linux-kernel - [PATCH v2 0/3] Convert 64-bit x86/mm/pat to ptdescs

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Message-ID: <20260128224049.385013-1-vishal.moola@gmail.com>
Date: Wed, 28 Jan 2026 14:40:46 -0800
From: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	x86@...nel.org,
	"Mike Rapoport (Microsoft)" <rppt@...nel.org>
Cc: akpm@...ux-foundation.org,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Vishal Moola (Oracle)" <vishal.moola@...il.com>
Subject: [PATCH v2 0/3] Convert 64-bit x86/mm/pat to ptdescs

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.

[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/T/#u

------

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

I've realized that 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.

Based on current mm-new.

v2:
  - Use pagetable_alloc() in populate_pgd() - in patch 2
  - Rename subject line to specify 64-bit (i.e. 32-bit wasn't converted)
  - Added reference links to the projects mentioned in the cover letter

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 | 43 ++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 19 deletions(-)

-- 
2.52.0