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(p200300cbc74eff00f73402276936cdab.dip0.t-ipconnect.de. [2003:cb:c74e:ff00:f734:227:6936:cdab]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a06d532976sm2031062f8f.73.2025.04.24.05.52.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Apr 2025 05:52:09 -0700 (PDT) Message-ID: Date: Thu, 24 Apr 2025 14:52:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] kernel/fork: only call untrack_pfn_clear() on VMAs duplicated for fork() To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, Andrew Morton , Ingo Molnar , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Rik van Riel , "H. Peter Anvin" , Linus Torvalds References: <20250422144942.2871395-1-david@redhat.com> <45b26168-93c9-4170-b7e1-4b51078a04f6@lucifer.local> <33b972a5-a137-4b5f-846c-614e5f83409f@lucifer.local> <0101d903-af59-478d-b0e6-af5ba6619eff@redhat.com> <7aeaa30d-3fa6-4edf-82a0-e0c494ef3df8@lucifer.local> <9f78fd5e-a785-4473-8c6b-8267821db446@redhat.com> <9a9103db-95ca-47d4-921e-42b8368ffcaf@lucifer.local> 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: <9a9103db-95ca-47d4-921e-42b8368ffcaf@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: LwJnt37k2Vt_iyD-0sa1eSSHQSpsVw12nhZzrVGGGoE_1745499130 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: rspam06 X-Rspamd-Queue-Id: E6460180014 X-Stat-Signature: ur7xpujifgocw9h3bd8hizdgtftxsrmb X-Rspam-User: X-HE-Tag: 1745499134-975164 X-HE-Meta: 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 YluXjZ0Q TygO8Y/DiXL9vS8eQDRWJKzl8zjD+lwEAUc3qzylnBka8MyRjKaIKflheegCsdTf6lvNAlTsahBFig0Ytqixv8oOzfl0v4nU1Zy6ydNHh4/VPnFfmyT2QsW9rRPU2khXTZTSoCDz2e0tsw+l8oVOA0u3j7/x3AO0Vx9GWS2YIXnv+vyRSGgf1kcympOA5t4UUdnf17NQC/y7DaEIwvW0WBILcLV8DjZ5z2k2xcBTghdMVBem9ks+5pR03CjjXOkFFsZL0q+HbwGD+5o2Ahu3+BU2JasMMy6S5nvzNQszBXbJM2LFSLnbbsaxHO4+4IGElFyepAx8zyQz9cHXibriu4WXqmPD2Q6NP40xo5tX/DSy2cN8yE5Q2A1uVs5pCypeiXpTbXPRDZXlh+D/1AatJtzBs5r9RtBRLVpuawwYOqoEihaNlZB4XIptthZmY8WGdMP5gyBGJZ/f2iQY= 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: >>> But maybe I misunderstand your approach :) Happy to obviously look and if >>> not like some crazy thing just for PAT (you can understand why I would not >>> like this) will be supportive :>) >> >> This is something quick (well, longer than I wish it would take) that seems to >> work. There are smaller pat-internal cleanups to be had on top of this, and >> the new functions shall be documented. >> >> >> Observe how: >> * We remove VM_PAT and that weird VM flags manipulation + "locked" flag >> * We remove any traces of the nasty tracking handling from mremap+fork code >> * Just like anon_vma_name, it hooks into vm_area_dup()/vm_area_free(). >> * We remove the page table lookup via get_pat_info()->... completely >> * We remove the VMA parameter from PAT code completely >> * We reduce the track/untrack/sanitize interface to 3 functions > > Yeah this is all lovely! > > OK this should hopefully be workable then! Okay, let me polish that up (and see if there is any reasonable way to split it up), and write some doc+descriptions .. and do some more testing. The VMA split reproducer is definitely happy with this already. -- Cheers, David / dhildenb