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bh=N8Q2YI+aHkKmnXGsLGvl2FTJOOn9qfXrIl8SfLUQfBY=; b=n2TBblyfC5mElmDPs+crnf/DUwpkjQzov5fr23ovc2IQmKk24MCXF3UqY3iIkYjy7Z7bUm H7ZtvC01i3D0GdYXxByMcVx7g3xpJ1TCbVUgEy3LarUuAi9J0niNcCGhqQxr9fuHFa9Y5h HU4yjTCM1hCL+DeW7JZ2FYnZlm2TrVE= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=hRTaRylF; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id D081E4089A; Mon, 23 Mar 2026 17:52:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D040BC4CEF7; Mon, 23 Mar 2026 17:51:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774288320; bh=5hK0lEzqKpD6B7ugeP6Y6wm+od5B652rwYVrsebBxYw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hRTaRylFaKiULg4U5aE4ktkU7BRuQLdv1usSIlvOyM3oyxczdRVbPv+Pr3eENuc0B eNT73uQH0QPu3oY+IbPuS1dvOyK2mZihmZ0UpnDjsoN8FJqzyWvG2A0tXjGZiG317m tbP8sYYAGc0NkxOd7poaHGmvnhf8U6+WFBQ85I1eRmcmFu4ftMRKHaF8L7SIv5/s8c ZF/oYLz912UjohFG0YBksMiYmu4/SHJUsawsDt9nBkWWWBO4KkprZa8ALqadxd81RG BgvMsAmxJ9MvZD3XqCHx4Uwwxf7Zu0a7PHi6AjCOgSDlC4eZ5n/FpnMXZI9VnY0H39 pINsESfKgcnZg== Message-ID: <54f9b5a7-b8a9-486a-9c12-a910f5287947@kernel.org> Date: Mon, 23 Mar 2026 18:51:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 02/16] set_memory: add folio_{zap,restore}_direct_map helpers To: "Kalyazin, Nikita" , "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kernel@xen0n.name" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "loongarch@lists.linux.dev" , "linux-pm@vger.kernel.org" Cc: "pbonzini@redhat.com" , "corbet@lwn.net" , "maz@kernel.org" , "oupton@kernel.org" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "seanjc@google.com" , "tglx@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "luto@kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "akpm@linux-foundation.org" , "lorenzo.stoakes@oracle.com" , "vbabka@kernel.org" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "martin.lau@linux.dev" , "eddyz87@gmail.com" , "song@kernel.org" , "yonghong.song@linux.dev" , "john.fastabend@gmail.com" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "haoluo@google.com" , "jolsa@kernel.org" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "skhan@linuxfoundation.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "kevin.brodsky@arm.com" , "ackerleytng@google.com" , "yosry@kernel.org" , "ajones@ventanamicro.com" , "maobibo@loongson.cn" , "tabba@google.com" , "prsampat@amd.com" , "wu.fei9@sanechips.com.cn" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "aou@eecs.berkeley.edu" , "borntraeger@linux.ibm.com" , "chenhuacai@kernel.org" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "hca@linux.ibm.com" , "palmer@dabbelt.com" , "pjw@kernel.org" , "shijie@os.amperecomputing.com" , "svens@linux.ibm.com" , "thuth@redhat.com" , "wyihan@google.com" , "yang@os.amperecomputing.com" , "Jonathan.Cameron@huawei.com" , "Liam.Howlett@oracle.com" , "urezki@gmail.com" , "zhengqi.arch@bytedance.com" , "gerald.schaefer@linux.ibm.com" , "jiayuan.chen@shopee.com" , "lenb@kernel.org" , "osalvador@suse.de" , "pavel@kernel.org" , "rafael@kernel.org" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" References: <20260317141031.514-1-kalyazin@amazon.com> <20260317141031.514-3-kalyazin@amazon.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260317141031.514-3-kalyazin@amazon.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 6B03C4000B X-Stat-Signature: uji9983cziorj584puf4rk36tkoefyc6 X-HE-Tag: 1774288322-361652 X-HE-Meta: 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 gridSQV9 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/17/26 15:10, Kalyazin, Nikita wrote: > From: Nikita Kalyazin > > Let's provide folio_{zap,restore}_direct_map helpers as preparation for > supporting removal of the direct map for guest_memfd folios. > In folio_zap_direct_map(), flush TLB to make sure the data is not > accessible. > > The new helpers need to be accessible to KVM on architectures that > support guest_memfd (x86 and arm64). > > Direct map removal gives guest_memfd the same protection that > memfd_secret does, such as hardening against Spectre-like attacks > through in-kernel gadgets. Maybe mention that there might be a double TLB flush on some architectures, but that that is something to figure out later. Same behavior in secretmem code where this will be used next. > > Signed-off-by: Nikita Kalyazin > --- > include/linux/set_memory.h | 13 ++++++++++++ > mm/memory.c | 42 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 55 insertions(+) > > diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h > index 1a2563f525fc..24caea2931f9 100644 > --- a/include/linux/set_memory.h > +++ b/include/linux/set_memory.h > @@ -41,6 +41,15 @@ static inline int set_direct_map_valid_noflush(const void *addr, > return 0; > } > > +static inline int folio_zap_direct_map(struct folio *folio) > +{ > + return 0; Should we return -ENOSYS here or similar? > +} > + > +static inline void folio_restore_direct_map(struct folio *folio) > +{ > +} > + > static inline bool kernel_page_present(struct page *page) > { > return true; > @@ -57,6 +66,10 @@ static inline bool can_set_direct_map(void) > } > #define can_set_direct_map can_set_direct_map > #endif > + > +int folio_zap_direct_map(struct folio *folio); > +void folio_restore_direct_map(struct folio *folio); > + > #endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */ > > #ifdef CONFIG_X86_64 > diff --git a/mm/memory.c b/mm/memory.c > index 07778814b4a8..cab6bb237fc0 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -78,6 +78,7 @@ > #include > #include > #include > +#include > > #include > > @@ -7478,3 +7479,44 @@ void vma_pgtable_walk_end(struct vm_area_struct *vma) > if (is_vm_hugetlb_page(vma)) > hugetlb_vma_unlock_read(vma); > } > + > +#ifdef CONFIG_ARCH_HAS_SET_DIRECT_MAP > +/** > + * folio_zap_direct_map - remove a folio from the kernel direct map > + * @folio: folio to remove from the direct map > + * > + * Removes the folio from the kernel direct map and flushes the TLB. This may > + * require splitting huge pages in the direct map, which can fail due to memory > + * allocation. Best to mention "So far, only order-0 folios are supported." and then ... > + * > + * Return: 0 on success, or a negative error code on failure. > + */ > +int folio_zap_direct_map(struct folio *folio) > +{ > + const void *addr = folio_address(folio); > + int ret; > + if (folio_test_large(folio)) return -EINVAL; With that, Acked-by: David Hildenbrand (Arm) -- Cheers, David