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(p200300d82f32c2009add4a7a46aaf740.dip0.t-ipconnect.de. [2003:d8:2f32:c200:9add:4a7a:46aa:f740]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4408d0a7802sm127236275e9.1.2025.04.28.10.12.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Apr 2025 10:12:12 -0700 (PDT) Message-ID: Date: Mon, 28 Apr 2025 19:12:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 03/11] x86/mm/pat: introduce pfnmap_track() and pfnmap_untrack() To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Andrew Morton , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Peter Xu References: <20250425081715.1341199-1-david@redhat.com> <20250425081715.1341199-4-david@redhat.com> <554a6063-268c-49a7-883b-c39cf541c146@lucifer.local> 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: <554a6063-268c-49a7-883b-c39cf541c146@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: K9AGA7Ub0-1EuM1zo9vmwVfglweaZnz6tV7eg3YqHrw_1745860333 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: rspam10 X-Rspamd-Queue-Id: EF23520019 X-Stat-Signature: i57dsykry4fu97uxkjks7tmgbhcsbd5j X-Rspam-User: X-HE-Tag: 1745860339-193337 X-HE-Meta: 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 OZ76qiI6 gh/rf/qhNLitHWOocuho5mg9KMleyyM3+1coB8s613NonZrYWLcNtA+mHdDQN5QA8B3AnSYVAt6raRNveVIKDWBSaWV77X51fpzpI68kY8Sd4QQvMVXArnEhJOAbpL68DhQji72Nr30lvIzwb5QZjIPc86FTeru7vHpzBgQQd8WHcTCEPbiElyJuIeHTeDppd/ya9ubaZJGrla4Van9ZxXmmMrN1N94TFDj6r9ma0jJmR6fs/DE1g6oVVK/T7RKSOE+Wp/HVCOb2rQDvHrkV+71NyeyVelhfl6OkKZZo5PnbcCnrxWqmZz24bN2rYBzOU2wQnsKt7gVK9aL4XgXhZnyj3HMdAh1/B3dUX1FDgStSP1bhsr/hZtbLB+Stq93GUA+byTOjP/LpW/ctBHYXTdQYitqIwH+achYn5q7GRN6LZAzShKfLCVA5mqhmBvPhivo1A6gwRhRgNJuU= 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: >> >> +int pfnmap_track(unsigned long pfn, unsigned long size, pgprot_t *prot) >> +{ >> + const resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT; >> + >> + return reserve_pfn_range(paddr, size, prot, 0); > > Nitty, but a pattern established by Liam which we've followed consistently > in VMA code is to prefix parameters that might be less than obvious, > especially boolean parameters, with a comment naming the parameter, e.g.: > > return reserve_pfn_range(paddr, size, prot, /*strict_prot=*/0); Not sure I like that. But as this parameter goes away patch #8, I'll leave it as is in this patch and not start a bigger discussion on better alternatives (don't use these stupid boolean variables ...) ;) [...] >> + >> +/** >> + * pfnmap_track - track a pfn range > > To risk sounding annoyingly pedantic and giving the kind of review that is > annoying, this really needs to be expanded, I think perhaps this > description is stating the obvious :) > > To me the confusing thing is that the 'generic' sounding pfnmap_track() is > actually PAT-specific, so surely the description should give a brief > overview of PAT here, saying it's applicable on x86-64 etc. etc. > > I'm not sure there's much use in keeping this generic when it clearly is > not at this point? Sorry, is your suggestion to document more PAT stuff or what exactly? As you know, I'm a busy man ... so instructions/suggestions please :) > >> + * @pfn: the start of the pfn range >> + * @size: the size of the pfn range > > In what units? Given it's a pfn range it's a bit ambiguous as to whether it > should be expressed in pages/bytes. Agreed. It's bytes. (not my favorite here, but good enough) -- Cheers, David / dhildenb