From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Ackerley Tng <ackerleytng@google.com>,
Deepanshu Kartikey <kartikey406@gmail.com>
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
Subject: Re: [PATCH] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled()
Date: Wed, 11 Feb 2026 17:44:34 +0100 [thread overview]
Message-ID: <8a186f0f-c192-4e89-a11f-705c78d52233@kernel.org> (raw)
In-Reply-To: <3932d6b3-5de9-4c84-b60a-f2a8cc2457e2@kernel.org>
On 2/11/26 17:35, David Hildenbrand (Arm) wrote:
> On 2/11/26 17:16, Ackerley Tng wrote:
>> "David Hildenbrand (Arm)" <david@kernel.org> writes:
>>
>>>
>>>
>>> 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.
>
Ah, but that might still fail, because we can identify the page as such.
Hm ... we'd need some introspection interface indeed.
--
Cheers,
David
next prev parent reply other threads:[~2026-02-11 16:44 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 3:35 Deepanshu Kartikey
2026-02-09 10:24 ` David Hildenbrand (Arm)
2026-02-09 10:41 ` David Hildenbrand (Arm)
2026-02-09 13:06 ` Deepanshu Kartikey
2026-02-09 18:22 ` Ackerley Tng
2026-02-09 19:45 ` David Hildenbrand (Arm)
2026-02-09 20:13 ` David Hildenbrand (Arm)
2026-02-09 21:31 ` Ackerley Tng
2026-02-10 9:33 ` David Hildenbrand (Arm)
2026-02-10 23:00 ` Ackerley Tng
2026-02-11 0:58 ` Ackerley Tng
2026-02-11 2:01 ` Deepanshu Kartikey
2026-02-11 9:29 ` David Hildenbrand (Arm)
2026-02-11 16:16 ` Ackerley Tng
2026-02-11 16:35 ` David Hildenbrand (Arm)
2026-02-11 16:44 ` David Hildenbrand (Arm) [this message]
2026-02-11 1:59 ` Deepanshu Kartikey
2026-02-11 9:28 ` David Hildenbrand (Arm)
2026-02-11 14:50 ` Deepanshu Kartikey
2026-02-11 15:38 ` Ackerley Tng
2026-02-11 16:45 ` David Hildenbrand (Arm)
2026-02-12 22:19 ` Ackerley Tng
2026-02-13 5:02 ` Deepanshu Kartikey
2026-02-13 9:06 ` David Hildenbrand (Arm)
2026-02-21 4:37 ` Deepanshu Kartikey
2026-02-10 1:51 ` Deepanshu Kartikey
2026-02-10 9:33 ` David Hildenbrand (Arm)
2026-02-09 23:37 ` kernel test robot
2026-02-10 17:51 ` kernel test robot
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