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Tue, 09 Jul 2024 21:07:15 -0700 (PDT) Received: from [172.20.2.228] ([4.28.11.157]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6ab7d38sm23489205ad.137.2024.07.09.21.07.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jul 2024 21:07:15 -0700 (PDT) Message-ID: Date: Wed, 10 Jul 2024 06:07:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: Fix PTE_AF handling in fault path on architectures with HW AF support To: Ram Tummala , akpm@linux-foundation.org, fengwei.yin@intel.com Cc: willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, apopple@nvidia.com, stable@vger.kernel.org References: <20240710000942.623704-1-rtummala@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: <20240710000942.623704-1-rtummala@nvidia.com> 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-Stat-Signature: ikzkf3uqq6rac4ncz1fi5ozqmyqwzdbe X-Rspam-User: X-Rspamd-Queue-Id: 195638001E X-Rspamd-Server: rspam02 X-HE-Tag: 1720584440-767248 X-HE-Meta: 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 4sJCBYMs 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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: On 10.07.24 02:09, Ram Tummala wrote: > Commit 3bd786f76de2 ("mm: convert do_set_pte() to set_pte_range()") > replaced do_set_pte() with set_pte_range() and that introduced a regression > in the following faulting path of non-anonymous vmas on CPUs with HW AF > support. > > handle_pte_fault() > do_pte_missing() > do_fault() > do_read_fault() || do_cow_fault() || do_shared_fault() > finish_fault() > set_pte_range() > > The polarity of prefault calculation is incorrect. This leads to prefault > being incorrectly set for the faulting address. The following if check will > incorrectly clear the PTE_AF bit instead of setting it and the access will > fault again on the same address due to the missing PTE_AF bit. > > if (prefault && arch_wants_old_prefaulted_pte()) > entry = pte_mkold(entry); > > On a subsequent fault on the same address, the faulting path will see a non > NULL vmf->pte and instead of reaching the do_pte_missing() path, PTE_AF > will be correctly set in handle_pte_fault() itself. > > Due to this bug, performance degradation in the fault handling path will be > observed due to unnecessary double faulting. > > Cc: stable@vger.kernel.org > Fixes: 3bd786f76de2 ("mm: convert do_set_pte() to set_pte_range()") > Signed-off-by: Ram Tummala > --- Acked-by: David Hildenbrand -- Cheers, David / dhildenb