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[79.242.58.5]) by smtp.gmail.com with ESMTPSA id ay15-20020a5d6f0f000000b0033b4ebc3c8fsm7090793wrb.2.2024.02.12.05.54.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Feb 2024 05:54:29 -0800 (PST) Message-ID: Date: Mon, 12 Feb 2024 14:54:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 19/25] arm64/mm: Wire up PTE_CONT for user mappings To: Ryan Roberts , Mark Rutland Cc: Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240202080756.1453939-1-ryan.roberts@arm.com> <20240202080756.1453939-20-ryan.roberts@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 65B6BC0003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: oucd578p46qtfuhbnp1wap58ejocafz4 X-HE-Tag: 1707746073-632698 X-HE-Meta: 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 4e+c1wym 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 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: >> If so, I wonder if we could instead do that comparison modulo the access/dirty >> bits, > > I think that would work - but will need to think a bit more on it. > >> and leave ptep_get_lockless() only reading a single entry? > > I think we will need to do something a bit less fragile. ptep_get() does collect > the access/dirty bits so its confusing if ptep_get_lockless() doesn't IMHO. So > we will likely want to rename the function and make its documentation explicit > that it does not return those bits. > > ptep_get_lockless_noyoungdirty()? yuk... Any ideas? > > Of course if I could convince you the current implementation is safe, I might be > able to sidestep this optimization until a later date? As discussed (and pointed out abive), there might be quite some callsites where we don't really care about uptodate accessed/dirty bits -- where ptep_get() is used nowadays. One way to approach that I had in mind was having an explicit interface: ptep_get() ptep_get_uptodate() ptep_get_lockless() ptep_get_lockless_uptodate() Especially the last one might not be needed. Futher, "uptodate" might not be the best choice because of PageUptodate() and friends. But it's better than "youngdirty"/"noyoungdirty" IMHO. Of course, any such changes require care and are better done one step at at time separately. -- Cheers, David / dhildenb