From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7C6D022F74A for ; Fri, 1 May 2026 19:20:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777663213; cv=none; b=DAFwFocd07p6fPvoz5JDllspw5xjEVUU0IpgSY7Kgb4dZa5BKJmOt65IYrX4MXbPVf5y6iDuLbcjdasybJpysAEFcyy0FGdOq2Mi5F7ocE0hKqtWqVttm8dQX7jzgHi5hkKFI1aSH7nW/H8DSWm7pygDWGjNXUz2nbJ2Cks2+Lw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777663213; c=relaxed/simple; bh=kNi+A3EXVIa4kqYnoxI9MSr7lrqwHIEixTG8lQVV5r8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fswdNHE3iDAOScKlNZRu5S7+EHwrvBnq0wsupbrjE3B7gO/neG3TAGvmbfM33X0yG2yET7PVVTtK0jnon7/HEupQyREnf7rM569KzHHD20rA4T11Lxm9QprH7ByHcpqUGOBIxMMIFD04GiRk73uYHvM1xnNjKlNLAjlL3jpezwU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=GHgqArs1; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GHgqArs1" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777663211; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wm/3tKpS1+bbbkiWPW54qthE5IZvUCs3az7WMfHFyEE=; b=GHgqArs1zKPccLUSMs7rmLUTeWqTshQ7wIceRuwvY8moNWA3rGLv0nWnp90uZQk4fa6bJD l+dt/hUm87I9Ojcd8+ENE6L84qMzZlI08IVCrtu37vU0qged8uXruqcDvldJohPvDiZW8F vZes7hGVkFA3gu8HTGmWcYFaiWyUhk8= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-558-EPxmSzN4OfyvKHGpT8koQQ-1; Fri, 01 May 2026 15:20:06 -0400 X-MC-Unique: EPxmSzN4OfyvKHGpT8koQQ-1 X-Mimecast-MFC-AGG-ID: EPxmSzN4OfyvKHGpT8koQQ_1777663204 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B63AD19560B5; Fri, 1 May 2026 19:20:03 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.64.126]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4CD791800577; Fri, 1 May 2026 19:20:00 +0000 (UTC) From: Luiz Capitulino To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com, ziy@nvidia.com, lance.yang@linux.dev Cc: corbet@lwn.net, tsbogend@alpha.franken.de, maddy@linux.ibm.com, mpe@ellerman.id.au, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, x86@kernel.org, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Subject: [PATCH v4 2/9] mm: introduce pgtable_has_pmd_leaves() Date: Fri, 1 May 2026 15:18:44 -0400 Message-ID: <2a0bae00cdd2b6ef6b962610b523ebfc97806ba7.1777663129.git.luizcap@redhat.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 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() early during boot in start_kernel() right after parse_early_param() but before parse_args(). This allows early_param() handlers to change CPU flags if needed (eg. parse_memopt() in x86-32) while also allowing users to use the API 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 | 15 +++++++++++++++ init/main.c | 1 + mm/memory.c | 9 +++++++++ 3 files changed, 25 insertions(+) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index cdd68ed3ae1a..b365be3516bf 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -2243,6 +2243,21 @@ static inline const char *pgtable_level_to_str(enum pgtable_level level) } } +#ifdef CONFIG_MMU +DECLARE_STATIC_KEY_TRUE(__arch_has_pmd_leaves_key); +static inline bool pgtable_has_pmd_leaves(void) +{ + return static_branch_likely(&__arch_has_pmd_leaves_key); +} +void __init init_arch_has_pmd_leaves(void); +#else +static inline bool pgtable_has_pmd_leaves(void) +{ + return false; +} +static inline void __init init_arch_has_pmd_leaves(void) { } +#endif + #endif /* !__ASSEMBLY__ */ #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT) diff --git a/init/main.c b/init/main.c index 96f93bb06c49..eea7c5bdddf7 100644 --- a/init/main.c +++ b/init/main.c @@ -1053,6 +1053,7 @@ void start_kernel(void) print_kernel_cmdline(saved_command_line); /* parameters may set static keys */ parse_early_param(); + init_arch_has_pmd_leaves(); after_dashes = parse_args("Booting kernel", static_command_line, __start___param, __stop___param - __start___param, diff --git a/mm/memory.c b/mm/memory.c index ea6568571131..90b2d9e84320 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -164,6 +164,15 @@ __setup("norandmaps", disable_randmaps); unsigned long highest_memmap_pfn __read_mostly; +DEFINE_STATIC_KEY_TRUE(__arch_has_pmd_leaves_key); +EXPORT_SYMBOL(__arch_has_pmd_leaves_key); + +void __init init_arch_has_pmd_leaves(void) +{ + if (!has_transparent_hugepage()) + static_branch_disable(&__arch_has_pmd_leaves_key); +} + void mm_trace_rss_stat(struct mm_struct *mm, int member) { trace_rss_stat(mm, member); -- 2.53.0