From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E4572547044; Thu, 1 Oct 2026 13:18:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790860721; cv=none; b=uGFbyisuqXKAI7o9CBKSb/XNW81H2SVhdtG32zJ30/vWj9TriZi3ySosXwGcKWzs7AmJ3B+4YDitHQlJhocOzjgzDF9aWzFZNQ9f+L6ZtgwxrnvMfl9sQqNgTycEOAxlgRw0phunuoJalYzHDObhg8C82vzpan7o/8dKl0phm28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790860721; c=relaxed/simple; bh=JkI7VZ4A2uC+/dn/L/W5qEz5CiiPheGQnlanGKaUISA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ETcJ1NcbHqBgpF6IYf+BqSLH5Q39PI3LRPFC36l+haeIC9pjh4HHzbN8cuH5IYH29UnW8LP8d5t2qlMWfZjNhUTSuVyDMnrlTD4BwkMAAhYhSWlkAk9kSFUq671GPknSMJW1mDMx/OvoiwBXoAimx14GHxEdmJKErvSOqw4nbOQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=agBhyH+b; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="agBhyH+b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 628371F000FF; Thu, 1 Oct 2026 13:18:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790860718; bh=UxjpaonxC/3VDFbLXavStYHgpCVIO4MBlBHvzTk6YXI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=agBhyH+bFmKD1JiAnoEtz/5qMdv8Ap+ND3x/3N77sLFcXCZ3bcDlajbZP+2ap44sx KPIQ+CdPX8Cd2RQc2lWaQ+6tuTQVHD2pYQlPNxdOxQthGqM2hpE/FWfeBE+JBoOiSg aTHw3Pfaa+usXhHmYbPmjg6Em6hcDF+IY/Dz4XEOgO3LkcfaH27mJOMvaKWNKyUSaV dIgxHpJeU+ZOW+vHFYouo/WQFX/mh6XCActsubBMgSttDFWHcozj2biVdd0OlH5rHg SjqdUVy0SHAv0dkWibepFp4IukMLRAR7jxSvh/uVcF78zQKMLBluxXYPcqcH563yw/ oK2yZa6XGh3Fg== Message-ID: <0623ee06-00e5-421e-a24a-ed605abb559b@kernel.org> Date: Thu, 1 Oct 2026 14:36:40 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 15/40] mm/vma: add vma[_flags]_is_kernel_owned() predicates To: "Lorenzo Stoakes (ARM)" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Greg Kroah-Hartman , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Paul Moore , Stephen Smalley , Jaroslav Kysela , Takashi Iwai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Doug Gilbert , "James E.J. Bottomley" , "Martin K. 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Miller" , Andreas Larsson , Alexander Viro , Christian Brauner , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , Johannes Weiner , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chengming Zhou , Michal Hocko , Miklos Szeredi , Xu Xin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-usb@vger.kernel.org, linux-rdma@vger.kernel.org, selinux@vger.kernel.org, linux-sound@vger.kernel.org, bpf@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, fuse-devel@lists.linux.dev References: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> <20260917-b4-mmap-prepare-vma-flag-sanify-v3-15-4583d8a23bca@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/17/26 18:22, Lorenzo Stoakes (ARM) wrote: > Rather than referring to VMA flags with uncertain meaning, add a new > predicate that explicitly describes what possession of the VMA_PFNMAP_BIT > or VMA_MIXEDMAP_BIT flags mean, and then refer to that function for > determining VMA mergeability. > > Either flag means the contents of the mapping are owned by the kernel, > usually a driver, rather than by the core mm: the memory may be MMIO, > kernel-allocated pages or even ordinary pages the driver maps itself, but > the core must not populate, reclaim, migrate, copy-on-write or merge the > range on its own initiative. > > We initially also include VMA_IO_BIT here, as by implication, these must be > kernel-owned. (mlock() also sets VMA_IO_BIT transiently on ordinary VMAs > while locking them, which is addressed later in this series.) > > However the intent is to in future remove this, as no mapping should be > marked as an I/O mapping without also being marked with VMA_PFNMAP_BIT. > > This forms the basis of further work intended to improve how we express VMA > properties such as this. > > Also update the VMA userland tests to reflect the change. > > No functional change intended. Of course I have to bitch about the naming :) Intuitively: kernel owned vs ... user owned? No, it's kernel owned vs core-mm owned. Which implies core-mm is not part of the kernel? Yes, this is confusing. ;) I assume you're coming from "map_kernel_pages*", but that's rather "kernel memory" and not "kernel owned". Usually we say "driver owned" when not talking about pagecache/anon. Or user vs. kernel memory. So is it really all about "is this (excluding CoW) no ordinary user memory that we would track through the rmap" ? > > Signed-off-by: Lorenzo Stoakes (ARM) > --- > include/linux/mm.h | 56 ++++++++++++++++++++++++++++++++++++++++- > tools/testing/vma/include/dup.h | 29 ++++++++++++++++++++- > 2 files changed, 83 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 2a92193ac6a5..cab29d6e15c1 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1612,6 +1612,44 @@ static inline bool vma_is_shared_maywrite(const struct vm_area_struct *vma) > return is_shared_maywrite(&vma->flags); > } > > +/** > + * vma_flags_is_kernel_owned() - Do the specified VMA flags indicate that the > + * contents of the VMA are owned by the kernel rather than the core mm? > + * @flags: The VMA flags to test. > + * > + * A kernel-owned mapping is one whose contents are established and controlled > + * by the kernel, typically a driver, rather than by the core mm's fault and > + * rmap machinery. > + * > + * The mapping may be memory-mapped I/O, kernel-allocated pages or ordinary > + * pages the owner has chosen to map itself (shmem via a PFN map, for instance). > + * > + * In all cases the core mm must not populate, reclaim, migrate, copy-on-write > + * or merge it of its own accord. > + * > + * Pages mapped this way are not necessarily reference counted or map counted. > + * > + * Returns: true if the flags indicate a kernel-owned mapping. > + */ > +static inline bool vma_flags_is_kernel_owned(const vma_flags_t *flags) > +{ > + return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT, > + VMA_IO_BIT); I thought we have cases where we drivers insert pages and neither set VMA_PFNMAP_BIT nor VMA_MIXEDMAP_BIT. I assume vmf_insert_page_mkwrite() is fine because it is DAX doing it (should we limit this interface to DAX?). -- Cheers, David