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(host-127-24.cafrjco.fresno.ca.us.clients.pavlovmedia.net. [68.180.127.24]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3081eb95342sm9077739eec.29.2026.06.13.15.15.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 13 Jun 2026 15:15:08 -0700 (PDT) From: Ethan Nelson-Moore To: Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-mm@kvack.org, linux-doc@vger.kernel.org Cc: Ethan Nelson-Moore , Andrew Morton , David Hildenbrand , Jonathan Corbet Subject: [PATCH] docs/mm: describe current criteria for enabling split page table lock for PTE tables Date: Sat, 13 Jun 2026 15:14:47 -0700 Message-ID: <20260613221448.98657-1-enelsonmoore@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The mm documentation regarding split page table lock for PTE tables refers to the CONFIG_SPLIT_PTLOCK_CPUS config option, which was superseded by CONFIG_SPLIT_PTE_PTLOCKS in commit 394290cba966 ("mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLOCKS into Kconfig options"). Update the documentation to refer to the current option and document the situations in which this feature is not supported. Discovered while searching for CONFIG_* symbols referenced in the kernel but not defined in any Kconfig file. Signed-off-by: Ethan Nelson-Moore --- Documentation/mm/split_page_table_lock.rst | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/Documentation/mm/split_page_table_lock.rst b/Documentation/mm/split_page_table_lock.rst index cc3cd46abd1b..c9d16024543b 100644 --- a/Documentation/mm/split_page_table_lock.rst +++ b/Documentation/mm/split_page_table_lock.rst @@ -37,9 +37,12 @@ There are helpers to lock/unlock a table and other accessor functions: - pmd_lockptr() returns pointer to PMD table lock; -Split page table lock for PTE tables is enabled compile-time if -CONFIG_SPLIT_PTLOCK_CPUS (usually 4) is less or equal to NR_CPUS. -If split lock is disabled, all tables are guarded by mm->page_table_lock. +Split page table lock for PTE tables is enabled compile-time (via +CONFIG_SPLIT_PTE_PTLOCKS) if NR_CPUS is greater than or equal to 4 and an +MMU is being used. However, it is not supported on ARM processors with +virtually indexed, physically tagged caches, PA-RISC processors older than +the PA-8000, or 32-bit SPARC processors. If split lock is disabled, all +tables are guarded by mm->page_table_lock. Split page table lock for PMD tables is enabled, if it's enabled for PTE tables and the architecture supports it (see below). -- 2.43.0