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[91.12.106.22]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39c301b69c4sm11093637f8f.43.2025.04.07.00.23.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Apr 2025 00:23:07 -0700 (PDT) Message-ID: <630caa8e-2ee2-4895-9e4e-8bf2fa079100@redhat.com> Date: Mon, 7 Apr 2025 09:23:06 +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> 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: 08pix2ki6vncW9d4M9bY5V7ORNQUYXS84h45d49YGAg_1744010589 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: 223E94000A X-Stat-Signature: hkwf3wkrj1gb78i1zwjj8hjbwqyhktke X-HE-Tag: 1744010593-83766 X-HE-Meta: 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 4pCS3b6U YTTwTgRvsCRZNz5TnbhxeJdsS2whOGFzHoE0N83TknqSEpnBTFR/Ilc6rTEbkaPxXqi8wis6ghIU0FW19h4pgVpZHUhUA0ZWTLiVyvBWEZg0RA721tIU/mDBuw7I1mbgTslTuxEkVybwN2VczNJ2OPcz1mFNT704SaavjvzFhGeQs2sv/GFxgxtEhV/qrGlBmrT17+K5aA61bTAcH7eja0Kgk8l53K6wOSExSb6hZqtCHM5PPU6idz6iiWMGBG4goT3t40p3nSKRw907ov0WEq4JE4hdyNOpJjJY6VwzNVBv/yrP/9eB9SiUTOGDGal4iTIyeli9c28sCV8rKB+wC9lexRRBf5To5wz43ytGoj4LQBBlSqcvRXicvK3xOEcmIbUAfVTd8nHCcAhnOa9cqhj773i1zP3ADThD1q7t416ce8cC2Wx0KAZrPMUvUZa+S3T6VqrnC8EZfTZZeZI0VOmr+8C36w1JFITtOw1aZ2LPkwrA9L6oXMWZA0w== 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 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. > > 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; bool is_cow; int ret; -- Cheers, David / dhildenb