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b=BMaLRZBSoyJej9h8rFbWett7fI7DOWV01JMoluJ9BEXoEd5AIF4J7k9wct136eI9U zk9Bc6kwY3f0KkRVUwzu5DdBtmEg1chlAnqZYJSHxBQLpnca04PdXtNGANKu8r2eU/ hpcipX0X6sYrojfkh3i3oaPQePjYXTmXnKcNv6BeNI1CfHVQlzq5XOGjZ0IvN3MRjz th9ztcw5lWynGDAHr6IlsolYXGVF1pL78gR7EFWjjynsdV44InfyEoyHSs+XfyLtFt GTEVICd9mm7h0JuFjfLSTrlmtRV/QgpT8oA5si0ejdsnJ5txVNRD/54hrc3NLVJu1L qpWP78YC4CEZQ== Message-ID: <5759bfba-f235-4b2d-bb30-919dcdfe7b2c@kernel.org> Date: Wed, 11 Feb 2026 10:29:40 +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() 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 X-Rspamd-Server: rspam12 X-Stat-Signature: xph9f3ya95rkdbsok9w69d5e1smyw3o6 X-Rspamd-Queue-Id: 2B1C68000B X-Rspam-User: X-HE-Tag: 1770802188-81084 X-HE-Meta: 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 56rd91Va CwBuy6bI8JGezBQz+9c/J0ErcqJEwHs0m6UD92l2701k/xTZPwMpJM35TyUn4qa4I4BXs3deDHJRYrEpIIdXJynL1Ioy82S3fSLecAL438e5tAQCLHCI69LOANtyUUfduGml8Mt/IQ+GDIOGl76ggeSAchl295MKX6KtgghaOGv4CRN71HiFUxs4CZR3j1s/wrC30RfVD0cwRGgNUbspBBIXnfHsKr1tZAJuX93NrvGeNrFQZuXaQynMI0wRqug+3BNTew8AWXpr4lhax33Rr6JuJO3Nt6lxAdD8pnQCndA2toHnbGgGqDZqrDR3Q707IwEWXQpW47S/1Sw/G3gmnzViFHGyAbVWmQvWl01OzvwQrbU1qWE98MSa1euzff++VRev9dGqhJlBjDtNKsXeTXgSse3CsxcZE0TFOk974Wt/7sq+gkm/Oy7KbAyQNDO65Ltrg 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 01:58, Ackerley Tng wrote: > Ackerley Tng writes: > >> "David Hildenbrand (Arm)" writes: >> >>> >>> 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. >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/khugepaged.c?h=v5.15.199#n469 >> > > 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. -- Cheers, David