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b=qZVXYvqUVMAUSYIwLAk/cf3Wu9vMlZicQ6LPzFPuA9V/7EpX5AL9sGet580dOCPom ihDG0C0ROWQLZ1SbhAMn/JFLDf119UKmA3N6MLgIZ49ijOVl0YMAoXAtkPEkx2xLCj Bs0jfRkyyFJmqxUmmInMf6yjah4js0nnZBRyLfT4iJDkdslrcAZJKRnfFRzcNw6NwX uz0Wt8++Kt1+mjG7pbeCi94DuNuTKkeN65M69JqO6r03joQLfyXNKlrrs0jiL9IyhA cvoPltyeWbvFPIJdUZXxrpdRyNzh/CvemjMQrbCFmL8puUHydjrWZ04VtSvNCdhkxl 2KqNkxFEMnluw== Message-ID: Date: Wed, 11 Feb 2026 10:28:28 +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, Fangrui Song 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-Stat-Signature: xrt38z1upcdgjuhxw8iowqibprkj7epe X-Rspamd-Queue-Id: 7928E4000B X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1770802117-158564 X-HE-Meta: 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 ga9Em32K Hazd40Ee5XXC6lbn52CVnczpYX5jOndLRuh+4qmqDQul37m++QiHfpnxem4SApqWXVodJ+gb3rAyX9IGyGO2P/tmlG+QTiNXFbwLKOyL3HQu7norThcPgTCEi1rSmd1XvkMEbDa4792OphtpkxTdci3t5dqbwSxdIVRVpLqkCkuIcm3TH9S9XgpC9l626GQ5bqXY/rp3qTjvwbWMnxoIY4zn+qt4n/qQy1xR1ccKKL+QJRYeK4tHzmpA3BGaiZxeCivnTJgowdgouaKIBzDi+m9loHHdxTtmWXpR42+o1lVbhY6Iri3tr9v0XxNFtgPQ4X7wKTZToV7Sdq4P7K9KxxucZBIEGyCFlgxIXjvLJIaMRKRofFku/sPgGfz3gGffHeEZk48hCTM6+ToT9L0qTXFmgfk0K4RIo9sT0BF6zQyOJ8u0= 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 00:00, Ackerley Tng wrote: > "David Hildenbrand (Arm)" writes: > >>> >>> 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. >> > > 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. Are you sure? We check for CONFIG_READ_ONLY_THP_FOR_FS before that: /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && (vm_flags & VM_EXEC)) { struct inode *inode = vma->vm_file->f_inode; return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } So if you have VM_EXEC on the VMA (mmaped with PROT_EXEC), it would work. I think secretmem sets SB_I_NOEXEC, which prevents that. Same for guest_memfd. v6.6.123 still has that VM_EXEC check in file_thp_enabled(). The check was dropped in commit: commit 7fbb5e188248c50f737720825da1864ce42536d1 Author: Fangrui Song Date: Tue Dec 19 21:41:23 2023 -0800 mm: remove VM_EXEC requirement for THP eligibility Commit e6be37b2e7bd ("mm/huge_memory.c: add missing read-only THP checking in transparent_hugepage_enabled()") introduced the VM_EXEC requirement, which is not strictly needed. lld's default --rosegment option and GNU ld's -z separate-code option (default on Linux/x86 since binutils 2.31) create a read-only PT_LOAD segment without the PF_X flag, which should be eligible for THP. So that one broke secretmem. So when we fix it, we should Fixes: 7fbb5e188248 ("mm: remove VM_EXEC requirement for THP eligibility") What about the following: diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 44ff8a648afd..9fbe5c28a6bc 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -94,6 +94,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) inode = file_inode(vma->vm_file); + if (IS_ANON_FILE(inode)) + return false; + return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } -- Cheers, David