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Mon, 8 Dec 2025 09:02:16 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id vluqGRiUNml/AgAAD6G6ig (envelope-from ); Mon, 08 Dec 2025 09:02:16 +0000 Message-ID: <8828d51f-bbcf-4d08-b99f-a2cf64fe4b75@suse.cz> Date: Mon, 8 Dec 2025 10:02:15 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 03/13] mm: introduce AS_NO_DIRECT_MAP Content-Language: en-US To: John Hubbard , "Kalyazin, Nikita" , "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@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@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" , "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" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "shuah@kernel.org" , "riel@surriel.com" , "baohua@kernel.org" , "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" , "isaku.yamahata@intel.com" , "jmattson@google.com" , "jthoughton@google.com" , "linux-arm-kernel@lists.infradead.org" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" References: <20251205165743.9341-1-kalyazin@amazon.com> <20251205165743.9341-4-kalyazin@amazon.com> <3d26bfb2-2c82-4625-a371-96879ff43c3d@nvidia.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A0F2340008 X-Stat-Signature: ucjy8e14oqt9fkphg9j3xzqjxwgszfzn X-Rspam-User: X-HE-Tag: 1765184539-453510 X-HE-Meta: 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 suQoaN0q h6d1JzXMuqGhWaNGTJ/JUWCSX+u23oxRShoh2IMJwnh0quOlqmkpr7vTt06XnXf46kEB5ydCoBaUNEmJmmR2REOQGLhzYOoMWUzDt49YoevzPn0cYJtRyEW7YXQtDHEmV3VHW1XgX/sWVlz5t2AclAKqhIQAoOG8raMKBW5ywCK5xBYoRSVC2q+0FRwHODi1Kri7Aowb/6wCZPwyBoZWMlWDjpfD16xtTHN2Ar+z8hubY7PavUTCfU9roXAE3AxzKi1q718X9SwRFkrCHq54RRtlL9ADvVV9mvm7kP3iJ2qlZiyNyRqLDcMwQEDv4KKXGeLPgmMge+5TKLLt2thepePyV1KoxqRKdb8IvPV5+IZWoxI+rit6oF9zW26dk61hTRXEXGGOzxU1FqFKmfVCpZKCbq5QgDAyC2JrODKStlliODgwNf6yOionfLLGI2P8DcIKV 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 12/5/25 19:35, John Hubbard wrote: > On 12/5/25 8:58 AM, Kalyazin, Nikita wrote: >> From: Patrick Roy >> >> Add AS_NO_DIRECT_MAP for mappings where direct map entries of folios are >> set to not present. Currently, mappings that match this description are >> secretmem mappings (memfd_secret()). Later, some guest_memfd >> configurations will also fall into this category. >> >> Reject this new type of mappings in all locations that currently reject >> secretmem mappings, on the assumption that if secretmem mappings are >> rejected somewhere, it is precisely because of an inability to deal with >> folios without direct map entries, and then make memfd_secret() use >> AS_NO_DIRECT_MAP on its address_space to drop its special >> vma_is_secretmem()/secretmem_mapping() checks. >> >> This drops a optimization in gup_fast_folio_allowed() where >> secretmem_mapping() was only called if CONFIG_SECRETMEM=y. secretmem is >> enabled by default since commit b758fe6df50d ("mm/secretmem: make it on >> by default"), so the secretmem check did not actually end up elided in >> most cases anymore anyway. > > The above paragraph can be part (most) of a commit description for > a separate patch for the gup aspects. Let's split it out that way, > because it is a distinct change, and the diffs can stand alone > from this patch here. I assume the separated gup change will be ordered as the earlier one, because keeping "check_secretmem" together with newly checking mapping_no_direct_map() would be incorrect. Make sense. > thanks,