From nobody Thu Apr 2 11:55:34 2026 Received: from fra-out-010.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-010.esa.eu-central-1.outbound.mail-perimeter.amazon.com [63.178.143.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0AD523E315E; Tue, 17 Mar 2026 14:10:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=63.178.143.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773756661; cv=none; b=juyfu7oouLpB8DsHeYXB4wXZJbEEv03PsfryyDYlAIHDkaLzX4kPCUf7kydK0An84ikw5SlgC2JXeA5MIssCa2isy7OwI3dx/2sRzBq0VPOwTZhlgH7M/9GnVUvGSKp+KWU2vvHbRH9s8PaBOa0ut9j8qWYzotxcIU9PuFemW64= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773756661; c=relaxed/simple; bh=QEElU4I6Wx3gLFCLNkYzTvhso8sHIeR5dGXiMkdWM5M=; h=From:To:CC:Subject:Date:Message-ID:References:In-Reply-To: Content-Type:MIME-Version; b=QkMpvAfqrHWCgIcvlMNCYpuPtcPYIhZBVK4WfWCMITJVKD/gxrBF66QYKHlbmjN4HpULFUOSyx5pCmVgT40yvxumsu3S+EpX5Oqi6+a4kHzPZ4iTYzEYmvex8Sgj0xBE8rF/9OpJY+JcV0WIt59IlbTXe/lkuOZeJNUcYXOmHrE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b=UMNE0E74; arc=none smtp.client-ip=63.178.143.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b="UMNE0E74" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.uk; i=@amazon.co.uk; q=dns/txt; s=amazoncorp2; t=1773756660; x=1805292660; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=VYvr0CwhFQIS2ZaS+F5r9gx/5JKbQ+VxsBq0F/u29+4=; b=UMNE0E74JIs9Nq2LHTbUB96xBBX6evc52P78WoBVpXZ7NFlGWEZeXfDF h+1glKaf1y/Bs0v7LiDXz311iSJLGUmFfBHXmLW151iAbUMB4L6d0d21v TOLVLyga30kiXMnilni8pXmfFFzIY8A0bUp0XKAkYJoeTCN5AHGI7/OIB VRHUTNGyUZKRID0NL9mG/ZZQd/v04GMaFjnCxZtZJC5DcZsZjjUcOPjgM drsrl3Ah7cAHdwwnkcX5K78akQ7epJhT8eMea1LZ2eZE2lq7052KgZVex VKVLsExjZWaopRbVcGIcnePKrfTAh/U9SZ7Mwy/BrUlagxFmHUgxWsIs4 w==; X-CSE-ConnectionGUID: qXHvxhvLTNeyghAyahceNg== X-CSE-MsgGUID: puQ8nFyqTDmGaW3b5uM8dg== X-IronPort-AV: E=Sophos;i="6.23,124,1770595200"; d="scan'208";a="10894914" Received: from ip-10-6-11-83.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.11.83]) by internal-fra-out-010.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2026 14:10:57 +0000 Received: from EX19MTAEUC001.ant.amazon.com [54.240.197.225:28985] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.12.108:2525] with esmtp (Farcaster) id d8fc662a-bddf-4bdd-a07a-65c8795e29a8; Tue, 17 Mar 2026 14:10:56 +0000 (UTC) X-Farcaster-Flow-ID: d8fc662a-bddf-4bdd-a07a-65c8795e29a8 Received: from EX19D005EUB002.ant.amazon.com (10.252.51.103) by EX19MTAEUC001.ant.amazon.com (10.252.51.193) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.37; Tue, 17 Mar 2026 14:10:56 +0000 Received: from EX19D005EUB003.ant.amazon.com (10.252.51.31) by EX19D005EUB002.ant.amazon.com (10.252.51.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.37; Tue, 17 Mar 2026 14:10:55 +0000 Received: from EX19D005EUB003.ant.amazon.com ([fe80::b825:becb:4b38:da0c]) by EX19D005EUB003.ant.amazon.com ([fe80::b825:becb:4b38:da0c%3]) with mapi id 15.02.2562.037; Tue, 17 Mar 2026 14:10:55 +0000 From: "Kalyazin, Nikita" To: "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" , "david@kernel.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" , "Kalyazin, Nikita" Subject: [PATCH v11 02/16] set_memory: add folio_{zap,restore}_direct_map helpers Thread-Topic: [PATCH v11 02/16] set_memory: add folio_{zap,restore}_direct_map helpers Thread-Index: AQHcthfeEMFcBldU0EKH3aXM8Uk9Xg== Date: Tue, 17 Mar 2026 14:10:55 +0000 Message-ID: <20260317141031.514-3-kalyazin@amazon.com> References: <20260317141031.514-1-kalyazin@amazon.com> In-Reply-To: <20260317141031.514-1-kalyazin@amazon.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Nikita Kalyazin Acked-by: David Hildenbrand (Arm) Reviewed-by: Ackerley Tng --- 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 voi= d *addr, return 0; } =20 +static inline int folio_zap_direct_map(struct folio *folio) +{ + return 0; +} + +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 */ =20 #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 =20 #include =20 @@ -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 m= emory + * allocation. + * + * Return: 0 on success, or a negative error code on failure. + */ +int folio_zap_direct_map(struct folio *folio) +{ + const void *addr =3D folio_address(folio); + int ret; + + ret =3D set_direct_map_valid_noflush(addr, folio_nr_pages(folio), false); + flush_tlb_kernel_range((unsigned long)addr, + (unsigned long)addr + folio_size(folio)); + + return ret; +} +EXPORT_SYMBOL_FOR_MODULES(folio_zap_direct_map, "kvm"); + +/** + * folio_restore_direct_map - restore the kernel direct map entry for a fo= lio + * @folio: folio whose direct map entry is to be restored + * + * This may only be called after a prior successful folio_zap_direct_map()= on + * the same folio. Because the zap will have already split any huge pages= in + * the direct map, restoration here only updates protection bits and cannot + * fail. + */ +void folio_restore_direct_map(struct folio *folio) +{ + WARN_ON_ONCE(set_direct_map_valid_noflush(folio_address(folio), + folio_nr_pages(folio), true)); +} +EXPORT_SYMBOL_FOR_MODULES(folio_restore_direct_map, "kvm"); +#endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */ --=20 2.50.1