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 8A3DA3557E9 for ; Wed, 11 Feb 2026 09:28:36 +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=1770802116; cv=none; b=DRXSRNStQz3GVdH4myslMcLjDkaSiNJoZt/ntByf9RjUY5JkDmHxpEtEZL2+r73MBnxbsNbZF+Mp4GT2TH2GA8/ezOFoKFqRacjYiBHRc4pnsECWfZyeC9Gat4u9+XWoJaNXkO0/+tN2gNTKqw/LbQ72ZG/cyefuT6XKkp6F4eQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770802116; c=relaxed/simple; bh=pOY9HpZc4cB550PofSf69VKd4oFcGg+ZGQ9glPc/n7w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rpL2sIxJnEZbx282hvKe3FtQUOxOqMI0bExpdGbVToxOOoO0hiI4Ik7gPthvUKZR+2SANOoevwIkdBDm2DgyC08pTxoD3d6TiUVSnesffhprbAoOUSAQuURvsH2GZL5HmrikEtQP9oiW9dW/i7tXC+4Mg0jHEre9gtTwn5OWzko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qZVXYvqU; 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="qZVXYvqU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9EB15C4CEF7; Wed, 11 Feb 2026 09:28:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770802116; bh=pOY9HpZc4cB550PofSf69VKd4oFcGg+ZGQ9glPc/n7w=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qZVXYvqUVMAUSYIwLAk/cf3Wu9vMlZicQ6LPzFPuA9V/7EpX5AL9sGet580dOCPom ihDG0C0ROWQLZ1SbhAMn/JFLDf119UKmA3N6MLgIZ49ijOVl0YMAoXAtkPEkx2xLCj Bs0jfRkyyFJmqxUmmInMf6yjah4js0nnZBRyLfT4iJDkdslrcAZJKRnfFRzcNw6NwX uz0Wt8++Kt1+mjG7pbeCi94DuNuTKkeN65M69JqO6r03joQLfyXNKlrrs0jiL9IyhA cvoPltyeWbvFPIJdUZXxrpdRyNzh/CvemjMQrbCFmL8puUHydjrWZ04VtSvNCdhkxl 2KqNkxFEMnluw== Message-ID: Date: Wed, 11 Feb 2026 10:28:28 +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, Fangrui Song 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> 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 00:00, Ackerley Tng wrote: > "David Hildenbrand (Arm)" writes: > >>> >>> I could give this a shot. 5.15.199 doesn't have AS_INACCESSIBLE. Should >>> we backport AS_INACCESSIBLE there or could the fix for 5.15.199 just be >>> special-casing secretmem like you suggested below? >> >> Yes. If there is no guest_memfd we wouldn't need it. >> > > Seems like on 5.15.199 there's a hugepage_vma_check(), which will return > false since secretmem has vma->vm_ops defined [1], so secretmem VMAs are > skipped. Are you sure? We check for CONFIG_READ_ONLY_THP_FOR_FS before that: /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && (vm_flags & VM_EXEC)) { struct inode *inode = vma->vm_file->f_inode; return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } So if you have VM_EXEC on the VMA (mmaped with PROT_EXEC), it would work. I think secretmem sets SB_I_NOEXEC, which prevents that. Same for guest_memfd. v6.6.123 still has that VM_EXEC check in file_thp_enabled(). The check was dropped in commit: commit 7fbb5e188248c50f737720825da1864ce42536d1 Author: Fangrui Song Date: Tue Dec 19 21:41:23 2023 -0800 mm: remove VM_EXEC requirement for THP eligibility Commit e6be37b2e7bd ("mm/huge_memory.c: add missing read-only THP checking in transparent_hugepage_enabled()") introduced the VM_EXEC requirement, which is not strictly needed. lld's default --rosegment option and GNU ld's -z separate-code option (default on Linux/x86 since binutils 2.31) create a read-only PT_LOAD segment without the PF_X flag, which should be eligible for THP. So that one broke secretmem. So when we fix it, we should Fixes: 7fbb5e188248 ("mm: remove VM_EXEC requirement for THP eligibility") What about the following: diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 44ff8a648afd..9fbe5c28a6bc 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -94,6 +94,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) inode = file_inode(vma->vm_file); + if (IS_ANON_FILE(inode)) + return false; + return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } -- Cheers, David