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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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240817_040604_771302_2359BD3F X-CRM114-Status: GOOD ( 11.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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