From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DADBD343D80 for ; Wed, 11 Feb 2026 16:35:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770827750; cv=none; b=pUq3W6Y/tM/UiVh76UzPS9S23bskwoFk1hCNCuXiiyE4K9WsLlk/OQIUGzDNBGsAxgoVyqfOcT5naZZDbIZsFTjd6iFmreveSXuOxCJwKBiFNlUX3rFT5TptbfapP/l1Vh4ZRVlG95U5ue2c+ctf+N6EyvF7Fy7ClvWDhMUC4Xc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770827750; c=relaxed/simple; bh=0kUjF1LFpJENQZHt7Fo59M51dgtOhJPv1ymb5k5n9ns=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NpQc/4KJDV1RMisW9EUwS+Qb9Q81lTyHDxmpdGV76f2oggkaeqDjFI69zy+cPC/dBKXaSyEZcrnlaBMaAtCsuvFoSqi2fkiBJTUwVYhUIJ3rFTA+WvTZgZtgRef4jCkx4odN38hXKh/jsUuxWSd1rbJ4m03xK2pNr7hF65uo+Co= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Szkyrmet; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Szkyrmet" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B0CEC4CEF7; Wed, 11 Feb 2026 16:35:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770827749; bh=0kUjF1LFpJENQZHt7Fo59M51dgtOhJPv1ymb5k5n9ns=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SzkyrmethJfMNPOML4ad9CVXaNQugmMiRG8PaJsHrIcOkqX1YtAk3fKac+786QRf4 vzpBWFyheBjkmS1rup9jVW4lV8AgVCH0cPYcd4hJrDDSRWA6KPVKWI3uUUnrs/cwAE fz0GjhdZMOrWKNmJdZGhX4Gp9jprqAiumUgM+Yo9c/PPAXP9up/+fFZqI6bYfbc9xL rvLmKpk4vqLo967ptfMgD0y+AsXhoqb0umQ6S4h+7YmLGbMERGK0aw0Mvu8jZak5Hk Hd0kRSZqtdiMJTmZC7RLxAy/CXEVwGjJGd++2F3CphCly9mLmk4Mmt6xYsQQF7ecCI 6NmRlnTr6l4Ww== Message-ID: <3932d6b3-5de9-4c84-b60a-f2a8cc2457e2@kernel.org> Date: Wed, 11 Feb 2026 17:35:40 +0100 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] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled() To: Ackerley Tng , Deepanshu Kartikey Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, seanjc@google.com, pbonzini@redhat.com, michael.roth@amd.com, vannapurve@google.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com References: <20260209033558.22943-1-kartikey406@gmail.com> <0d9cada8-7148-4a5c-a09d-120ef54559d7@kernel.org> <4ed1b111-f2f1-4f89-9308-fdd9d706ca37@kernel.org> <8f188d73-fc97-414b-bdaa-e72032b2bf82@kernel.org> <5759bfba-f235-4b2d-bb30-919dcdfe7b2c@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/11/26 17:16, Ackerley Tng wrote: > "David Hildenbrand (Arm)" writes: > >> On 2/11/26 01:58, Ackerley Tng wrote: >>> Ackerley Tng writes: >>> >>> >>> On 6.1.162, secretmem VMAs are skipped since secretmem VMAs are not >>> anonymous [2]. >>> >>> [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/huge_memory.c?h=v6.1.162#n135 >>> >>> Same for 6.6.123 [3]. >>> >>> [3] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/huge_memory.c?h=v6.6.123#n125 >>> >>> It breaks in 6.12.69 [4]. >> >> >> Do you have a reproducer? If so, which behavior does it trigger? >> >> I would assume that we would suddenly have secretmem pages (THP) that >> have a directmap. Or some page copy would crash the kernel. >> > > Is there a good way to verify from userspace that the directmap hasn't > been restored? Should I use CONFIG_PTDUMP_DEBUGFS? Anything that uses GUP must fail on that secretmem memory. Like doing an O_DIRECT read/write or using vmsplice. -- Cheers, David