[PATCH v3 0/3] Convert 64-bit x86/mm/pat to ptdescs

Vishal Moola (Oracle)
2026-02-02T17:20:20Z

x86/mm/pat should be using ptdescs. One line has already been
converted to pagetable_free(), while the allocation sites use
get_free_pages(). This causes issues separately allocating ptdescs
from struct page.

These patches convert the allocation/free sites to use ptdescs. In
the short term, this helps enable Matthew's work to allocate frozen
pagetables[1]. And in the long term, this will help us cleanly split
ptdesc allocations from struct page.

The pgd_list should also be using ptdescs (for 32bit in this file). This
can be done in a different patchset since there's other users of pgd_list
that still need to be converted.

[1] https://lore.kernel.org/linux-mm/20251113140448.1814860-1-willy@infradead.org/
[2] https://lore.kernel.org/linux-mm/20251020001652.2116669-1-willy@infradead.org/

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I've also tested this on a tree that separately allocates ptdescs. That
didn't find any lingering alloc/free issues.

Based on current mm-new.

v3:
- Move comment regarding 32-bit conversions into the cover letter
- Correct the handling for the pagetable_alloc() error path

Vishal Moola (Oracle) (3):
x86/mm/pat: Convert pte code to use ptdescs
x86/mm/pat: Convert pmd code to use ptdescs
x86/mm/pat: Convert split_large_page() to use ptdescs

arch/x86/mm/pat/set_memory.c | 56 +++++++++++++++++++++---------------
1 file changed, 33 insertions(+), 23 deletions(-)

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2.52.0