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(p200300cbc7277000c050e303f8a76ed9.dip0.t-ipconnect.de. [2003:cb:c727:7000:c050:e303:f8a7:6ed9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-427d68fa394sm118725875e9.3.2024.07.22.02.17.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Jul 2024 02:17:58 -0700 (PDT) Message-ID: <56c982c4-9863-4134-b088-8dfb4b94c531@redhat.com> Date: Mon, 22 Jul 2024 11:17:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/x86/pat: Only untrack the pfn range if unmap region To: Yan Zhao Cc: Peter Xu , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Andrew Morton , Alex Williamson , Jason Gunthorpe , Al Viro , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "Kirill A . Shutemov" , "x86@kernel.org" , "Tian, Kevin" , Pei Li , David Wang <00107082@163.com>, Bert Karwatzki , Sergey Senozhatsky References: <1a0884cb-39ed-455e-a505-7c1b2a0e5225@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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: h3xdgrhyoz71cqbpb3k9q4gr17rdmarw X-Rspamd-Queue-Id: 0D94C40005 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1721639893-661781 X-HE-Meta: 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 zjifZhAl xt6E5Hn9TlnGu+aQEMvTwS8dXrqBEB12/S6tinBTwa2/+h1BDZn31AFy99ZXR4gzSXFFQTBqu8UMDMgbvDFVrM2Ys2Z2XCci3ORin9K/qahj93pYNZOEbmo5FNsQIObwj9mpUmYVWEvfc332nlFZn5/n7sI0Em0qCWZFAwCUBIrP8JETWM1UY+0UQGHvbkDi2TKnRlkiSJrFSE48gi/W3Yw/jwLThrO3Jv9CKK4KGSGg42NXVvkCiOm8XfBmsWdocTr2Sp9nnnIcwkmgdi0JBaudE3Hl7s9bbGqXO0GhT9XhsQZQytgTEPryf//ESSSyMPhLmUc/J8tm4tObOJbNcXCzSvvjfRV60oo8nyU9/aySDl+7Gj6ZUsEhKXXnoSIbEVFzpH62r2cgMZgsRW3ULuRu0Y8/XyOJAmDHGKPUD14c6fKxl7nfLACtvEA== 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 22.07.24 08:43, Yan Zhao wrote: > On Fri, Jul 19, 2024 at 10:28:09AM +0200, David Hildenbrand wrote: >> On 19.07.24 01:18, Yan Zhao wrote: >>> On Thu, Jul 18, 2024 at 10:03:01AM -0400, Peter Xu wrote: >>>> On Thu, Jul 18, 2024 at 09:50:31AM +0800, Yan Zhao wrote: >>>>> Ok. Then if we have two sets of pfns, then we can >>>>> 1. Call remap_pfn_range() in mmap() for pfn set 1. >>>> >>>> I don't think this will work.. At least from the current implementation, >>>> remap_pfn_range() will only reserve the memtype if the range covers the >>>> whole vma. >>> Hmm, by referring to pfn set 1 and pfn set 2, I mean that they're both >>> covering the entire vma, but at different times. >>> >>> To make it more accurately: >>> >>> Consider this hypothetical scenario (not the same as what's implemented in >>> vfio-pci, but seems plausible): >>> >>> Suppose we have a vma covering only one page, then >>> (1) Initially, the vma is mapped to pfn1, with remap_pfn_range(). >>> (2) Subsequently, unmap_single_vma() is invoked to unmap the entire VMA. >>> (3) The driver then maps the entire vma to pfn2 in fault handler >>> >>> Given this context, my questions are: >>> 1. How can we reserve the memory type for pfn2? Should we call >>> track_pfn_remap() in mmap() in advance? >>> 2. How do we untrack the memory type for pfn1 and pfn2, considering they >>> belong to the same VMA but mutual exclusively and not concurrently? >> >> Do we really have to support such changing PFNs in a VMA? Are there existing >> use cases that would rely on that? > I don't know. But it's not disallowed. Okay, but we don't know of any such use case. What we do have is a single VMA, whereby within that VMA we place various different PFN ranges. (randomly looking at drivers/video/fbdev/smscufx.c) These wouldn't have triggered VM_PAT code. -- Cheers, David / dhildenb