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([2a01:599:922:1046:67aa:7b35:f780:c8fc]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38c2a1bb101sm2947300f8f.66.2025.01.24.06.39.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Jan 2025 06:39:19 -0800 (PST) Message-ID: Date: Fri, 24 Jan 2025 15:39:18 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Question] Are "device exclusive non-swap entries" / "SVM atomics in Nouveau" still getting used in practice? To: Jason Gunthorpe Cc: "linux-mm@kvack.org" , John Hubbard , nouveau@lists.freedesktop.org, Alistair Popple , DRI Development , Karol Herbst , Lyude Paul , Danilo Krummrich References: <346518a4-a090-4eaa-bc04-634388fd4ca3@redhat.com> <8c6f3838-f194-4a42-845d-10011192a234@redhat.com> <20250124141121.GY5556@nvidia.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: <20250124141121.GY5556@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: JqSOBtEATB8221Kik3xlvwocPnYqRnhy7mhLgi9T9i8_1737729561 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 27E8280010 X-Stat-Signature: py85e5179teseqgkuhb7htybowamqpno X-Rspam-User: X-HE-Tag: 1737729563-639908 X-HE-Meta: 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 oaYdqZyP 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.053787, 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 24.01.25 15:11, Jason Gunthorpe wrote: > On Fri, Jan 24, 2025 at 11:44:28AM +0100, David Hildenbrand wrote: > >> There are other concerns I have (what if the page is pinned and access >> outside of the user space page tables?). Maybe there was not need to handle >> these cases so far. > > I think alot of this depends on userspace following some restrictions > so that the pages are always convertible. Presumably if the userspace > breaks things then their atomic using GPU kernels will fault. > > So, from a kernel perspective, I'd suggest that creating a reasonable > set of conditions that userspace can follow to have it work reliably > is a reasonable goal. Yes, that's my assumption as well. If you register a page using io_uring as a fixed buffer and then trigger "device_exclusive" access, the page can still be read/written using io_uring and atomics might not work as expected. "Not supported". -- Cheers, David / dhildenb