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[2003:d8:2f31:700:3851:c66a:b6b9:3490]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e2522b1sm174366915e9.25.2025.06.17.06.47.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Jun 2025 06:47:10 -0700 (PDT) Message-ID: Date: Tue, 17 Jun 2025 15:47:09 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/3] vfio/type1: optimize vfio_unpin_pages_remote() for large folio To: lizhe.67@bytedance.com Cc: 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: <20250617124218.25727-1-lizhe.67@bytedance.com> From: David Hildenbrand Content-Language: en-US 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: <20250617124218.25727-1-lizhe.67@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.06.25 14:42, lizhe.67@bytedance.com wrote: > On Tue, 17 Jun 2025 11:49:43 +0200, david@redhat.com wrote: > >> On 17.06.25 11:47, lizhe.67@bytedance.com wrote: >>> On Tue, 17 Jun 2025 09:43:56 +0200, david@redhat.com wrote: >>> >>>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >>>>> index e952bf8bdfab..d7653f4c10d5 100644 >>>>> --- a/drivers/vfio/vfio_iommu_type1.c >>>>> +++ b/drivers/vfio/vfio_iommu_type1.c >>>>> @@ -801,16 +801,43 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr, >>>>> return pinned; >>>>> } >>>>> >>>>> +/* Returned number includes the provided current page. */ >>>>> +static inline unsigned long folio_remaining_pages(struct folio *folio, >>>>> + struct page *page, unsigned long max_pages) >>>>> +{ >>>>> + if (!folio_test_large(folio)) >>>>> + return 1; >>>>> + return min_t(unsigned long, max_pages, >>>>> + folio_nr_pages(folio) - folio_page_idx(folio, page)); >>>>> +} >>>> >>>> Note that I think that should go somewhere into mm.h, and also get used >>>> by GUP. So factoring it out from GUP and then using it here. >>> >>> I think I need to separate this out into a distinct patch within the >>> patchset. Is that correct? >> >> Yes, that's what I would do. > > How do you think of this implementation? > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 242b05671502..eb91f99ea973 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2165,6 +2165,23 @@ static inline long folio_nr_pages(const struct folio *folio) > return folio_large_nr_pages(folio); > } > > +/* > + * folio_remaining_pages - Counts the number of pages from a given > + * start page to the end of the folio. > + * > + * @folio: Pointer to folio > + * @start_page: The starting page from which to begin counting. > + * > + * Returned number includes the provided start page. > + * > + * The caller must ensure that @start_page belongs to @folio. > + */ > +static inline unsigned long folio_remaining_pages(struct folio *folio, > + struct page *start_page) > +{ > + return folio_nr_pages(folio) - folio_page_idx(folio, start_page); > +} > + > /* Only hugetlbfs can allocate folios larger than MAX_ORDER */ > #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE > #define MAX_FOLIO_NR_PAGES (1UL << PUD_ORDER) > diff --git a/mm/gup.c b/mm/gup.c > index 15debead5f5b..14ae2e3088b4 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -242,7 +242,7 @@ static inline struct folio *gup_folio_range_next(struct page *start, > > if (folio_test_large(folio)) > nr = min_t(unsigned int, npages - i, > - folio_nr_pages(folio) - folio_page_idx(folio, next)); > + folio_remaining_pages(folio, next)); > > *ntails = nr; > return folio; > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index b2fc5266e3d2..34e85258060c 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -96,7 +96,7 @@ static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long e > return page; > } > > - skip_pages = folio_nr_pages(folio) - folio_page_idx(folio, page); > + skip_pages = folio_remaining_pages(folio, page); > pfn += skip_pages - 1; > continue; > } > --- Guess I would have pulled the "min" in there, but passing something like ULONG_MAX for the page_isolation case also looks rather ugly. -- Cheers, David / dhildenb