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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id n2-20020a5d4202000000b0032d886039easm12827060wrq.14.2023.11.16.01.36.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Nov 2023 01:36:42 -0800 (PST) Message-ID: <864489b3-5d85-4145-b5bb-5d8a74b9b92d@redhat.com> Date: Thu, 16 Nov 2023 10:36:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V3 PATCH] arm64: mm: swap: save and restore mte tags for large folios To: Barry Song <21cnbao@gmail.com> Cc: steven.price@arm.com, akpm@linux-foundation.org, ryan.roberts@arm.com, catalin.marinas@arm.com, will@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, shy828301@gmail.com, v-songbaohua@oppo.com, wangkefeng.wang@huawei.com, willy@infradead.org, xiang@kernel.org, ying.huang@intel.com, yuzhao@google.com References: <20231114014313.67232-1-v-songbaohua@oppo.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: 8bit X-Rspamd-Queue-Id: 589471C0004 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 6namtffimo7qqfg5a85oobnn9jjha6xs X-HE-Tag: 1700127406-377593 X-HE-Meta: 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 3V/quHL6 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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 15.11.23 21:49, Barry Song wrote: > On Wed, Nov 15, 2023 at 11:16 PM David Hildenbrand wrote: >> >> On 14.11.23 02:43, Barry Song wrote: >>> This patch makes MTE tags saving and restoring support large folios, >>> then we don't need to split them into base pages for swapping out >>> on ARM64 SoCs with MTE. >>> >>> arch_prepare_to_swap() should take folio rather than page as parameter >>> because we support THP swap-out as a whole. >>> >>> Meanwhile, arch_swap_restore() should use page parameter rather than >>> folio as swap-in always works at the granularity of base pages right >>> now. >> >> ... but then we always have order-0 folios and can pass a folio, or what >> am I missing? > > Hi David, > you missed the discussion here: > > https://lore.kernel.org/lkml/CAGsJ_4yXjex8txgEGt7+WMKp4uDQTn-fR06ijv4Ac68MkhjMDw@mail.gmail.com/ > https://lore.kernel.org/lkml/CAGsJ_4xmBAcApyK8NgVQeX_Znp5e8D4fbbhGguOkNzmh1Veocg@mail.gmail.com/ Okay, so you want to handle the refault-from-swapcache case where you get a large folio. I was mislead by your "folio as swap-in always works at the granularity of base pages right now" comment. What you actually wanted to say is "While we always swap in small folios, we might refault large folios from the swapcache, and we only want to restore the tags for the page of the large folio we are faulting on." But, I do if we can't simply restore the tags for the whole thing at once at make the interface page-free? Let me elaborate: IIRC, if we have a large folio in the swapcache, the swap entries/offset are contiguous. If you know you are faulting on page[1] of the folio with a given swap offset, you can calculate the swap offset for page[0] simply by subtracting from the offset. See page_swap_entry() on how we perform this calculation. So you can simply pass the large folio and the swap entry corresponding to the first page of the large folio, and restore all tags at once. So the interface would be arch_prepare_to_swap(struct folio *folio); void arch_swap_restore(struct page *folio, swp_entry_t start_entry); I'm sorry if that was also already discussed. BUT, IIRC in the context of commit cfeed8ffe55b37fa10286aaaa1369da00cb88440 Author: David Hildenbrand Date: Mon Aug 21 18:08:46 2023 +0200 mm/swap: stop using page->private on tail pages for THP_SWAP Patch series "mm/swap: stop using page->private on tail pages for THP_SWAP + cleanups". This series stops using page->private on tail pages for THP_SWAP, replaces folio->private by folio->swap for swapcache folios, and starts using "new_folio" for tail pages that we are splitting to remove the usage of page->private for swapcache handling completely. As long as the folio is in the swapcache, we even do have the proper swp_entry_t start_entry available as folio_swap_entry(folio). But now I am confused when we actually would have to pass "swp_entry_t start_entry". We shouldn't if the folio is in the swapcache ... -- Cheers, David / dhildenb