLB_PAGE is enabled

Thank you. This series looks good to me.

Pasha