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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3557CC5AE59 for ; Wed, 28 May 2025 07:55:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B3F9D6B008C; Wed, 28 May 2025 03:55:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B16A16B0092; Wed, 28 May 2025 03:55:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A2C766B0093; Wed, 28 May 2025 03:55:19 -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 860FB6B008C for ; Wed, 28 May 2025 03:55:19 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 185B71C9E4A for ; Wed, 28 May 2025 07:55:19 +0000 (UTC) X-FDA: 83491556358.20.FAE710F Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf25.hostedemail.com (Postfix) with ESMTP id CDBF2A000D for ; Wed, 28 May 2025 07:55:15 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=PDQbeQ95; spf=pass (imf25.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1748418916; 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=8k/igYlOW9WC3oP8pew70NosGqil1WbzrgjNzVMa5Qk=; b=3Yw9WnUASbv8GA0iM71nD/2Er8OotsFRb5fM8cXNyvyTi0CxcMEfCljGbph2hik0qmC1QP 4kyjejg9FBAeMG76YPYoJuVMyjNpOeEdHq9F31wOP7H6SaqUzj1aNRnXNd8ji3srsIaaaU GJseeu/ye3XNSPRYQrArHlj9GUpw404= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=PDQbeQ95; spf=pass (imf25.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1748418917; a=rsa-sha256; cv=none; b=dct83TLgeOxE73sydn6PuaLeMBezHMzW3PhI39IQZbWWWsMJTg+iwBIxUoEnF0n53iILyC HfwXB1UUin/+WPc4RRRG6aQ9FFLDy9XNPKnOlqBZ9RM+mQ9rW3lKwbwhtCNvweEh/jsh8l oNUJ/AIJAW1R+Ifi81RYvWx0KD4GO6c= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1748418915; 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=8k/igYlOW9WC3oP8pew70NosGqil1WbzrgjNzVMa5Qk=; b=PDQbeQ95PZYxcm1V3gKnC6X8Y4c23HCXli8WSaH6zGq+6YWPhCwPNveJuRXe4JM9NnJ69p x/i6P1eAm9STNj3oi9bvmEP+SjiYlKHiHVcFblDxSSvXy+pEZvv0blmWg36nVpfZX8nWYE fMf4FrW8QuL9jmLVs30z4SEd2mO/QtY= 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-7-Xh3upXSXP-GNngohhCIdxQ-1; Wed, 28 May 2025 03:55:12 -0400 X-MC-Unique: Xh3upXSXP-GNngohhCIdxQ-1 X-Mimecast-MFC-AGG-ID: Xh3upXSXP-GNngohhCIdxQ_1748418910 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-442fa43e018so2925175e9.0 for ; Wed, 28 May 2025 00:55:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1748418910; x=1749023710; h=content-transfer-encoding:in-reply-to:organization: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=8k/igYlOW9WC3oP8pew70NosGqil1WbzrgjNzVMa5Qk=; b=TaDJEviOd485sjxFnuLig6rGVuk6FUlYYkHxM6YUkFFNXB4tixn9GZnejG8BWxxeBC zmPPnxcIaqBS1UQ+Q5FdIefoWy7ZfQdTfg91C2za0CAwMX87/WVDJg1+fuJfi2UgKch3 zsmlR8mP22Ik5wGRvcNRuMMpHV51z0uZX5SxrQcpWW4spjSM/dOdO1/jnRjxvSWyw5Qs xkJxmdmmV6eb0aJ0bD1rPz5K//6ArHiYYvzby+Jx1km5sAOc33fziDTLrh11/w+qta0z DHKVG7e9+0ztRZopQ2WSwbq2YcEhvqWUuGv5wWO2IJ9AaHOIRmqcrvZn0YdjgOiZUu2h EKUQ== X-Forwarded-Encrypted: i=1; AJvYcCVD74XgbXRv1wDED9WDFz7ZNdsJyiTVodkGZkinZblHwZoF3fKEHF57t1HCft01rx7XYNYlqvqKZg==@kvack.org X-Gm-Message-State: AOJu0Yx/Zk+RG72Ixr9FLTT9+pFntxAOlNxCjWqTn0eDIfWjmnO0J0W1 NdribRxe+r8PbcyaCkzmUjY4z135uDjSk2Q9U6z1kXORMX8QUh43mwpNdKgGX0SRtvdGI/0Sj13 1k9qMxAMFIf0EFX3hZh2pb1ey6kCZoOjRydxHasajeVnaWWDYq4HXEByRFAoLXTA= X-Gm-Gg: ASbGncvX/DW6Fbst93zamRKT0gbTb7qFVtoAgQkGJofbIqhM+Ngq882Ej48tzu13kiM cH5C2XBQjGuMwpWVUABy5Jcs8Fr48u9ucH4cCselCpaOOQZZI9w6BKEJ9He7nfNteoZ0ICTOIfT 0byKSnf6vJLumkFF1ZPM0+MIoicYbgRduPO0Yn6rK4Pw4rGD6z3S9Huxykif4KlO52jxeYOAAza TuvytOEi8fxG1KrFAv+LWsYw51nHMgyeoylyH+BDupUNNqXWO5TTE35u+6vAdcO/+D7Qn4ksiEP OufPvPwa0i2DzRxfTozo6XIiCKSoxIRPtkDqQF9muXV6kFJHuh4mC35fRWwaZki6X4uyztidFBO 3jaLes5fqKnzIrZ0ccHBjMS5hQnyVnhlWtZmreQ0= X-Received: by 2002:a05:600c:3503:b0:439:5f04:4f8d with SMTP id 5b1f17b1804b1-44fd1a5be91mr30315905e9.12.1748418909696; Wed, 28 May 2025 00:55:09 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHzqKYB1nyhLHFHAT/kvLrzKNX4DwNHTzjKvJR7UvpZOdZBK1sXvRCDaisrRXCbLLEcrewbQw== X-Received: by 2002:a05:600c:3503:b0:439:5f04:4f8d with SMTP id 5b1f17b1804b1-44fd1a5be91mr30315485e9.12.1748418909115; Wed, 28 May 2025 00:55:09 -0700 (PDT) Received: from ?IPV6:2003:d8:2f30:ec00:8f7e:58a4:ebf0:6a36? (p200300d82f30ec008f7e58a4ebf06a36.dip0.t-ipconnect.de. [2003:d8:2f30:ec00:8f7e:58a4:ebf0:6a36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-450787d416bsm9025525e9.39.2025.05.28.00.55.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 May 2025 00:55:08 -0700 (PDT) Message-ID: Date: Wed, 28 May 2025 09:55:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: reply: [RFC] pin_user_pages_fast failure count increased To: Hyesoo Yu , Zhaoyang Huang Cc: jaewon31.kim@samsung.com, John Hubbard , "zhaoyang.huang@unisoc.com" , "surenb@google.com" , "Steve.Kang@unisoc.com" , Jaewon Kim , "linux-mm@kvack.org" , Jang-Hyuck Kim References: <4e2305d6-b067-4963-b16a-367a254d22c1@nvidia.com> <20250526074845.GA2848800@tiffany> <20250526093258.GA3489925@tiffany> <20250526111744epcms1p89d664f5cebd1e690730f32b66c24e3c0@epcms1p8> <20250528012329.GA1545287@tiffany> <20250528033626.GA1607193@tiffany> 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: <20250528033626.GA1607193@tiffany> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: d7hbo_JYdxV5iMS7Y65tXtzmh615w6zIIJ3_Lr9WUX0_1748418910 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CDBF2A000D X-Stat-Signature: e35xhig8858n153sce7ftt8uf4mmtmdf X-Rspam-User: X-HE-Tag: 1748418915-235438 X-HE-Meta: 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 juXC237t sT+mCcVfThargt8N1eT1oC+Dh9AYVqFIatP5Xq+IXrJd6CFoF38hh5nvTZgP/Db/2764HnC4R9c2/51+K6a2LpGQjX+LJSmAb4ieQvhWxZJ41DXNjC23ty2gl8zHBsYOzIv2hcRsmE7GCXgHCu6KprBaeByoyzmqbY78ir/aElP+SBsbxkSXkrnfU/642k7UgtO+xFjrKgAdc6kO/gbEDIBHgInGIvm4HowSzhEtLDXCEq4U= 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 28.05.25 05:36, Hyesoo Yu wrote: > On Wed, May 28, 2025 at 10:49:36AM +0800, Zhaoyang Huang wrote: >> On Wed, May 28, 2025 at 9:25 AM Hyesoo Yu wrote: >>> >>> On Mon, May 26, 2025 at 07:49:57PM +0800, Zhaoyang Huang wrote: >>> >>> Hello, Zhaoyang. >>> >>> I don't believe commit 1aaf8c was just intended to prevent an infinite loop. >>> The commit was introduced to allow pinning CMA memory in the pKVM on AOSP. >>> >>> That leads me to question whether the assumption that CMA can be long-term pinned is actually valid. >> That depends on the user of CMA, yes for my scenario since it worked >> for the guest os. For common scenario such as the file/anon mapping, >> the page will be judged as unpinnable for long-term and be migrated >> out of CMA area. > > Your scenario and the common scenarios can not be distinguished from the kernel API's perspective. > Even in common cases, the page may be in a non-LRU state temporiarily, and in such situations, > pinning CMA can lead to bugs - we've encountered multiple issues because of this. > Right. We just disallow long-term pinning CMA pages, because we don't know who the real owner is that would be okay with long-term pinning them. >>> >>> In my opinion, it might be more appropriate to revert that commit 1aaf8c and instead ensure >>> that pKVM avoids using CMA for memory that requires long-term pinning through GUP ? >> It is not a pkvm issue but a defect of applying FOLL_LONGTERM over >> non-LRU CMA pages. > > In include/linux/mm_types.h, the CMA should be migrated when FOLL_LONGTERM. > > * In the CMA case: long term pins in a CMA region would unnecessarily fragment > * that region. And so, CMA attempts to migrate the page before pinning, when > * FOLL_LONGTERM is specified. > > Given this, would it make sense to avoid using FOLL_LONGTERM in this code path ? If something is unbounded in time, FOLL_LONGTERM is the right thing to use. >>> >>> Alternatively, instead of changing the current logic that prevents longterm GUP from pinning CMA, >>> it would be better to propose a new patch that specifically addresses the pKVM scenario like adding new FOLL_flags ? >> I don't think so. pin_user_pages is an exported API which can't make >> assumptions over the caller. > > My point is not to base the patch on assumptions about the caller, > but to define a clear mechanism that ensures safe behavior in the intended scenario. > > For example, you can add FOLL_NO_MIGRATION and skip to migrate unpinnable pages. Not sure which exact semantics you have in mind. But failing if we would have to migrate might be ok. Not sure if the caller should worry about that, though: the caller should not have to worry about page placement in general. -- Cheers, David / dhildenb