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b=Ur5AWO7gR/EbdOkHyt0zSPjUSRWOvbKnLYxi2SIB6aa3Lw07eZbQcaaveO8dbyFIz DxgDdE8bYmMTQ4WUyFOsPLtcPgv8pFsJm0zacnNwDrh28AwA9Wg24MECYdP9hFx6UU GHMKZz50SFXq25g3V+T/EJTW5jrgDAkIXbHevcRV9nsvgJsPc/cenqrQXtcnrEhgRp 6ISbEj8RRVQ1c7Nursl4ntsqbuRirELzECvjuVl2L32LrD2kcSOc56KipX1QBUb6QV kSrBHlPE93sJHrOgFH78l4HvnLJfZz4NsP+Ally3Sxvx2ml3kJBBgbEyDc6rB5NqHE 5FLJsz2UFKDig== Message-ID: Date: Mon, 28 Sep 2026 10:53:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: uffd-missing-wp: add GC related functionality test To: Martin Cracauer , akpm@linux-foundation.org, linux-mm@kvack.org Cc: ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, peterx@redhat.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Stat-Signature: 7wz154sdq1dzdgmxmkcdqpb3ka7o9pru X-Rspam-User: X-Rspamd-Queue-Id: 6F85AA0005 X-HE-Tag: 1790585597-585517 X-HE-Meta: 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 lKfu5rJT UL6CMTeFshFnCiS2JbSKPK1l+whqLgdFTktvUc2/UBZ/ltYiXcm/cvJSNpUDBwn+O2UXHPRM51xv5OsmSYkTW7D1PiJIVovW/HDWClXvVffoZynujUMMri2V8dgm2VH87dxfyF+upmW1dB9Zjb3umuXzlYFheDzyM/HjBmFA6Wsfo2u4BmnkeTQOuDOzqWMInL1UIgV/x8qU06Ln5tRF6Ngyn+Lymq1N5im2DVqQpCWi9NBYaKEYqdOUL4cWcFFw4Dtb1gtj/lEWPZaKJ2+WV50Y3BEgz+wAYWEveVbIhX2Baf8KbBRwz7FAJyf+FQtuE2wXw Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/28/26 05:26, Martin Cracauer wrote: > Add a test that asserts that functionality needed for generational > garbage collection works. Namely to implement a write barrier using > userfaultfd instead of using segmentation faults. The planned target > is the GC in SBCL. > > The real GC will initially fill heap pages by using on-demand loading > of pages from an image file, either via mmap(2) or using userfaultfd > to decompress a page read from an image file made from individually > compressed blocks. This test doesn't do that so that it needs no disk > I/O and no decompression library. Instead, a fault will be filled by > copying page content from prepared pages in the heap. > > Assisted-by: Anthropic:Opus-5.5 > Signed-off-by: Martin Cracauer > --- > tools/testing/selftests/mm/Makefile | 1 + > tools/testing/selftests/mm/uffd-missing-wp.c | 413 +++++++++++++++++++ > 2 files changed, 414 insertions(+) > create mode 100644 tools/testing/selftests/mm/uffd-missing-wp.c Isn't something like that a better fit for LTP? -- Cheers, David