From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D2B41CA0FFD for ; Mon, 1 Sep 2025 13:05:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ABE658E001E; Mon, 1 Sep 2025 09:04:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A963E8E000F; Mon, 1 Sep 2025 09:04:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 984F18E001E; Mon, 1 Sep 2025 09:04:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 816C68E000F for ; Mon, 1 Sep 2025 09:04:00 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id EDEE4C0822 for ; Mon, 1 Sep 2025 13:03:59 +0000 (UTC) X-FDA: 83840698998.11.7A18251 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf26.hostedemail.com (Postfix) with ESMTP id 7C6D114000D for ; Mon, 1 Sep 2025 13:03:57 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=S95nPi2+; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf26.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1756731837; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4S/AvwRukxKIejg9tsdip6CFv4zbua8sXt7imfRAS/s=; b=SKZXBMM/w+5Au6kb/4uIOiSijYLXzuWSTMvk64hsKWE86XHOAd+CpA4EWuGF6+MckMNzqb WZwiXunAI9FBfeV/PVgsYQ80akW4VVKF4TIcGQ4mDda4QqlZm2E9ry8OJJ3azTiqRQ+zRy CIjDTi472S0E4CSNQ711h0bPend/XYQ= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=S95nPi2+; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf26.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1756731837; a=rsa-sha256; cv=none; b=mlV6RAocgTgNOgpdtLayhPv1Iv9Qs8lS7B4ZpliWlh1Ew08/hcM3+21prpZz9kFN6Gz4HZ CT+PFt7NWKr227Vi+bMFzF1IQZ5Q8NACXWLr/ibqJm44/6bTnDPiUFV4+mkMx0bGor2gmH t5RtanonRZovgxKNtwCGqMtxt7vsKbQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756731836; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=4S/AvwRukxKIejg9tsdip6CFv4zbua8sXt7imfRAS/s=; b=S95nPi2+3yxUtBUbqS061/CRTlIjweqyL11HT95hE0K4nXMGvlB/IP2KIWrJlpB6NU/IWF 5Oy+VIOHu+mCPyCwlX0VA7MPnqcsd9jskAOgqcFOmt8sOVTOwQ7+iJ9l07Kgz/+Zu9Uett w4IeapYL12p4UTWa3ttDTGbmrMW17ek= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-562-jLdsSNTuNtSw3lbvoQdvFA-1; Mon, 01 Sep 2025 09:03:55 -0400 X-MC-Unique: jLdsSNTuNtSw3lbvoQdvFA-1 X-Mimecast-MFC-AGG-ID: jLdsSNTuNtSw3lbvoQdvFA_1756731834 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-45b8a307c12so6214955e9.2 for ; Mon, 01 Sep 2025 06:03:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756731834; x=1757336634; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=4S/AvwRukxKIejg9tsdip6CFv4zbua8sXt7imfRAS/s=; b=sC6aLN1k5reaDHmZBZYlTvDTKAyLrmfxjDK9D1wxghyrzFJGfNjwzlvh/eNOx3LF6K lx1Yz8VCvkYrQ0dsn/FVI4dKcTqbk+LdZitpc0GZItL8AyMTfElRQnEG9gX5p2wOTV/i E4DpMI7l2+7Og1RGhvAW0coObS7HMwYPJl5ep8al5dV7LkmG3K0lkHUVzeCcotsPQEQ0 9dwqNOy7hpFwCWbLMwN2pyosuvocK8KBR+KUBxE9j1Xli0zOjbIdxbwumsSnEkXb+jtU aZUaW61/EZQSHsayBY4RPhMNI7eNI7h2LjJSVfbI5+ZLD6pMXG5nyGMMIiPHLwUxnxfA ddpg== X-Forwarded-Encrypted: i=1; AJvYcCWXbnGUTU4rMVlg+T7daP7TB4Qp99KvtZlV3KArTVAZoZrEqIdS3ft75lnXgeMmJe8Pg2Mn3UaitA==@kvack.org X-Gm-Message-State: AOJu0Ywb43tE8u6/d6QzhxUrmsSszsZMohIwyVo3cSPH/8cgxhqYz2Cd M9R5LBVdBX9pDawf2mfoZT/yCDqOuYCmAAn/HjWSH92wt8H1m7lSkjoe+ttJyHlq5pD0BfOWSSA Y9YpGT8Qr9NmmNNVAmLiCVXKrGjgVGTTAutDVSjaqEuKXBApnEL6Y X-Gm-Gg: ASbGnctR7ge4D8oWdPaQcC+9yl3Ji/3VekgACQi1MRm4Vew3EkYuTpKPzmutmqxc5va 3kOcAGSkXb4rwH1nyR8SzZ+Sunr46LQUcbFYUOEHvc6rSo+Qd0/0u/5Ul3UDzjjS8jLE0QapEIX m7UBogv8ivmv3MpY0UM+R7ecU78qQjbAyxsChXCdz8OckB7a3qjAjn64te6loo/6n5YGbJpIC1E ISqEdgvoQnEJMNv3cb3s+SF20Cjbuu8bUZnconj7NiOoTpe64K6AfsoOM29sS6FW3KVLzKy7FUY 8dtA9LIPQsZ1OOiLvytqiLB19feKAsV/OxC8L56pqaN8Pj/VOqD0vLIltJXZzVIcV39Yf9Ge9yU dzhMLoiRHA0aKHRE8MS+dvP/XiYnTipSu5eF4BtNb350LHOkcZQkTVSbylN1MLQD9OqA= X-Received: by 2002:a05:600c:3baa:b0:45b:8b3e:9f7b with SMTP id 5b1f17b1804b1-45b8b3ea15cmr36229275e9.3.1756731834036; Mon, 01 Sep 2025 06:03:54 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFeSZT/6o5qBMANLK7aNiFwK9ljYFxoG5c9Qiw88K7oLWWH6nH+zDcxN4lJDLm0Ugp6jdmQyg== X-Received: by 2002:a05:600c:3baa:b0:45b:8b3e:9f7b with SMTP id 5b1f17b1804b1-45b8b3ea15cmr36228925e9.3.1756731833552; Mon, 01 Sep 2025 06:03:53 -0700 (PDT) Received: from ?IPV6:2003:d8:2f37:2b00:948c:dd9f:29c8:73f4? (p200300d82f372b00948cdd9f29c873f4.dip0.t-ipconnect.de. [2003:d8:2f37:2b00:948c:dd9f:29c8:73f4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf34491a65sm15061948f8f.56.2025.09.01.06.03.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Sep 2025 06:03:53 -0700 (PDT) Message-ID: <0a0b0018-9427-4201-bf53-6aeb251bc482@redhat.com> Date: Mon, 1 Sep 2025 15:03:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v2] selftests/mm: check content to see whether mremap corrupt data To: Zi Yan Cc: Wei Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20250831022701.2595-1-richard.weiyang@gmail.com> <61E58B7C-23D0-49FE-8D0C-CE0B672114E2@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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+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: <61E58B7C-23D0-49FE-8D0C-CE0B672114E2@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: cGiqCRDDC-UTyQx1HEq6v7sJEsjlqOr4kg8Ueta7enQ_1756731834 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: 7C6D114000D X-Stat-Signature: nodd5xme76ue5xd6e7rqt9cjf5ux9d6n X-Rspam-User: X-HE-Tag: 1756731837-676521 X-HE-Meta: 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 xc8wrx9O 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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 01.09.25 14:56, Zi Yan wrote: > On 1 Sep 2025, at 3:22, David Hildenbrand wrote: > >> On 31.08.25 04:27, Wei Yang wrote: >> >> Subject: "selftests/mm: verify page content after remapping PMD through PTEs" >> >>> After mremap(), add a check on content to see whether mremap corrupt >>> data. >>> >>> Signed-off-by: Wei Yang >>> >>> --- >>> v2: add check on content instead of just test backed folio >> >> I'm confused, don't we have that exact check later in the function? >> >> Your v1 might have been better, unless I am missing something. >> >>> --- >>> tools/testing/selftests/mm/split_huge_page_test.c | 6 +++++- >>> 1 file changed, 5 insertions(+), 1 deletion(-) >>> >>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c >>> index 10ae65ea032f..229b6dcabece 100644 >>> --- a/tools/testing/selftests/mm/split_huge_page_test.c >>> +++ b/tools/testing/selftests/mm/split_huge_page_test.c >>> @@ -423,10 +423,14 @@ static void split_pte_mapped_thp(void) >>> /* smap does not show THPs after mremap, use kpageflags instead */ >>> thp_size = 0; >>> - for (i = 0; i < pagesize * 4; i++) >>> + for (i = 0; i < pagesize * 4; i++) { >>> + if (pte_mapped[i] != (char)i) >>> + ksft_exit_fail_msg("%ld byte corrupted\n", i); >>> + >>> if (i % pagesize == 0 && >>> is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) >>> thp_size++; >>> + } >>> if (thp_size != 4) >>> ksft_exit_fail_msg("Some THPs are missing during mremap\n"); >> >> I'm a bit confused with this test in general. >> >> We do a >> >> pte_mapped = mremap(one_page, pagesize, pagesize, MREMAP_MAYMOVE); >> >> which I read as a "NOP". >> >> Questions >> >> (a) Will this actually do anything? Also, maybe it does now, but can't the kernel just optimize that out in the future? > > It remaps each subpage of 4 PMD THPs into a contiguous 2MB vaddr range and > perform split on that range. I'm afraid I am missing the "why". I would have thought that a "split_pte_mapped_thp" test would want to pte-map THPs to the see if they can be split. Why is the mremap required? IOW, what exactly is the test trying to test that exceeds "split_pte_mapped_thp" ? -- Cheers David / dhildenb