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 3E8CEC36010 for ; Mon, 7 Apr 2025 18:34:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8E5C16B0005; Mon, 7 Apr 2025 14:33:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 895C36B0007; Mon, 7 Apr 2025 14:33:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 70EDF6B0008; Mon, 7 Apr 2025 14:33:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 4D2E26B0005 for ; Mon, 7 Apr 2025 14:33:59 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id ED31B1414E2 for ; Mon, 7 Apr 2025 18:34:00 +0000 (UTC) X-FDA: 83308097040.09.89AAE10 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf09.hostedemail.com (Postfix) with ESMTP id 83EAC140009 for ; Mon, 7 Apr 2025 18:33:58 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=aInde6La; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 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=1744050838; 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=3+09NZkHFq8f3X25M6QS/1Uwvt5iZdFtU0tu/KyOEi4=; b=M202mPFyCAFDTIjweroIDL7ewmRNl/Nb+ByyT1m0lY/GrvafcQKC4h9t/FCu3/6Z6IgBS1 4tsXuNU0s0l/C9b0yXRMmREshFGG/KyPNrbpZCkgakmSi5XgoAImzB4w1UikWGSx392KRR D6pdR8CZmS9DzCXcAxbOLQSv6J8aXdA= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744050838; a=rsa-sha256; cv=none; b=X4IVb/Ipzy5sMCC0UGG5d8D77MhPTR/ltVn+bngtgET4KFSgPbY7OVM+hrGTVQE12an906 ac7nenbxsPuWlcKDjavMUUgygGyVY6vvryM5kbpDA3TE615ewTQ6Z5mO5o8QlWT0e/3WQh 1i0sA1KU5Xdb6am3kbC8b39UTUDSFJA= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=aInde6La; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744050837; 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=3+09NZkHFq8f3X25M6QS/1Uwvt5iZdFtU0tu/KyOEi4=; b=aInde6LaRgnnKcVSuBQvflWp3Rfar9LQObuYQP/oMJxg0fC4thqH0/7278NwQp662bfSBH 3LXOOmW71zGoyTvycZmTFAgqAzSAmK2/33fIp7lGiDVsqMzuYvBTJ67EpUs26FC707UjVo T7y+bgqnTD+wG1b0oUBBMhGiSal40l4= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-14-LhFcxposMQaHCCz9Bbxm_g-1; Mon, 07 Apr 2025 14:33:56 -0400 X-MC-Unique: LhFcxposMQaHCCz9Bbxm_g-1 X-Mimecast-MFC-AGG-ID: LhFcxposMQaHCCz9Bbxm_g_1744050835 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-43ce245c5acso59278665e9.2 for ; Mon, 07 Apr 2025 11:33:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744050835; x=1744655635; 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=3+09NZkHFq8f3X25M6QS/1Uwvt5iZdFtU0tu/KyOEi4=; b=S3dDF0yr20TYrAp4kdh8GCiTJjsqwIAyt24R63L49+aKXN55ybHU3Wbm7O8LCSI1pL 6N3/UX21yH5szQf1Q1oouIkjN8JKPpa1EmSvsxECzcbyg7D3PA3mqzd9LocYr7d+FhvL AnhSTlMHouLmyOdckBVmwXJ2+OrM4Q06l4Tg4kIedA4pzQ1Sl02mi7dVX/XrJW2nBa9w v3CCPWyTHTzDkW/OCD2thvLCc9bFjY5eivT6Loy2B1dPKDXFBDRheHRIrHFqW7QQt4N+ 9q/XO9R2xKU8hwewdPgimGqXwIMJB9KYPGqUGQwyhsULTC0bjGC+QWDiAUN0Q47LOtkO sfWg== X-Forwarded-Encrypted: i=1; AJvYcCVYm/tEPnM7rOXgtEAls5ZPb363igW+GM7GzQVRLttHcp2zNXxI/KGTjW6/EFVZnRUcCrfHVncGBQ==@kvack.org X-Gm-Message-State: AOJu0YxJEtdxnRgDEWfb2IoChcgKLkK+aVdOAhtPrn27QY6NV/QnpPLZ QkLyfn62m5Duh0VLbwtf+DlDlNpGUKSePE34nbPa8/02niCdc1LrjobiU8gudiYHN83rdx1ip8Z JbxrBnCIwG15RlhYUv2grf57y4RW26VhDX5H6sBiSUU76VP/y X-Gm-Gg: ASbGncsDJa2rR9lB3IBa/p6shkleNRKT9Gx4owhj3oKLSlC9SoXAunkjpkuyCsokbhb PW8ibrjaqdkQskNFKdKR7hnoBFx++pv0rn8v778DJaEr0MEAMDyiVcQXTPIYSf1cREKZDug7BX8 dAEZy1FBUn3eABGkd+HxSwsIVY7vdwbcuE+jO7Jvq55BYDcUtxsFB/9H1eB4lpO5w2zDKCW3mei ZheEeLYDBMxvOBMsi5+VUam6SaMIHhA5vpNfxCfq+Wv9At0u2IqUQRNHM3eQPSLCVklGXrF7Nzs 7EZsyKyrX1JfOhVNgo5o59trEUeROzUatsa7zZU4Jm3PIxJ9idjQO6l9U0kN4acjoDf88UEuRkT nai1/XpjyKG+Xc6rmuLnF4LwKMPoNykRT29x6mZnJL+U= X-Received: by 2002:a05:600c:8711:b0:43d:2230:300f with SMTP id 5b1f17b1804b1-43ed07ad502mr147444895e9.0.1744050835457; Mon, 07 Apr 2025 11:33:55 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFx3M9MnkdUDVlpzDHWjQL1m8tGUcUm4RwESzADjltVHLzy61DWYaNXlYqSwxIrffiWikauaA== X-Received: by 2002:a05:600c:8711:b0:43d:2230:300f with SMTP id 5b1f17b1804b1-43ed07ad502mr147444595e9.0.1744050835015; Mon, 07 Apr 2025 11:33:55 -0700 (PDT) Received: from ?IPV6:2003:cb:c738:3c00:8b01:4fd9:b833:e1e9? (p200300cbc7383c008b014fd9b833e1e9.dip0.t-ipconnect.de. [2003:cb:c738:3c00:8b01:4fd9:b833:e1e9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43ec364a0c7sm137141685e9.29.2025.04.07.11.33.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Apr 2025 11:33:54 -0700 (PDT) Message-ID: <12196206-16b0-4913-b087-1f59ff808603@redhat.com> Date: Mon, 7 Apr 2025 20:33:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] x86/mm/pat: (un)track_pfn_copy() fix + improvements To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, kernel test robot , Dan Carpenter , Andrew Morton , Lorenzo Stoakes , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Rik van Riel , "H. Peter Anvin" , Linus Torvalds References: <20250404124931.2255618-1-david@redhat.com> <630caa8e-2ee2-4895-9e4e-8bf2fa079100@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -KSEKoWJHXaVIVDk48XLEJIIiV03iCio_SfKhf0tCxk_1744050835 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 83EAC140009 X-Stat-Signature: 9ituht3b1happadzsiw1m8q4ma3gcj7k X-HE-Tag: 1744050838-419984 X-HE-Meta: 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 L2poVMFi VqzN/Qltu1+e4RbODv3BPJR/h6AbF7mG2+e/pR2q3eIZXD2bSmFAdyVxCszeHcbNdJc/nZj/gKBXWo74oEpZS522TXkjIw9dAPUv25vpfBofTBQZmLHcxQY+Esz1XkgpqftujZlOOHmV1eo5hkfudBTj5teqtLXSkfqhyHNf3nCakCj+SuaENvdhae79LjcHMk8F36cD8FbHLCTwh1f8XKXk6sbc3YlJswrBqGAUK3CGxgou1pC011fUViTirCcwA6XX5rP04wwbtzdlEldxyjoVmCTtphENKH8r59k4JS6Xtj3TSxmPVaIlQ/RLAWWlE/ZzLtyxi8JpiwpUrA6IWvGGV9ehjBiwynLlbtNjj/HA3GjC33jTwD9lVexo5t6dj3wh/8Vg23cZ+wlFfWEBjavMPVWCi7hFYhp0Ltyw+5H6VcJEuPwkKBLRIZwhQSpgzn0YxNtfHSRTr04NBgYeG0vr7IcM0a0SX7wRy 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 07.04.25 18:50, Ingo Molnar wrote: > > * David Hildenbrand wrote: > >> On 06.04.25 19:28, Ingo Molnar wrote: >>> >>> * David Hildenbrand wrote: >>> >>>> We got a late smatch warning and some additional review feedback. >>>> >>>> smatch warnings: >>>> mm/memory.c:1428 copy_page_range() error: uninitialized symbol 'pfn'. >>> >>>> - if (!(src_vma->vm_flags & VM_PAT)) >>>> + if (!(src_vma->vm_flags & VM_PAT)) { >>>> + *pfn = 0; >>>> return 0; >>>> + } >>> >>>> static inline int track_pfn_copy(struct vm_area_struct *dst_vma, >>>> struct vm_area_struct *src_vma, unsigned long *pfn) >>>> { >>>> + *pfn = 0; >>>> return 0; >>>> } >>> >>> That's way too ugly. There's nothing wrong with not touching 'pfn' >>> in the error path: in fact it's pretty standard API where output >>> pointers may not get set on errors. >> >> We're not concerned about the error path, though. > > Sorry, indeed, not an error path, but the !VM_PAT path above - but > still a similar argument applies IMHO. > >>> If Smatch has a problem with it, Smatch should be fixed, or the false >>> positive warning should be worked around by initializing 'pfn' in the >>> callers. >> >> We could adjust the documentation of track_pfn_copy, to end up with the >> following: >> >> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >> index e2b705c149454..b50447ef1c921 100644 >> --- a/include/linux/pgtable.h >> +++ b/include/linux/pgtable.h >> @@ -1511,8 +1511,9 @@ static inline void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, >> /* >> * track_pfn_copy is called when a VM_PFNMAP VMA is about to get the page >> - * tables copied during copy_page_range(). On success, stores the pfn to be >> - * passed to untrack_pfn_copy(). >> + * tables copied during copy_page_range(). Will store the pfn to be >> + * passed to untrack_pfn_copy() only if there is something to be untracked. >> + * Callers should initialize the pfn to 0. >> */ >> static inline int track_pfn_copy(struct vm_area_struct *dst_vma, >> struct vm_area_struct *src_vma, unsigned long *pfn) >> @@ -1522,7 +1523,9 @@ static inline int track_pfn_copy(struct vm_area_struct *dst_vma, >> /* >> * untrack_pfn_copy is called when a VM_PFNMAP VMA failed to copy during >> - * copy_page_range(), but after track_pfn_copy() was already called. >> + * copy_page_range(), but after track_pfn_copy() was already called. Can >> + * be called even if track_pfn_copy() did not actually track anything: >> + * handled internally. >> */ >> static inline void untrack_pfn_copy(struct vm_area_struct *dst_vma, >> unsigned long pfn) >> diff --git a/mm/memory.c b/mm/memory.c >> index 2d8c265fc7d60..1a35165622e1c 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -1361,7 +1361,7 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) >> struct mm_struct *dst_mm = dst_vma->vm_mm; >> struct mm_struct *src_mm = src_vma->vm_mm; >> struct mmu_notifier_range range; >> - unsigned long next, pfn; >> + unsigned long next, pfn = 0; > > Ack. > > I hate it how uninitialized variables are even a thing in C, and why > there's no compiler switch to turn it off for the kernel. (At least for > non-struct variables. Even for structs I would zero-initialize and > *maybe* allow a non-initialized opt-in for cases where it matters. It > matters in very few cases in praxis. And don't get me started about the > stupidity that is to not initialize holes in struct members ...) > > Over the decades we've lived through numerous nasty bugs for very > little tangible code generation benefits. Ok, let me resend with that. (I'll still tag it as a fix due do the weird UB scenario when passing uninitialized values to a non-inline function ...) -- Cheers, David / dhildenb