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 D216D33D4E4 for ; Tue, 10 Feb 2026 09:33:14 +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=1770715994; cv=none; b=LfWN5mjMUBB+et3cwYFJSwIxpRyHDMwikMp7r/K5rRfJI8NyxSCLZxJ27UhrRrVBvUlt7kpE0pCharCMgcwZ4f3yDLCOAvbO0OeApBGwdWIHBY0D2gedrMPcaMp875KQZWI2iB1AQe9Q3ojHWzsSEkqdXaREKyrY8MuCAr8XUPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770715994; c=relaxed/simple; bh=BgcKV7dHeHVbm20HV3VLA5plyusJ9ZbXOgJvxKDGDeI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Cktj6xwfKG/D6r7GOJTTi5E8mR7rdbf7aHBxtH0MIvlHs7qkJ6R0trMRAVHoV/7riS9oCvtgfOKcFxhOuUQZXj3KHHXIyxvztxgx8eR4BAgGYKTpOezGF8lJ7W5ysq4KuM6nfIugyal+RdsLCiv7N9cq4H7eHbqvognc67BJBWY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lVWeB8fb; 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="lVWeB8fb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFF90C116C6; Tue, 10 Feb 2026 09:33:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770715994; bh=BgcKV7dHeHVbm20HV3VLA5plyusJ9ZbXOgJvxKDGDeI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=lVWeB8fbPSQmk5ZnZjfxYmqJ5aSP0JS3vYx0Vqq74YYPmMlYbtoJrGFZDnc1/x2LW eWPYxgha49wLuGMjUawePYF21z0O7tARazj+R23XvBeiIxqu5/08V8WNHwlXfIBbW4 Q/Y5ItJaRyFpZCHp/TgKRLWclZCDLA7jknQSUFb0t1x5Vp1w0zC45URa/kOvi+Gtgl VROBoaqKpS67RBMIRO0QJNxVBZdxYHmGF4SUXfmTOHXEQekBj3WKz2HRZra79+AO+5 yIHLpZcxzuFGhCdMLZcj+n3/cUaSRsU/T6I1p5PfHrUeaTAT30hJ246g723Ly2zprh STeJCP5RYZSoQ== Message-ID: Date: Tue, 10 Feb 2026 10:33:06 +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> 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 >> BUT, something just occurred to me. >> >> We added the mc-handling in >> >> commit 98c76c9f1ef7599b39bfd4bd99b8a760d4a8cd3b >> Author: Jiaqi Yan >> Date: Wed Mar 29 08:11:19 2023 -0700 >> >> mm/khugepaged: recover from poisoned anonymous memory >> >> .. >> >> So I assume kernels before that would crash when collapsing? >> >> Looking at 5.15.199, it does not contain 98c76c9f1e [1]. >> >> So I suspect we need a fix+stable backport. >> >> Who volunteers to try a secretmem reproducer on a stable kernel? :) >> > > 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. > >> >> The following is a bit nasty as well but should do the trick until we rip >> out the CONFIG_READ_ONLY_THP_FOR_FS stuff. >> >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 03886d4ccecc..4ac1cb36b861 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -40,6 +40,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include "internal.h" >> @@ -94,6 +95,10 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) >> >> inode = file_inode(vma->vm_file); >> >> + if (mapping_inaccessible(inode->i_mapping) || >> + secretmem_mapping(inode->i_mapping)) >> + return false; >> + > > Regarding the degradation of filesystems that don't support large folios > yet: Do you mean having the collapse function respect AS_FOLIO_ORDER_MAX > would disable collapsing for filesystems that actually want pages to be > collapsed, but don't update max folio order and hence appear to not > support large folios yet? > > What about a check like this instead > > if (!mapping_large_folio_support()) > return false; That would essentially disable CONFIG_READ_ONLY_THP_FOR_FS (support for THP before filesystems started supporting large folios officially), no? -- Cheers, David