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Message-ID: <cd96d70b-1eb3-494a-912a-52d479e3df87@csgroup.eu>
Date: Tue, 10 Jun 2025 09:33:47 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Andrew Donnellan <ajd@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org
Cc: x86@...nel.org, linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
pasha.tatashin@...een.com, sweettea-kernel@...miny.me
Subject: Re: [PATCH v14 00/11] Support page table check on PowerPC
Le 11/04/2025 à 07:43, Andrew Donnellan a écrit :
> Support page table check on all PowerPC platforms. This works by
> serialising assignments, reassignments and clears of page table
> entries at each level in order 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 stubs must be
> defined for all powerpc platforms. Additionally, separate set_pte_at()
> and set_pte_at_unchecked(), to allow for internal, uninstrumented mappings.
>
> (This series was written by Rohan McLure, who has left IBM and is no longer
> working on powerpc.)
This series requires a rebase after commit 91e40668e70a
("mm/page_table_check: Batch-check pmds/puds just like ptes")
Christophe
>
> v14:
> * Fix a call to page_table_check_pud_set() that was missed (akpm)
>
> v13:
> * Rebase on mainline
> * Don't use set_pte_at_unchecked() for early boot purposes (Pasha)
> Link: https://lore.kernel.org/linuxppc-dev/20250211161404.850215-1-ajd@linux.ibm.com/
>
> v12:
> * Rename commits that revert changes to instead reflect that we are
> reinstating old behaviour due to it providing more flexibility
> * Add return line to pud_pfn() stub
> * Instrument ptep_get_and_clear() for nohash
> Link: https://lore.kernel.org/linuxppc-dev/20240402051154.476244-1-rmclure@linux.ibm.com/
>
> v11:
> * The pud_pfn() stub, which previously had no legitimate users on any
> powerpc platform, now has users in Book3s64 with transparent pages.
> Include a stub of the same name for each platform that does not
> define their own.
> * Drop patch that standardised use of p*d_leaf(), as already included
> upstream in v6.9.
> * Provide fallback definitions of p{m,u}d_user_accessible_page() that
> do not reference p*d_leaf(), p*d_pte(), as they are defined after
> powerpc/mm headers by linux/mm headers.
> * Ensure that set_pte_at_unchecked() has the same checks as
> set_pte_at().
> Link: https://lore.kernel.org/linuxppc-dev/20240328045535.194800-14-rmclure@linux.ibm.com/
>
> v10:
> * Revert patches that removed address and mm parameters from page table
> check routines, including consuming code from arm64, x86_64 and
> riscv.
> * Implement *_user_accessible_page() routines in terms of pte_user()
> where available (64-bit, book3s) but otherwise by checking the
> address (on platforms where the pte does not imply whether the
> mapping is for user or kernel)
> * Internal set_pte_at() calls replaced with set_pte_at_unchecked(), which
> is identical, but prevents double instrumentation.
> Link: https://lore.kernel.org/linuxppc-dev/20240313042118.230397-9-rmclure@linux.ibm.com/T/
>
> v9:
> * Adapt to using the set_ptes() API, using __set_pte_at() where we need
> must avoid instrumentation.
> * Use the logic of *_access_permitted() for implementing
> *_user_accessible_page(), which are required routines for page table
> check.
> * Even though we no longer need p{m,u,4}d_leaf(), still default
> implement these to assist in refactoring out extant
> p{m,u,4}_is_leaf().
> * Add p{m,u}_pte() stubs where asm-generic does not provide them, as
> page table check wants all *user_accessible_page() variants, and we
> would like to default implement the variants in terms of
> pte_user_accessible_page().
> * Avoid the ugly pmdp_collapse_flush() macro nonsense! Just instrument
> its constituent calls instead for radix and hash.
> Link: https://lore.kernel.org/linuxppc-dev/20231130025404.37179-2-rmclure@linux.ibm.com/
>
> v8:
> * Fix linux/page_table_check.h include in asm/pgtable.h breaking
> 32-bit.
> Link: https://lore.kernel.org/linuxppc-dev/20230215231153.2147454-1-rmclure@linux.ibm.com/
>
> v7:
> * Remove use of extern in set_pte prototypes
> * Clean up pmdp_collapse_flush macro
> * Replace set_pte_at with static inline function
> * Fix commit message for patch 7
> Link: https://lore.kernel.org/linuxppc-dev/20230215020155.1969194-1-rmclure@linux.ibm.com/
>
> v6:
> * Support huge pages and p{m,u}d accounting.
> * Remove instrumentation from set_pte from kernel internal pages.
> * 64s: Implement pmdp_collapse_flush in terms of __pmdp_collapse_flush
> as access to the mm_struct * is required.
> Link: https://lore.kernel.org/linuxppc-dev/20230214015939.1853438-1-rmclure@linux.ibm.com/
>
> v5:
> Link: https://lore.kernel.org/linuxppc-dev/20221118002146.25979-1-rmclure@linux.ibm.com/
>
> Rohan McLure (11):
> mm/page_table_check: Reinstate address parameter in
> [__]page_table_check_pud_set()
> mm/page_table_check: Reinstate address parameter in
> [__]page_table_check_pmd_set()
> mm/page_table_check: Provide addr parameter to
> page_table_check_pte_set()
> mm/page_table_check: Reinstate address parameter in
> [__]page_table_check_pud_clear()
> mm/page_table_check: Reinstate address parameter in
> [__]page_table_check_pmd_clear()
> mm/page_table_check: Reinstate address parameter in
> [__]page_table_check_pte_clear()
> mm: Provide address parameter to p{te,md,ud}_user_accessible_page()
> powerpc: mm: Add pud_pfn() stub
> powerpc: mm: Implement *_user_accessible_page() for ptes
> powerpc: mm: Use set_pte_at_unchecked() for internal usages
> powerpc: mm: Support page table check
>
> arch/arm64/include/asm/pgtable.h | 18 +++---
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/book3s/32/pgtable.h | 12 +++-
> arch/powerpc/include/asm/book3s/64/pgtable.h | 62 +++++++++++++++---
> arch/powerpc/include/asm/nohash/pgtable.h | 13 +++-
> arch/powerpc/include/asm/pgtable.h | 19 ++++++
> arch/powerpc/mm/book3s64/hash_pgtable.c | 4 ++
> arch/powerpc/mm/book3s64/pgtable.c | 17 +++--
> arch/powerpc/mm/book3s64/radix_pgtable.c | 9 ++-
> arch/powerpc/mm/pgtable.c | 12 ++++
> arch/riscv/include/asm/pgtable.h | 18 +++---
> arch/x86/include/asm/pgtable.h | 22 +++----
> include/linux/page_table_check.h | 67 ++++++++++++--------
> include/linux/pgtable.h | 10 +--
> mm/page_table_check.c | 39 +++++++-----
> 15 files changed, 226 insertions(+), 97 deletions(-)
>
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