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 41B33C5B552 for ; Fri, 30 May 2025 10:05:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B72836B00E9; Fri, 30 May 2025 06:05:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B1FC26B00E7; Fri, 30 May 2025 06:05:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 997A56B00E8; Fri, 30 May 2025 06:05:05 -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 745946B00CA for ; Fri, 30 May 2025 06:05:05 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 1C05E577D1 for ; Fri, 30 May 2025 10:05:05 +0000 (UTC) X-FDA: 83499140970.28.2049EFD Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf16.hostedemail.com (Postfix) with ESMTP id A003A18000E for ; Fri, 30 May 2025 10:04:59 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ImSv1a5m; spf=pass (imf16.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=1748599502; 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=JBPpoXRrGXk2+QAUGnfzfHq6wXrCHCzvYZZhParVV0Q=; b=Ck3ZgCSIF1GfyE2f42rZOSUlqlKhV2QOPECOt7Rb0w3yVcGnHzr2E7LelFtCDBDeJA11U3 yT7+i+BIV4QxyL8KUg8nfvyw6r0lLuG/13nTlGyemOJPDQHmBiQptcT0iDk1m6153BTZhb N3fuGSk63HMNOZMsAOS/FQG2+vAwDks= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=ImSv1a5m; spf=pass (imf16.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=1748599502; a=rsa-sha256; cv=none; b=XoBjlAl/C6TP8bG9T5xwV3WZ4tMYv7OURrSrwat1PSAvs+r/2uJ5gPcAGfTAuKc/aJUBQG Ll2NX3VvQ/eLZVxDrkW7eMu5FOuL/N1Y/Ix1Cl2/SZCOdVJxqGsMcSMewRVJJPxmhUCCwZ as/QrLCY5AsArh8HRu44ktKBxBIX/Ic= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1748599499; 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=JBPpoXRrGXk2+QAUGnfzfHq6wXrCHCzvYZZhParVV0Q=; b=ImSv1a5mnHe/xD3ZuGKvoHPRy9S6CxNNnPw9w59F4S8LMeGQt7L9tZylWTS6vgEppl0NCY UFY1lAq0mybQMsqcHUuvFscvKpNxBec1BL4SR7wR1xVyZCyi+JFXoBq+v9ZQ8XeVyZnKuU EA88IprVPE0wg5PvrTCHPolJvdgSbnk= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-449-eQsJMhWaP0q1wedDl9IZRg-1; Fri, 30 May 2025 06:04:57 -0400 X-MC-Unique: eQsJMhWaP0q1wedDl9IZRg-1 X-Mimecast-MFC-AGG-ID: eQsJMhWaP0q1wedDl9IZRg_1748599497 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-43efa869b19so15317485e9.2 for ; Fri, 30 May 2025 03:04:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1748599496; x=1749204296; 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=JBPpoXRrGXk2+QAUGnfzfHq6wXrCHCzvYZZhParVV0Q=; b=p8nIRbaYxM1kT6JrCz7qnsI/Jg7jnkjBTtyb7B7OIWIpDqnOM+hDDD7CWuvC3F4ILM RwnG9y7NQoRGPqeMqgyrLYwrBRJ+zJfWpC+xif7ze0ucuDl3RWuCzJH4Lo7JH4XXk1E1 KwFB4/sQsWg+f8zQxRUXshEVP2ZBek8PMuUVJVmBjZzl1LMfWMJ38K020W8BYDGsf341 Fnce5o8K2zcHQXYLutCry6qGTSxEXMjLqOiDsa/H1hbJ1/gTd6VKejjmCi5tXUHRDv2T xU6J9eGRPxH8oZfey7gPParsrhG9o/M/Nzl6a10fgY3agyt2/1JOedVBv/6MraHX9moa F8kg== X-Forwarded-Encrypted: i=1; AJvYcCUlkin86RgUJINXYkvsm673r5zF6iW5R10NQUBgUXSSz+t0Vnma/xik5Ex5MaXb6/UzYAL1VC++dQ==@kvack.org X-Gm-Message-State: AOJu0Yy/WtmXollXPmCZ6F1q3QUORtlVYcPUuW4dhuzFCmDZ4SwKcoqk kwErjOOrZcndhX/8TDv7cOVBAIRE5bC7FxFzJo0N1N3rKGFHKe7Qedgq74a7bB1GUHLGiNp4gJr IcQ49rfkxvrQhAr2G+cxux/XfPR1HLpIkZ4oenCeJMHvkiVqFe5QI X-Gm-Gg: ASbGncuWHgjbVbb7W60gcPb7kXeePf4Nm81DYJjnShQFfRwq7YTPleYBlUfS+AWFQQU ncQMaBakh+2kGEZ9aFCY9+shMfb0Y/n+wiN/Wg2jsZSNIts+FgwKsfGfElnHzb1BVhkY28OL2Q5 4rTKVm4EJjuzrYDO3zXkC0WaLqLCXVw09eYl8aLxkVPaEITM1yguCQrTZnulJIrtoTx6QHnMccL nec/ezNmwAYOWpNZbN0FDkrIdF4lZWIWznlNcsq6A8Jqv/okEOisfcMYfE4jp+ZK8EeKHHZ5jLI 6ISgPgRsUsEL4T07AXlszpJymKzNPZQbF7en0a0VVD7O0dbuLCtdxaOkYu1K96XGV5NK05HBPhc NNvDnLt2lCCQRMqsE/kdiPSU+N8vXyvt1trzH6uI= X-Received: by 2002:a05:600c:3b10:b0:44a:b478:1387 with SMTP id 5b1f17b1804b1-450d885e485mr15965615e9.17.1748599496590; Fri, 30 May 2025 03:04:56 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFqBx26DpmQBqu+8Z8GVxyJYhddzjEfiVq3NfFD+pe72mCQP/nUsskQFM9pqT8nH+SXQAd/gw== X-Received: by 2002:a05:600c:3b10:b0:44a:b478:1387 with SMTP id 5b1f17b1804b1-450d885e485mr15965035e9.17.1748599496104; Fri, 30 May 2025 03:04:56 -0700 (PDT) Received: from ?IPV6:2003:d8:2f03:5b00:f549:a879:b2d3:73ee? (p200300d82f035b00f549a879b2d373ee.dip0.t-ipconnect.de. [2003:d8:2f03:5b00:f549:a879:b2d3:73ee]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-450d7fa23f4sm13792685e9.14.2025.05.30.03.04.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 May 2025 03:04:55 -0700 (PDT) Message-ID: Date: Fri, 30 May 2025 12:04:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix COW mapping handing in generic_access_phys To: Jason Gunthorpe Cc: Peter Xu , Jinjiang Tu , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, wangkefeng.wang@huawei.com References: <5b9f5952-9979-426f-857a-dffa9b7963af@redhat.com> <20250528162915.GR61950@nvidia.com> <8b307f83-6a16-46c1-b71b-64af9ca0f592@redhat.com> <20250528174754.GA61950@nvidia.com> <84a19161-765d-4aba-b42f-5fdd8c986bdf@redhat.com> <20250528181506.GA192531@nvidia.com> <331096ae-e648-4a6e-8728-5cc0bf319b3b@redhat.com> <20250528182936.GB192531@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 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: <20250528182936.GB192531@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 5hPRkR9LV9JnLU9IpcjppIPdz--jWBaEa0CEqrZZMig_1748599497 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: rspam03 X-Rspamd-Queue-Id: A003A18000E X-Stat-Signature: ih6bdij7gz8h5snp1ik7bt6mzocufs6n X-Rspam-User: X-HE-Tag: 1748599499-312722 X-HE-Meta: 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 l/Zyu68p YXAn1Ur4YJCZvSuAD222Lq/CVjWuKmQxRxurDroRx72+/wVo1gE+VPl70GethPLtIdQOM0pYhxoMTolkvq7fBV2nqzJcIcTMBVCyJihRR8oi06JsPIhZy1o0XOPWz0ZGNBGkKiLpGmA+Y7AjOL7elpAoOIHesSMhV9dkc2DGyJhU2segy/mN+70cQJFkSrod7h4FqKpaxDbFrp4OvYTFODarOnxCbAYX1wYEKtaZRmyYjHOFoXMk9fEou4SbAPkA8J07J3lTjF2nG2ndXZimRKGMbz4ecKyX1E1dLQ7D22U0pn9fPkaTtZ3mAcHFArJXbCyQCGnRxc/ic/yXvuKn9x3pIqYXjAWOLeOujUZa/4BqvI2Q4wRhapyRWyEJ0CbuRUO0dkIjwNZio4m6qzwEmMPFF5RfbqiDh/nme/+KehZ2pPYDNv4WrrR/l5BdTxzPwQTRoVgTVxo2AWsA= 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 20:29, Jason Gunthorpe wrote: > On Wed, May 28, 2025 at 08:22:08PM +0200, David Hildenbrand wrote: >> On 28.05.25 20:15, Jason Gunthorpe wrote: >>> On Wed, May 28, 2025 at 08:00:34PM +0200, David Hildenbrand wrote: >>> >>>> Having refcounted anon page in a VM_PFNMAP doesn't suddenly turn the whole >>>> thing into a MIXEDMAP where other things with a "struct page" are suddenly >>>> refcounted as well. >>> >>> The special COW rules for PFNMAP require a single linear mapping so >>> that vma->vm_pgoff can encode the "special" range. >> >> Yes, I have a semi-ugly patch to adjust remove that special casing. >> >> (less ugly than current handling: *still* lookup the struct page, and if it >> references an anonymous folio, we ... have an anonymous folio. Because >> nobody should ever,ever,ever PFNMAP an anonymous folio. Ever.) > > Hmm, maybe so. I'll try to send out a prototype of that patch once I managed to ... finish never ending stream of review :) > >> In remap_pfn_range_internal() we sanity-check that right now. And fail if it >> is not in place. >> >> Any COW VM_PFNMAP that doesn't go through remap_pfn_range() would be ... >> broken. I don't think we have them. > > It is a really easy driver mistake to make though, you have to omit > the rejection of !VM_SHARED, then go on and do something else. As I just reviewed related code, I think when not using remap_pfn_range(), a driver -- like vfio -- will be using vmf_insert_pfn(). There, we sanity check it as well: vmf_insert_pfn()->vmf_insert_pfn_prot() BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); > > How many drivers use VM_PFNMAP without remap_pfn_range() and don't > check for VM_SHARED? Not sure, only a handful even use vmf_insert_pfn(), and the BUG_ON would at least catch it. -- Cheers, David / dhildenb