From nobody Wed Feb 11 07:07:35 2026 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 2FBE260892 for ; Wed, 6 Mar 2024 10:43:45 +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=1709721826; cv=none; b=HvE5Rb8YRNYKpJ8Pn0WwyLKhn/VWHcTSSPmENKUY1rjNtc86KuT6MgqW8YfXC0u4dfc5B0LYufXNO4TzQNTJC27/Nn2A6980O442YvVtPKA6FSEPy6xohBUt72sr8K4ctcPgbUMOLLxEgbz9mgcrHTvc+OVXJ1fz22E94tXVTaw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709721826; c=relaxed/simple; bh=c49fwyRKoS6wfKvCgxkRGT+RfTOSzCUnQcMvkubeAHI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=K4FH3N/gpcSw322YZ2XXYSgIqyUhB0k42jjo8ZQ+sUwuoOg+ISNfMBdbccGBBXvjhqhfsnVChQ3FHbvnMgloSpUbl34yD9q56her5z0N7t2cy8+cDWpEf0Siowh6ojDA8xqlgk8OZ17WFKzEqBrBIt6dIN1D4lXdN2AfezlY3Tg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=JnPj9dUJ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="JnPj9dUJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709721824; 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=EszM++ZyWA4F0AEHMeW0S6yDLENEL5nIwjErtg69nlA=; b=JnPj9dUJW5civc0vmQUjHJKZzGo0vQZZR6gTdJEWqfRLQUfq02sW485cSNUBjWHRwjaJ7H h3henowujFD0mx6HvPDDmfstYJrKOzXAYymjS6RDZ38EGorX6rE2YDRqaotcndbB8a+pKe dOBv4blpPYNuOblsUFhnwUVLppuClks= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-122-so8_Bz8AP0eINzkAwxTEYA-1; Wed, 06 Mar 2024 05:43:38 -0500 X-MC-Unique: so8_Bz8AP0eINzkAwxTEYA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0BD8284B0C5; Wed, 6 Mar 2024 10:43:38 +0000 (UTC) Received: from x1n.redhat.com (unknown [10.72.116.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id A13A3111DD02; Wed, 6 Mar 2024 10:43:31 +0000 (UTC) From: peterx@redhat.com To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, Andrew Morton , Muchun Song , Jason Gunthorpe , peterx@redhat.com, Matthew Wilcox , Mike Rapoport , Christophe Leroy , x86@kernel.org, sparclinux@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH RFC 13/13] mm: Document pXd_leaf() API Date: Wed, 6 Mar 2024 18:41:47 +0800 Message-ID: <20240306104147.193052-14-peterx@redhat.com> In-Reply-To: <20240306104147.193052-1-peterx@redhat.com> References: <20240306104147.193052-1-peterx@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 Content-Type: text/plain; charset="utf-8" From: Peter Xu There's one small section already, but since we're going to remove pXd_huge(), that comment may start to obsolete. Rewrite that section with more information, hopefully with that the API is crystal clear on what it implies. Signed-off-by: Peter Xu Reviewed-by: Jason Gunthorpe --- include/linux/pgtable.h | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 85fc7554cd52..6b0d222a7fad 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1770,11 +1770,25 @@ typedef unsigned int pgtbl_mod_mask; #endif =20 /* - * p?d_leaf() - true if this entry is a final mapping to a physical addres= s. - * This differs from p?d_huge() by the fact that they are always available= (if - * the architecture supports large pages at the appropriate level) even - * if CONFIG_HUGETLB_PAGE is not defined. - * Only meaningful when called on a valid entry. + * pXd_leaf() is the API to check whether a pgtable entry is a huge page + * mapping. It should work globally across all archs, without any + * dependency on CONFIG_* options. For architectures that do not support + * huge mappings on specific levels, below fallbacks will be used. + * + * A leaf pgtable entry should always imply the following: + * + * - It is a "present" entry. IOW, before using this API, please check it + * with pXd_present() first. NOTE: it may not always mean the "present + * bit" is set. For example, PROT_NONE entries are always "present". + * + * - It should _never_ be a swap entry of any type. Above "present" check + * should have guarded this, but let's be crystal clear on this. + * + * - It should contain a huge PFN, which points to a huge page larger than + * PAGE_SIZE of the platform. The PFN format isn't important here. + * + * - It should cover all kinds of huge mappings (e.g., pXd_trans_huge(), + * pXd_devmap(), or hugetlb mappings). */ #ifndef pgd_leaf #define pgd_leaf(x) false --=20 2.44.0