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b=OB3FKG2XQBSFfNl6yatDDLwkubGI3MTeie/zNm8/qluN6mhVq7k9oZd6suBLz8So2 mlXSyzGb4JjZkOe0yU1+kIdE2dygihuvnRdZJPvYuUhP+qDchhw5aUOabPa+90pPcx G9m1RMch34bOWQkpgakTvl0tQD53nVdMOM6tkN7yYCbyC2/HwNLHzE3PTPuUg0UN3l 3lfjaRVHX2n4RXWidrSrCFN+aPduJNuWAfZifP3NofAopZvQXDrIVghRcCN8UGGjGf SdamrQWFZfXGcySWnN1d5qiVmwA4jx1gcHocmJhZrcBnE1Y1XxPFWyPHEJA6AGNB18 tJsCRrNyw/jVw== Message-ID: Date: Thu, 26 Feb 2026 17:29:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/3] selftests/mm: Add UFFDIO_MOVE huge zeropage PMD regression test To: Chris Down , Andrew Morton Cc: Matthew Wilcox , kernel-team@fb.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@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-Queue-Id: 0C5562001A X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: fbxrz5xug1a3xk5fssb4q5fsymckuwru X-HE-Tag: 1772123396-873242 X-HE-Meta: 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 zU+X1WdF M0/GkQeT9+A7coa/YryNGTVFJ2d7FNnXC7LiPtchTCL6LgqenC5vA1y76gTBk7L5Q6NXLK9Pwg/rTEOhE5P4/+W6HewjkPsyCVexVTdIYX9t0dK9LuxuLX9D4XXesyCkw9L7vtvLWjjb2eP/RN+nBOp+jJyPIGk8iAO6BOv4Gz//9vowx3dZulJi3ZqsrHtk7C6wUfycRJFahFoqEPblP76gfxLcZLoUUFfv3SH4GqCLyq8Q6zkH/d7cUccv/2ZAPw5tZJABXhtBi8/dTXMHC7JNu+gpMAL+vlTlzNIH5JPCFyrXro6P7HqwbYw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/26/26 15:18, Chris Down wrote: > The existing uffd-unit-tests move-pmd coverage exercises PMD-sized > UFFDIO_MOVE on anonymous THPs, but it does not force the huge zeropage > PMD path in move_pages_huge_pmd(). > > Add a dedicated anonymous UFFDIO_MOVE PMD test that exercises this > relatively comprehensively. > > Signed-off-by: Chris Down > --- > tools/testing/selftests/mm/uffd-unit-tests.c | 176 +++++++++++++++++++ > 1 file changed, 176 insertions(+) > > diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c > index 6f5e404a446c..372619e3906d 100644 > --- a/tools/testing/selftests/mm/uffd-unit-tests.c > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c > @@ -203,6 +203,62 @@ static int pagemap_open(void) > return fd; > } > Thanks for implementing this! [...] > +static bool uffd_pagemap_scan_get_categories(int fd, char *start, uint64_t *categories) > +{ > + struct page_region r = { 0 }; > + long ret; > + > + if (!uffd_pagemap_scan_supported(fd, start)) > + return false; > + > + ret = uffd_pagemap_scan_get_categories_raw(fd, start, &r); > + if (ret < 0) > + err("PAGEMAP_SCAN failed: %s", strerror(errno)); > + > + *categories = ret ? r.categories : 0; > + return true; > +} Can we unify (deduplicate) that code with what we have in vm_util.c, and then only export a function like bool pagemap_is_huge_zero(int fd, char *start) similar to pagemap_is_softdirty() etc to be consumed by the test here? It can simply return "false" in case the interface is not available. > + > /* This macro let __LINE__ works in err() */ > #define pagemap_check_wp(value, wp) do { \ > if (!!(value & PM_UFFD_WP) != wp) \ > @@ -1227,6 +1283,119 @@ static void uffd_move_pmd_test(uffd_global_test_opts_t *gopts, uffd_test_args_t > uffd_move_pmd_handle_fault); > } > > +static void uffd_move_pmd_huge_zeropage_test(uffd_global_test_opts_t *gopts, > + uffd_test_args_t *targs) > +{ > + unsigned long pmd_size = read_pmd_pagesize(); > + unsigned long pmd_pages; > + unsigned long bytes = gopts->nr_pages * gopts->page_size; > + char *orig_area_src = gopts->area_src, *orig_area_dst = gopts->area_dst; > + char *aligned_src, *aligned_dst; > + unsigned long src_offs, dst_offs, max_offs; > + pthread_t uffd_mon; > + struct uffd_args args = { 0 }; > + char c = '\0'; > + int pagemap_fd; > + uint64_t categories; > + unsigned long i; > + > + if (pmd_size <= gopts->page_size) { > + uffd_test_skip("huge page size is 0, feature missing?"); > + return; > + } > + if (!detect_huge_zeropage()) { > + uffd_test_skip("transparent huge zeropage disabled"); > + return; > + } > + > + pmd_pages = pmd_size / gopts->page_size; > + if (bytes < pmd_size) { > + uffd_test_skip("not enough pages for one PMD-sized move"); > + return; > + } > + > + aligned_src = ALIGN_UP(orig_area_src, pmd_size); > + aligned_dst = ALIGN_UP(orig_area_dst, pmd_size); > + src_offs = (aligned_src - orig_area_src) / gopts->page_size; > + dst_offs = (aligned_dst - orig_area_dst) / gopts->page_size; > + max_offs = src_offs > dst_offs ? src_offs : dst_offs; > + if (max_offs + pmd_pages > gopts->nr_pages) { > + uffd_test_skip("could not find aligned PMD-sized src/dst window"); > + return; > + } > + > + if (madvise(orig_area_dst, bytes, MADV_HUGEPAGE)) > + err("madvise(MADV_HUGEPAGE) failure"); > + if (madvise(orig_area_src, bytes, MADV_DONTFORK)) > + err("madvise(MADV_DONTFORK) failure"); > + if (madvise(aligned_src, pmd_size, MADV_DONTNEED)) > + err("madvise(MADV_DONTNEED) failure"); > + > + /* Materialise a PMD-sized huge zeropage mapping in the source. */ "Fault in the huge zeropage" > + force_read_pages(aligned_src, pmd_pages, gopts->page_size); > + > + pagemap_fd = pagemap_open(); > + if (!uffd_pagemap_scan_get_categories(pagemap_fd, aligned_src, &categories)) { > + close(pagemap_fd); > + uffd_test_skip("PAGEMAP_SCAN unsupported"); > + return; > + } > + if ((categories & (PAGE_IS_PRESENT | PAGE_IS_PFNZERO | PAGE_IS_HUGE)) != > + (PAGE_IS_PRESENT | PAGE_IS_PFNZERO | PAGE_IS_HUGE)) { > + close(pagemap_fd); > + uffd_test_skip("could not materialise a huge zeropage PMD mapping"); "could not fault in the huge zeropage" ? > + return; > + } > + gopts->area_src = aligned_src; > + gopts->area_dst = aligned_dst; > + > + if (uffd_register(gopts->uffd, gopts->area_dst, pmd_size, true, false, false)) > + err("register failure"); > + > + args.gopts = gopts; > + args.handle_fault = uffd_move_pmd_handle_fault; > + if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) > + err("uffd_poll_thread create"); > + > + /* > + * One fault on dst should trigger a single PMD-sized UFFDIO_MOVE from > + * the huge zeropage PMD we populated in the source. > + */ > + force_read_pages(gopts->area_dst, pmd_pages, gopts->page_size); > + > + if (write(gopts->pipefd[1], &c, sizeof(c)) != sizeof(c)) > + err("pipe write"); > + if (pthread_join(uffd_mon, NULL)) > + err("join() failed"); > + > + if (args.missing_faults != 1 || args.minor_faults != 0) { > + uffd_test_fail("stats check error"); > + } else if (!uffd_pagemap_scan_get_categories(pagemap_fd, gopts->area_dst, > + &categories)) { > + uffd_test_fail("PAGEMAP_SCAN unsupported"); Why should it suddenly be unsupported when it worked before? With the pagemap_is_huge_zero() helper, this will boil down to } else if (pagemap_is_huge_zero(...)) { uffd_test_fail("moved destination is not a huge zeropage PMD"); } > + } else if ((categories & (PAGE_IS_PRESENT | PAGE_IS_PFNZERO | > + PAGE_IS_HUGE)) != > + (PAGE_IS_PRESENT | PAGE_IS_PFNZERO | PAGE_IS_HUGE)) { > + uffd_test_fail("moved destination is not a huge zeropage PMD"); > + } else if (!check_huge_anon(gopts->area_dst, 0, pmd_size)) { > + /* vm_normal_page_pmd() must continue to treat the moved PMD as special. */ > + uffd_test_fail("moved huge zeropage PMD counted as AnonHugePages"); > + } else { > + for (i = 0; i < pmd_size; i++) { > + if (gopts->area_dst[i]) { > + uffd_test_fail("moved huge zeropage PMD data is not zero"); > + goto out_restore; > + } > + } That's a bit excessive given that pagemap told us that it is indeed the huge zeropage. So I would just drop this. -- Cheers, David