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[2003:d8:2f2d:2400:4052:3b5:fff9:4ed0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a568b087a9sm17020666f8f.55.2025.06.18.04.52.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Jun 2025 04:52:38 -0700 (PDT) Message-ID: Date: Wed, 18 Jun 2025 13:52:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] gup: introduce unpin_user_folio_dirty_locked() To: Jason Gunthorpe Cc: lizhe.67@bytedance.com, akpm@linux-foundation.org, alex.williamson@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, peterx@redhat.com References: <20250617152210.GA1552699@ziepe.ca> <20250618062820.8477-1-lizhe.67@bytedance.com> <20250618113626.GK1376515@ziepe.ca> <9c31da33-8579-414a-9b2a-21d7d8049050@redhat.com> <20250618114629.GL1376515@ziepe.ca> 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: <20250618114629.GL1376515@ziepe.ca> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 2Ar1CYX7EbtSkh70jdeNbR2dLk8ELIUvYUIbtm-jrbk_1750247559 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: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: E6F0E180004 X-Stat-Signature: 7deyqmu7a8p8e8ud3gi6kipwdmouwk3b X-HE-Tag: 1750247561-967873 X-HE-Meta: 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 sj3HJhFJ 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 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 18.06.25 13:46, Jason Gunthorpe wrote: > On Wed, Jun 18, 2025 at 01:42:09PM +0200, David Hildenbrand wrote: >> On 18.06.25 13:40, David Hildenbrand wrote: >>> On 18.06.25 13:36, Jason Gunthorpe wrote: >>>> On Wed, Jun 18, 2025 at 02:28:20PM +0800, lizhe.67@bytedance.com wrote: >>>>> On Tue, 17 Jun 2025 12:22:10 -0300, jgg@ziepe.ca wrote: >>>>>> + while (npage) { >>>>>> + long nr_pages = 1; >>>>>> + >>>>>> + if (!is_invalid_reserved_pfn(pfn)) { >>>>>> + struct page *page = pfn_to_page(pfn); >>>>>> + struct folio *folio = page_folio(page); >>>>>> + long folio_pages_num = folio_nr_pages(folio); >>>>>> + >>>>>> + /* >>>>>> + * For a folio, it represents a physically >>>>>> + * contiguous set of bytes, and all of its pages >>>>>> + * share the same invalid/reserved state. >>>>>> + * >>>>>> + * Here, our PFNs are contiguous. Therefore, if we >>>>>> + * detect that the current PFN belongs to a large >>>>>> + * folio, we can batch the operations for the next >>>>>> + * nr_pages PFNs. >>>>>> + */ >>>>>> + if (folio_pages_num > 1) >>>>>> + nr_pages = min_t(long, npage, >>>>>> + folio_pages_num - >>>>>> + folio_page_idx(folio, page)); >>>>>> + >>>>>> + unpin_user_folio_dirty_locked(folio, nr_pages, >>>>>> + dma->prot & IOMMU_WRITE); >>>>> >>>>> Are you suggesting that we should directly call >>>>> unpin_user_page_range_dirty_lock() here (patch 3/3) instead? >>>> >>>> I'm saying you should not have the word 'folio' inside the VFIO. You >>>> accumulate a contiguous range of pfns, by only checking the pfn, and >>>> then call >>>> >>>> unpin_user_page_range_dirty_lock(pfn_to_page(first_pfn)...); >>>> >>>> No need for any of this. vfio should never look at the struct page >>>> except as the last moment to pass the range. >>> >>> Hah, agreed, that's actually simpler and there is no need to factor >>> anything out. >> >> Ah, no, wait, the problem is that we don't know how many pages we can >> supply, because there might be is_invalid_reserved_pfn() in the range ... > > You stop batching when you hit any invalid_reserved_pfn and flush it. > > It still has to check read back and check every PFN to make sure it is > contiguous, checking reserved too is not a problemm. I thought we also wanted to optimize out the is_invalid_reserved_pfn() check for each subpage of a folio. pfn_valid() + pfn_to_page() are not super cheap in some relevant configs IIRC. -- Cheers, David / dhildenb