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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770827749; bh=0kUjF1LFpJENQZHt7Fo59M51dgtOhJPv1ymb5k5n9ns=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SzkyrmethJfMNPOML4ad9CVXaNQugmMiRG8PaJsHrIcOkqX1YtAk3fKac+786QRf4 vzpBWFyheBjkmS1rup9jVW4lV8AgVCH0cPYcd4hJrDDSRWA6KPVKWI3uUUnrs/cwAE fz0GjhdZMOrWKNmJdZGhX4Gp9jprqAiumUgM+Yo9c/PPAXP9up/+fFZqI6bYfbc9xL rvLmKpk4vqLo967ptfMgD0y+AsXhoqb0umQ6S4h+7YmLGbMERGK0aw0Mvu8jZak5Hk Hd0kRSZqtdiMJTmZC7RLxAy/CXEVwGjJGd++2F3CphCly9mLmk4Mmt6xYsQQF7ecCI 6NmRlnTr6l4Ww== Message-ID: <3932d6b3-5de9-4c84-b60a-f2a8cc2457e2@kernel.org> Date: Wed, 11 Feb 2026 17:35:40 +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> <5759bfba-f235-4b2d-bb30-919dcdfe7b2c@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-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 673EC1C0011 X-Stat-Signature: jj4re3j633krtiaz69h597b56rfyi5nr X-HE-Tag: 1770827750-919859 X-HE-Meta: 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 MZG5eca4 En/PTDAEdmDjGtkana3YLFXE/3lVrO3Wmj78dMtbfwFwQtp5kk02IaCCudNFLby49XCQ1NWbd00QexhJBchtTsqgTQP+6Pm6yL9siDXkXRrsNvvlrHOIe8p3NLaXaL2CG+nFfw2AREbecj5CyDCzF0zi4KviB3WnHcbTXxNkpovMuzQhoAkMsX7nSkx1NIPGnWfOCjd4+vwEJ05F/b8/k9WnVyOJxCNoOxDC7nxfw6jOg7ttxGasabMqVlt8gl4m0GZZPg6m48IJLXwWkQTD3URgjV0Ohsq87NfApbdPsZpWeMCCLsA0MR31p/HBNRGryu7AhKTGC/KIoaGMuqkYl3rWup3hxfxbcHj5SZ3bEsC1fF+mDwF6KtubdMonrNKl/lk9Xsl8euJZ0PU9QYc0PQ9s13G6tQC6ehysSy0F6YVlpE9Ow9XtLTKAeEz9qdBEeU0za 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 17:16, Ackerley Tng wrote: > "David Hildenbrand (Arm)" writes: > >> On 2/11/26 01:58, Ackerley Tng wrote: >>> Ackerley Tng writes: >>> >>> >>> 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. >> > > 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. -- Cheers, David