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Mon, 9 Feb 2026 22:14:48 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.65.66]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id C6ACA1800464; Mon, 9 Feb 2026 22:14:46 +0000 (UTC) From: Luiz Capitulino To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com Cc: ryan.roberts@arm.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Subject: [PATCH v2 02/11] mm: introduce pgtable_has_pmd_leaves() Date: Mon, 9 Feb 2026 17:14:24 -0500 Message-ID: In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-MFC-PROC-ID: AmFUy-mqdN14XPksC0p24_1wRpUeSTNOq4E7RiMBaDI_1770675288 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Server: rspam11 X-Stat-Signature: 7ugdit1iudafxw86uprqq7imams6wf4w X-Rspam-User: X-Rspamd-Queue-Id: 9B19F40005 X-HE-Tag: 1770675291-168105 X-HE-Meta: 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 OB/Lf11D hHqI1BoO30LUmIM2gXFVkeSvzeTlMZUYhdAONsR6Y7cV9Jnx161i4GPC5VrMvyQ/1UCUv/pGkJ+2Q61pw0/OroFks0zmf8XJ3lnlq2eGp4BUeJwmlvDv4ucs56JL7GzPWLVcpIgtMz++L+YsoMd3k+hhdvSEigDu5yCDaVVGczCGJwz7eJzJGbSzCwgS9G3srXtTGxktD+MDiMRdWRTG/aoBk83ORbsZMvTz3Az7Ktc2Jpjr1yAeuFOHCISerRUkrc3NOp7XPuhIeA9v1Ba7nLvA9vo9g6ukzjbxfDXOVQho1RBvLcKl8z0g4juUGj2w9cBZdqD4udVRi6Gd6sy27ToSRVfxhiindrebHGbGVpKcJ/oxt5Kdrj0bLBlwTVckmQEM3 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently, we have two helpers that check for PMD-sized pages but have different names and slightly different semantics: - has_transparent_hugepage(): the name suggests it checks if THP is enabled, but when CONFIG_TRANSPARENT_HUGEPAGE=y and the architecture implements this helper, it actually checks if the CPU supports PMD-sized pages - thp_disabled_by_hw(): the name suggests it checks if THP is disabled by the hardware, but it just returns a cached value acquired with has_transparent_hugepage(). This helper is used in fast paths This commit introduces a new helper called pgtable_has_pmd_leaves() which is intended to replace both has_transparent_hugepage() and thp_disabled_by_hw(). pgtable_has_pmd_leaves() has very clear semantics: it returns true if the CPU supports PMD-sized pages and false otherwise. It always returns a cached value, so it can be used in fast paths. The new helper requires an initialization step which is performed by init_arch_has_pmd_leaves(). We call init_arch_has_pmd_leaves() very early during boot in start_kernel() so that users of the API can call it from __setup() handlers. The next commits will convert users of both has_transparent_hugepage() and thp_disabled_by_hw() to pgtable_has_pmd_leaves(). Signed-off-by: Luiz Capitulino --- include/linux/pgtable.h | 7 +++++++ init/main.c | 1 + mm/memory.c | 8 ++++++++ 3 files changed, 16 insertions(+) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 652f287c1ef6..6733f90a1da4 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -2017,6 +2017,13 @@ static inline const char *pgtable_level_to_str(enum pgtable_level level) } } +extern bool __arch_has_pmd_leaves; +static inline bool pgtable_has_pmd_leaves(void) +{ + return __arch_has_pmd_leaves; +} +void __init init_arch_has_pmd_leaves(void); + #endif /* !__ASSEMBLY__ */ #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT) diff --git a/init/main.c b/init/main.c index b84818ad9685..ad1209fffcde 100644 --- a/init/main.c +++ b/init/main.c @@ -1036,6 +1036,7 @@ void start_kernel(void) smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ early_numa_node_init(); boot_cpu_hotplug_init(); + init_arch_has_pmd_leaves(); print_kernel_cmdline(saved_command_line); /* parameters may set static keys */ diff --git a/mm/memory.c b/mm/memory.c index da360a6eb8a4..4c25a3c453c6 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -177,6 +177,14 @@ static int __init init_zero_pfn(void) } early_initcall(init_zero_pfn); +bool __arch_has_pmd_leaves __read_mostly; +EXPORT_SYMBOL(__arch_has_pmd_leaves); + +void __init init_arch_has_pmd_leaves(void) +{ + __arch_has_pmd_leaves = has_transparent_hugepage(); +} + void mm_trace_rss_stat(struct mm_struct *mm, int member) { trace_rss_stat(mm, member); -- 2.53.0