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[2003:cb:c72c:5800:458e:8c41:4802:47f9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-429ed650903sm46716195e9.18.2024.08.17.04.05.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 17 Aug 2024 04:05:58 -0700 (PDT) Message-ID: <5daf183d-6942-4fcf-a5e2-dee022da89d8@redhat.com> Date: Sat, 17 Aug 2024 13:05:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 09/19] mm: New follow_pfnmap API To: Sean Christopherson , Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador , Jason Gunthorpe , Axel Rasmussen , linux-arm-kernel@lists.infradead.org, x86@kernel.org, Will Deacon , Gavin Shan , Paolo Bonzini , Zi Yan , Andrew Morton , Catalin Marinas , Ingo Molnar , Alistair Popple , Borislav Petkov , Thomas Gleixner , kvm@vger.kernel.org, Dave Hansen , Alex Williamson , Yan Zhao References: <20240809160909.1023470-1-peterx@redhat.com> <20240809160909.1023470-10-peterx@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6AAA218001A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 1kcnbgsnqjn1czys97x7wwpcze3zoo11 X-HE-Tag: 1723892764-631008 X-HE-Meta: U2FsdGVkX1+EEmcsLwnBFGjj42YM2tEMIuPkndFtALpgGAyiP5k5Ev4SAs3446LZIeDzPYcMLQ00TW12dJmNFk+GqO6miZRXgsB0y7BG++Rp7mSC2yaVJWFSGoi78GYzgDMf4L2gEJ+RwhJtPJ7oeiVq9Rs5j8Edm7pnIX49JscJSF/8StzkFmWFYVbtLg6ZmkmLO6+fwFavjyS5ayzr/l+OeKi3SN4JkVrjo8JRJv5zboX/qXYDG8nLMlWSqKeOtytQwJoNU95Kd7Xa24wGTURusuLAqFmDVFSEcZU99wG0P2HF3Bn6KKJQA9N4J4hrzvPARc2SG+kMCKAXOVg7OH0dIe28v6VKdKzDoCulxOJWVBdQ/19RVxr2toM1fbHfTKRe+EqMgsHX7EpLFKFzf/9AUE7kBIcVHohOkarenErsdH8Qbx/WjUIojShzT1tJRnevN3aRPJ6Nu9KCZV5N9wZd4O5nx4SmfOV7bcFDD2xYz+FxNuTfnkVMjt14dIIh26TZek45fySpV334IUZvXPe9LAnprXmanvDcfmUTyItf3nTmZcN3iXP2gWYIDPClrjkJOGgoG1/WNG/QsPzxdpS4iKeDApMO2EGNrbnLudysO8mh6E5Ao+p1VPe9eb0XB24ogDnMWwTZh4E11bECbQi8pIULGeDw3zcBY6mxN583cpOz0EnrEG3rthvA3wPQ1+etSvsYi8LW8iUyMiChrKOQapKw4xuuUE8gJj6pkD9YiF3FnFhm1E8ZKIF/LTzwxqOLBvTLHLS69kiFn+xhpmcZGhOayEEbWk0xW+e1U+Q8tLT1fkelbAYspYsHYIOmKrLGTgHHnAVjqivFzvxkXz/zoqbvuDU0IlAEZbdgIvdH35KGYd9FowzEgr5bNbrf7ZKLe+VCgNaWA8WzBBMwysy/JJMM1gwDGFmg2zCBH4T6zOZ042ZgR7FOtb05pjGfbuBrdRPfmwunjOxj/8r MFaAvCn6 yGmr35BYw2JgjYUgV6XYyKIaGlJKsL/RJZa1u2B2Zv9XTWR8J8HV4GkaEU6eNNf3gL9Q9jCYdd+WrABP+EVLkso4Sg4Txt60zDPqd9mdbwxDpGT0Xahau85zDQJ8E8te6Os0j7k/VT+yE6T7n+dCP/pZ5PZSfsO5P5IEiadrKtIYRCBnMbdtSkRME5arXq/PvC8FhNUgPbX75mVMbhpMCmbUzfg0ZxsvVYtQjVbhSA5+Rxm4ohIYsIMVoaOTpe9Z7vIF8O/DJo6eF0D+UVJC8Ur+lVLfFBLO7Ljg30f7AXJwiNHh+mf2JEvk92kbSRU3eCKQvUUAhzYa6wKBRjTKwFWxBGIhoWdcZ8u/5QC+LtZmJmuYUk4cGoEELgCDI8my4wa/EQa8sQrV5M+KU7IPrdmyluXcwlD2Tk66i+YWHGTUqpto= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, 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 17.08.24 01:12, Sean Christopherson wrote: > On Fri, Aug 09, 2024, Peter Xu wrote: >> Introduce a pair of APIs to follow pfn mappings to get entry information. >> It's very similar to what follow_pte() does before, but different in that >> it recognizes huge pfn mappings. > > ... > >> +int follow_pfnmap_start(struct follow_pfnmap_args *args); >> +void follow_pfnmap_end(struct follow_pfnmap_args *args); > > I find the start+end() terminology to be unintuitive. E.g. I had to look at the > implementation to understand why KVM invoke fixup_user_fault() if follow_pfnmap_start() > failed. It roughly matches folio_walk_start() / folio_walk_end(), that I recently introduced. Maybe we should call it pfnmap_walk_start() / pfnmap_walk_end() here, to remove the old "follow" semantics for good. > > What about follow_pfnmap_and_lock()? And then maybe follow_pfnmap_unlock()? > Though that second one reads a little weird. Yes, I prefer start/end (lock/unlock reads like an implementation detail). But whatever we do, let's try doing something that is consistent with existing stuff. -- Cheers, David / dhildenb