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[2003:cb:c707:7600:5c18:5a7d:c5b7:e7a9]) by smtp.gmail.com with ESMTPSA id z20-20020aa785d4000000b006e4c3a6da36sm5546717pfn.202.2024.02.27.02.27.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Feb 2024 02:27:12 -0800 (PST) Message-ID: Date: Tue, 27 Feb 2024 11:27:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] vfio/type1: unpin PageReserved page To: Alex Williamson , Yisheng Xie , akpm@linux-foundation.org Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240226160106.24222-1-ethan.xys@linux.alibaba.com> <20240226091438.1fc37957.alex.williamson@redhat.com> <20240226103238.75ad4b24.alex.williamson@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: <20240226103238.75ad4b24.alex.williamson@redhat.com> 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: 8bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: F2D48140005 X-Stat-Signature: kfhwd5g6zhi8md1wyt3exf5rpqfm4ox8 X-HE-Tag: 1709029637-20440 X-HE-Meta: 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 Al/9lwsv o01dTDV4sTZ78rINHzpyQYsbuQbWSUZMvU7Dh2oGBEMg1bwRDKkUAc6ltmaiqq6ViXWSu/DWrxlQh6SEX9n7X4fUSip4WSNzt9aEKcfBFEONW3eCTUJ8C/0XIdraxrAi9BIipLwR7rYKLCb8oAkapVrtNtl6bRCEZWmtr X-Bogosity: Ham, tests=bogofilter, spamicity=0.000153, 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 26.02.24 18:32, Alex Williamson wrote: > On Tue, 27 Feb 2024 01:14:54 +0800 > Yisheng Xie wrote: > >> 在 2024/2/27 00:14, Alex Williamson 写道: >>> On Tue, 27 Feb 2024 00:01:06 +0800 >>> Yisheng Xie wrote: >>> >>>> We meet a warning as following: >>>> WARNING: CPU: 99 PID: 1766859 at mm/gup.c:209 try_grab_page.part.0+0xe8/0x1b0 >>>> CPU: 99 PID: 1766859 Comm: qemu-kvm Kdump: loaded Tainted: GOE 5.10.134-008.2.x86_64 #1 >>> ^^^^^^^^ >>> >>> Does this issue reproduce on mainline? Thanks, >> >> I have check the code of mainline, the logical seems the same as my >> version. >> >> so I think it can reproduce if i understand correctly. > > I obviously can't speak to what's in your 5.10.134-008.2 kernel, but I > do know there's a very similar issue resolved in v6.0 mainline and > included in v5.10.146 of the stable tree. Please test. Thanks, This commit, to be precise: commit 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4 Author: Alex Williamson Date: Mon Aug 29 21:05:40 2022 -0600 vfio/type1: Unpin zero pages There's currently a reference count leak on the zero page. We increment the reference via pin_user_pages_remote(), but the page is later handled as an invalid/reserved page, therefore it's not accounted against the user and not unpinned by our put_pfn(). Introducing special zero page handling in put_pfn() would resolve the leak, but without accounting of the zero page, a single user could still create enough mappings to generate a reference count overflow. The zero page is always resident, so for our purposes there's no reason to keep it pinned. Therefore, add a loop to walk pages returned from pin_user_pages_remote() and unpin any zero pages. BUT in the meantime, we also have commit c8070b78751955e59b42457b974bea4a4fe00187 Author: David Howells Date: Fri May 26 22:41:40 2023 +0100 mm: Don't pin ZERO_PAGE in pin_user_pages() Make pin_user_pages*() leave a ZERO_PAGE unpinned if it extracts a pointer to it from the page tables and make unpin_user_page*() correspondingly ignore a ZERO_PAGE when unpinning. We don't want to risk overrunning a zero page's refcount as we're only allowed ~2 million pins on it - something that userspace can conceivably trigger. Add a pair of functions to test whether a page or a folio is a ZERO_PAGE. So the unpin_user_page_* won't do anything with the shared zeropage. (likely, we could revert 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4) -- Cheers, David / dhildenb