From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7ACEC25A2C9; Thu, 5 Mar 2026 17:35:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772732101; cv=none; b=XURwewBV8SSYRVYkmevXopJGum/RiVxQ/CI1FOJ3aA2jEPOkyjsSV8XMEQW4AWQujGPYaAlhAgt8DpkL3EcnImqhBUMzueR482++/WTvbhJDKRtPK1JTe6BcKdnoUWqPRsWFAWjDVsdyF4orXBNYGnImppb6GrcxqPwpY56ARLg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772732101; c=relaxed/simple; bh=56aRoAVzPeQ+dwVrdE3T5LIBh/tHK5LhrXeg2GPGARY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tTf54Mr5kqyr2ta0HrvfFW4GtJjf16YP240JOIIsHd4IZv8A+vMdjepaVbMoOso35PLZWs2Rr9ICTsIFxVNvPOsShjrDcW0ULTYflfHgU7Tj763RZVtzvha1pnf4BjDptx8d2+j4NxdBR6bvoMz7pFhpbvoWFPykRCSnUmt6kl0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SNJUfyAa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SNJUfyAa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFEACC19425; Thu, 5 Mar 2026 17:34:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772732101; bh=56aRoAVzPeQ+dwVrdE3T5LIBh/tHK5LhrXeg2GPGARY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SNJUfyAa+pOGSpSVWJhLtY5AZnRO7etbHovFucUT8TXtqWY9985XSqGU8RMWCDSMd 1ZFYbjOd3UTSfkRHwfCNAbUOR8czgn3AP5sdfd3NDuMTwlejtHcBQywUKbAkce4nTe dEwNcN9AYGiADUff+P0WNpX+woEHoHermioN+npeoYqsCJHEP5pDpw9nhdmbj8i1n9 S8ZG8tpuRHozTfhieeF2eQimOT3Mr+dJeCNLypIAETyKi3durz59wMY2erlZRNGn7t n1IaS6Ru9j6oE8qY8qN5jctLVXgDfFP9P0eHUpDtsiPtIGlce9evGXASnm9NnTQCF0 DnFXPOqZ3moTA== Message-ID: Date: Thu, 5 Mar 2026 18:34:35 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 02/15] 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" 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@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" , "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" , "Cali, Marco" References: <20260126164445.11867-1-kalyazin@amazon.com> <20260126164445.11867-3-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: <20260126164445.11867-3-kalyazin@amazon.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/26/26 17:47, 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. "Let's provide folio_{zap,restore}_direct_map helpers as preparation for supporting removal of the direct map for guest_memfd folios. ... > > 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. Would it be possible to convert mm/secretmem.c as well? There, we use set_direct_map_invalid_noflush(folio_page(folio, 0)); and set_direct_map_default_noflush(folio_page(folio, 0)); Which is a bit different to below code. At least looking at the x86 variants, I wonder why we don't simply use set_direct_map_valid_noflush(). If so, can you add a patch to do the conversion, pleeeeassse ? :) > > Reviewed-by: Ackerley Tng > 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 | 12 ++++++++++++ > arch/riscv/include/asm/set_memory.h | 2 ++ > arch/riscv/mm/pageattr.c | 12 ++++++++++++ > arch/s390/include/asm/set_memory.h | 2 ++ > arch/s390/mm/pageattr.c | 12 ++++++++++++ > 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, 88 insertions(+) > > diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h > index c71a2a6812c4..49fd54f3c265 100644 > --- a/arch/arm64/include/asm/set_memory.h > +++ b/arch/arm64/include/asm/set_memory.h > @@ -15,6 +15,8 @@ int set_direct_map_invalid_noflush(const void *addr); > int set_direct_map_default_noflush(const void *addr); > int set_direct_map_valid_noflush(const void *addr, unsigned long numpages, > 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 e2bdc3c1f992..0b88b0344499 100644 > --- a/arch/arm64/mm/pageattr.c > +++ b/arch/arm64/mm/pageattr.c > @@ -356,6 +356,18 @@ int set_direct_map_valid_noflush(const void *addr, unsigned long numpages, > return set_memory_valid((unsigned long)addr, numpages, valid); > } > > +int folio_zap_direct_map(struct folio *folio) > +{ > + return set_direct_map_valid_noflush(folio_address(folio), > + folio_nr_pages(folio), false); > +} > + > +int folio_restore_direct_map(struct folio *folio) > +{ > + return set_direct_map_valid_noflush(folio_address(folio), > + folio_nr_pages(folio), true); > +} Is there a good reason why we cannot have two generic inline functions that simply call set_direct_map_valid_noflush() ? Is it because of some flushing behavior? (which we could figure out) In particular, a single set of functions could have a beautiful centralized kerneldoc, right?! :) -- Cheers, David