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b=mOFAT6+9r1pqOhNwJyH+QKiM+kKmqWwbpVUCw9nACztYjI3LjrfapKAbq9v0NzYlJ 99FrmI0VZ2i5nCI2BcC8zB0serNLSjVe2w9p/DnbA+brDwxiS47HdaEj4MAEEdhzMZ ytwpHrw3OVv2lgz8LhrFq1VR7BBsnsKP0sqX/9B+VWSyYVmL2LJVfnJXyyEWPYytq1 mBa2r65CDpnCL7fFZ7f4CaFzv77qo9a9eWArS0AiRjmCY/YrDhYEE0LKh6+W+wck3X GdoBvQH0lfs0hgoMHhLAwGvLJUmBKluUvSt4yDZDf8tMuNSLMF3BRM5Eqrp8PIkR5m UjG2oXgs2WTAQ== Message-ID: <8a186f0f-c192-4e89-a11f-705c78d52233@kernel.org> Date: Wed, 11 Feb 2026 17:44:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled() From: "David Hildenbrand (Arm)" 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> <3932d6b3-5de9-4c84-b60a-f2a8cc2457e2@kernel.org> Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 735EBC0002 X-Stat-Signature: dqfzrr5myt3swr6if8wy7r1uhje86knj X-Rspam-User: X-HE-Tag: 1770828283-127214 X-HE-Meta: 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 QhVC7F9M IxWfpRQdzVk3uZlvSwEjUu5i1WKACOv4BtjPeZ1saNxbaXLeQXXnCqbEGCyKKGNW+peMpqxCiAVVNB7fiHtZGI1skxng8oscjQB52d8CujbbATfTN2+7wssPzYIl1Kb1uk6HbVp33OIpsIjZt5vgzvr9Gfy+MCY233N7Ri7wQJwHPV+ONcU9fGkPylZG5zvVDSZayNqB4U/DNRcTf5IuslO8oQIryIvImYdTiUupvYTvgzDcka4rHKlTxi7e4XELqcvK482LybKpnO05+GiDKhXxg3MGjWNxYa1a1aX/Tl8LovcLYFZh4O+q2Y0vviLUX089mrWdB1DQdIvxzjDOwI5sHTDeIIf+7dSsj3fKmCIP7dbhYIy5/jo+E96kqQdxnoSAI7dl+etBRNGCRvQ1gToyttiZ+FPBhYhffgmWTLCsIcTodtmsAJ1sbhPKbybsO7EGR X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/11/26 17:35, David Hildenbrand (Arm) wrote: > On 2/11/26 17:16, Ackerley Tng wrote: >> "David Hildenbrand (Arm)" 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