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Thu, 15 Jan 2026 11:04:00 +0000 (UTC) X-Farcaster-Flow-ID: 78798bdf-4355-47da-99ae-a3a26432276e Received: from EX19D005EUB003.ant.amazon.com (10.252.51.31) by EX19MTAEUB002.ant.amazon.com (10.252.51.79) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Thu, 15 Jan 2026 11:04:00 +0000 Received: from [192.168.15.69] (10.106.82.11) by EX19D005EUB003.ant.amazon.com (10.252.51.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Thu, 15 Jan 2026 11:03:57 +0000 Message-ID: <373776f9-fe57-4374-8f8f-c43fdb193f19@amazon.com> Date: Thu, 15 Jan 2026 11:03:56 +0000 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Subject: Re: [PATCH v9 01/13] set_memory: add folio_{zap, restore}_direct_map helpers To: Huacai Chen , "Kalyazin, Nikita" CC: "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" , "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@linutronix.de" , "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" , "Liam.Howlett@oracle.com" , "vbabka@suse.cz" , "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" , "shuah@kernel.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" , "maobibo@loongson.cn" , "prsampat@amd.com" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "aou@eecs.berkeley.edu" , "borntraeger@linux.ibm.com" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "hca@linux.ibm.com" , "Jonathan.Cameron@huawei.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" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" References: <20260114134510.1835-1-kalyazin@amazon.com> <20260114134510.1835-2-kalyazin@amazon.com> Content-Language: en-US From: Nikita Kalyazin Autocrypt: addr=kalyazin@amazon.com; keydata= xjMEY+ZIvRYJKwYBBAHaRw8BAQdA9FwYskD/5BFmiiTgktstviS9svHeszG2JfIkUqjxf+/N JU5pa2l0YSBLYWx5YXppbiA8a2FseWF6aW5AYW1hem9uLmNvbT7CjwQTFggANxYhBGhhGDEy BjLQwD9FsK+SyiCpmmTzBQJnrNfABQkFps9DAhsDBAsJCAcFFQgJCgsFFgIDAQAACgkQr5LK IKmaZPOpfgD/exazh4C2Z8fNEz54YLJ6tuFEgQrVQPX6nQ/PfQi2+dwBAMGTpZcj9Z9NvSe1 CmmKYnYjhzGxzjBs8itSUvWIcMsFzjgEY+ZIvRIKKwYBBAGXVQEFAQEHQCqd7/nb2tb36vZt ubg1iBLCSDctMlKHsQTp7wCnEc4RAwEIB8J+BBgWCAAmFiEEaGEYMTIGMtDAP0Wwr5LKIKma ZPMFAmes18AFCQWmz0MCGwwACgkQr5LKIKmaZPNTlQEA+q+rGFn7273rOAg+rxPty0M8lJbT i2kGo8RmPPLu650A/1kWgz1AnenQUYzTAFnZrKSsXAw5WoHaDLBz9kiO5pAK In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: EX19D015EUA002.ant.amazon.com (10.252.50.219) To EX19D005EUB003.ant.amazon.com (10.252.51.31) On 15/01/2026 10:54, Huacai Chen wrote: > Hi, Nikita, Hi Huacai, > > On Wed, Jan 14, 2026 at 9:45 PM Kalyazin, Nikita wrote: >> >> From: Nikita Kalyazin >> >> These allow guest_memfd to remove its memory from the direct map. >> Only implement them for architectures that have direct map. >> In folio_zap_direct_map(), flush TLB on architectures where >> set_direct_map_valid_noflush() does not flush it internally. >> >> The new helpers need to be accessible to KVM on architectures that >> support guest_memfd (x86 and arm64). Since arm64 does not support >> building KVM as a module, only export them on x86. >> >> 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 >> --- >> arch/arm64/include/asm/set_memory.h | 2 ++ >> arch/arm64/mm/pageattr.c | 12 ++++++++++++ >> arch/loongarch/include/asm/set_memory.h | 2 ++ >> arch/loongarch/mm/pageattr.c | 16 ++++++++++++++++ >> arch/riscv/include/asm/set_memory.h | 2 ++ >> arch/riscv/mm/pageattr.c | 16 ++++++++++++++++ >> arch/s390/include/asm/set_memory.h | 2 ++ >> arch/s390/mm/pageattr.c | 18 ++++++++++++++++++ >> arch/x86/include/asm/set_memory.h | 2 ++ >> arch/x86/mm/pat/set_memory.c | 20 ++++++++++++++++++++ >> include/linux/set_memory.h | 10 ++++++++++ >> 11 files changed, 102 insertions(+) >> >> diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h >> index 90f61b17275e..d949f1deb701 100644 >> --- a/arch/arm64/include/asm/set_memory.h >> +++ b/arch/arm64/include/asm/set_memory.h >> @@ -14,6 +14,8 @@ int set_memory_valid(unsigned long addr, int numpages, int enable); >> int set_direct_map_invalid_noflush(struct page *page); >> int set_direct_map_default_noflush(struct page *page); >> int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); >> +int folio_zap_direct_map(struct folio *folio); >> +int folio_restore_direct_map(struct folio *folio); >> bool kernel_page_present(struct page *page); >> >> int set_memory_encrypted(unsigned long addr, int numpages); >> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c >> index f0e784b963e6..a94eff324dda 100644 >> --- a/arch/arm64/mm/pageattr.c >> +++ b/arch/arm64/mm/pageattr.c >> @@ -357,6 +357,18 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid) >> return set_memory_valid(addr, nr, valid); >> } >> >> +int folio_zap_direct_map(struct folio *folio) >> +{ >> + return set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), false); >> +} >> + >> +int folio_restore_direct_map(struct folio *folio) >> +{ >> + return set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), true); >> +} >> + >> #ifdef CONFIG_DEBUG_PAGEALLOC >> /* >> * This is - apart from the return value - doing the same >> diff --git a/arch/loongarch/include/asm/set_memory.h b/arch/loongarch/include/asm/set_memory.h >> index 55dfaefd02c8..9bc80ac420a9 100644 >> --- a/arch/loongarch/include/asm/set_memory.h >> +++ b/arch/loongarch/include/asm/set_memory.h >> @@ -18,5 +18,7 @@ bool kernel_page_present(struct page *page); >> int set_direct_map_default_noflush(struct page *page); >> int set_direct_map_invalid_noflush(struct page *page); >> int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); >> +int folio_zap_direct_map(struct folio *folio); >> +int folio_restore_direct_map(struct folio *folio); >> >> #endif /* _ASM_LOONGARCH_SET_MEMORY_H */ >> diff --git a/arch/loongarch/mm/pageattr.c b/arch/loongarch/mm/pageattr.c >> index f5e910b68229..14bd322dd112 100644 >> --- a/arch/loongarch/mm/pageattr.c >> +++ b/arch/loongarch/mm/pageattr.c >> @@ -236,3 +236,19 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid) >> >> return __set_memory(addr, 1, set, clear); >> } >> + >> +int folio_zap_direct_map(struct folio *folio) >> +{ >> + int ret; >> + >> + ret = set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), false); >> + >> + return ret; > Why not use a single statement which is the same as the ARM64 version? > The RISCV version has the same problem. No reason for them to be different. Will update in the next version. Thank you! > > Huacai > >> +} >> + >> +int folio_restore_direct_map(struct folio *folio) >> +{ >> + return set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), true); >> +} >> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h >> index 87389e93325a..16557b70c830 100644 >> --- a/arch/riscv/include/asm/set_memory.h >> +++ b/arch/riscv/include/asm/set_memory.h >> @@ -43,6 +43,8 @@ static inline int set_kernel_memory(char *startp, char *endp, >> int set_direct_map_invalid_noflush(struct page *page); >> int set_direct_map_default_noflush(struct page *page); >> int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); >> +int folio_zap_direct_map(struct folio *folio); >> +int folio_restore_direct_map(struct folio *folio); >> bool kernel_page_present(struct page *page); >> >> #endif /* __ASSEMBLER__ */ >> diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c >> index 3f76db3d2769..2c218868114b 100644 >> --- a/arch/riscv/mm/pageattr.c >> +++ b/arch/riscv/mm/pageattr.c >> @@ -401,6 +401,22 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid) >> return __set_memory((unsigned long)page_address(page), nr, set, clear); >> } >> >> +int folio_zap_direct_map(struct folio *folio) >> +{ >> + int ret; >> + >> + ret = set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), false); >> + >> + return ret; >> +} >> + >> +int folio_restore_direct_map(struct folio *folio) >> +{ >> + return set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), true); >> +} >> + >> #ifdef CONFIG_DEBUG_PAGEALLOC >> static int debug_pagealloc_set_page(pte_t *pte, unsigned long addr, void *data) >> { >> diff --git a/arch/s390/include/asm/set_memory.h b/arch/s390/include/asm/set_memory.h >> index 94092f4ae764..fc73652e5715 100644 >> --- a/arch/s390/include/asm/set_memory.h >> +++ b/arch/s390/include/asm/set_memory.h >> @@ -63,6 +63,8 @@ __SET_MEMORY_FUNC(set_memory_4k, SET_MEMORY_4K) >> int set_direct_map_invalid_noflush(struct page *page); >> int set_direct_map_default_noflush(struct page *page); >> int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); >> +int folio_zap_direct_map(struct folio *folio); >> +int folio_restore_direct_map(struct folio *folio); >> bool kernel_page_present(struct page *page); >> >> #endif >> diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c >> index d3ce04a4b248..df4a487b484d 100644 >> --- a/arch/s390/mm/pageattr.c >> +++ b/arch/s390/mm/pageattr.c >> @@ -412,6 +412,24 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid) >> return __set_memory((unsigned long)page_to_virt(page), nr, flags); >> } >> >> +int folio_zap_direct_map(struct folio *folio) >> +{ >> + unsigned long addr = (unsigned long)folio_address(folio); >> + int ret; >> + >> + ret = set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), false); >> + flush_tlb_kernel_range(addr, addr + folio_size(folio)); >> + >> + return ret; >> +} >> + >> +int folio_restore_direct_map(struct folio *folio) >> +{ >> + return set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), true); >> +} >> + >> bool kernel_page_present(struct page *page) >> { >> unsigned long addr; >> diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h >> index 61f56cdaccb5..7208af609121 100644 >> --- a/arch/x86/include/asm/set_memory.h >> +++ b/arch/x86/include/asm/set_memory.h >> @@ -90,6 +90,8 @@ int set_pages_rw(struct page *page, int numpages); >> int set_direct_map_invalid_noflush(struct page *page); >> int set_direct_map_default_noflush(struct page *page); >> int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); >> +int folio_zap_direct_map(struct folio *folio); >> +int folio_restore_direct_map(struct folio *folio); >> bool kernel_page_present(struct page *page); >> >> extern int kernel_set_to_readonly; >> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c >> index 6c6eb486f7a6..3f0fc30eb320 100644 >> --- a/arch/x86/mm/pat/set_memory.c >> +++ b/arch/x86/mm/pat/set_memory.c >> @@ -2656,6 +2656,26 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid) >> return __set_pages_np(page, nr); >> } >> >> +int folio_zap_direct_map(struct folio *folio) >> +{ >> + unsigned long addr = (unsigned long)folio_address(folio); >> + int ret; >> + >> + ret = set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), false); >> + flush_tlb_kernel_range(addr, addr + folio_size(folio)); >> + >> + return ret; >> +} >> +EXPORT_SYMBOL_FOR_MODULES(folio_zap_direct_map, "kvm"); >> + >> +int folio_restore_direct_map(struct folio *folio) >> +{ >> + return set_direct_map_valid_noflush(folio_page(folio, 0), >> + folio_nr_pages(folio), true); >> +} >> +EXPORT_SYMBOL_FOR_MODULES(folio_restore_direct_map, "kvm"); >> + >> #ifdef CONFIG_DEBUG_PAGEALLOC >> void __kernel_map_pages(struct page *page, int numpages, int enable) >> { >> diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h >> index 3030d9245f5a..8d1c8a7f7d79 100644 >> --- a/include/linux/set_memory.h >> +++ b/include/linux/set_memory.h >> @@ -40,6 +40,16 @@ static inline int set_direct_map_valid_noflush(struct page *page, >> return 0; >> } >> >> +static inline int folio_zap_direct_map(struct folio *folio) >> +{ >> + return 0; >> +} >> + >> +static inline int folio_restore_direct_map(struct folio *folio) >> +{ >> + return 0; >> +} >> + >> static inline bool kernel_page_present(struct page *page) >> { >> return true; >> -- >> 2.50.1 >> >>