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(p200300cbc7082700bdf6739b9f9d862f.dip0.t-ipconnect.de. [2003:cb:c708:2700:bdf6:739b:9f9d:862f]) by smtp.gmail.com with ESMTPSA id r15-20020adfe68f000000b0033af51eafc6sm2538195wrm.104.2024.01.30.00.47.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jan 2024 00:47:34 -0800 (PST) Message-ID: Date: Tue, 30 Jan 2024 09:47:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 3/9] mm/memory: further separate anon and pagecache folio handling in zap_present_pte() To: Ryan Roberts , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Catalin Marinas , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Michael Ellerman , Christophe Leroy , "Naveen N. Rao" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org References: <20240129143221.263763-1-david@redhat.com> <20240129143221.263763-4-david@redhat.com> <40cfb242-ceb0-44c6-afe7-c1744825dc62@arm.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-Server: rspam09 X-Rspamd-Queue-Id: 02BC012001B X-Stat-Signature: nccshjhcfjnz6dgmyp3e396qzp5ec16j X-Rspam-User: X-HE-Tag: 1706604458-837839 X-HE-Meta: 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 r2pdSV4L 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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 30.01.24 09:45, Ryan Roberts wrote: > On 30/01/2024 08:37, David Hildenbrand wrote: >> On 30.01.24 09:31, Ryan Roberts wrote: >>> On 29/01/2024 14:32, David Hildenbrand wrote: >>>> We don't need up-to-date accessed-dirty information for anon folios and can >>>> simply work with the ptent we already have. Also, we know the RSS counter >>>> we want to update. >>>> >>>> We can safely move arch_check_zapped_pte() + tlb_remove_tlb_entry() + >>>> zap_install_uffd_wp_if_needed() after updating the folio and RSS. >>>> >>>> While at it, only call zap_install_uffd_wp_if_needed() if there is even >>>> any chance that pte_install_uffd_wp_if_needed() would do *something*. >>>> That is, just don't bother if uffd-wp does not apply. >>>> >>>> Signed-off-by: David Hildenbrand >>>> --- >>>>   mm/memory.c | 16 +++++++++++----- >>>>   1 file changed, 11 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/mm/memory.c b/mm/memory.c >>>> index 69502cdc0a7d..20bc13ab8db2 100644 >>>> --- a/mm/memory.c >>>> +++ b/mm/memory.c >>>> @@ -1552,12 +1552,9 @@ static inline void zap_present_pte(struct mmu_gather >>>> *tlb, >>>>       folio = page_folio(page); >>>>       if (unlikely(!should_zap_folio(details, folio))) >>>>           return; >>>> -    ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); >>>> -    arch_check_zapped_pte(vma, ptent); >>>> -    tlb_remove_tlb_entry(tlb, pte, addr); >>>> -    zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent); >>>>         if (!folio_test_anon(folio)) { >>>> +        ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); >>>>           if (pte_dirty(ptent)) { >>>>               folio_mark_dirty(folio); >>>>               if (tlb_delay_rmap(tlb)) { >>>> @@ -1567,8 +1564,17 @@ static inline void zap_present_pte(struct mmu_gather >>>> *tlb, >>>>           } >>>>           if (pte_young(ptent) && likely(vma_has_recency(vma))) >>>>               folio_mark_accessed(folio); >>>> +        rss[mm_counter(folio)]--; >>>> +    } else { >>>> +        /* We don't need up-to-date accessed/dirty bits. */ >>>> +        ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); >>>> +        rss[MM_ANONPAGES]--; >>>>       } >>>> -    rss[mm_counter(folio)]--; >>>> +    arch_check_zapped_pte(vma, ptent); >>> >>> Isn't the x86 (only) implementation of this relying on the dirty bit? So doesn't >>> that imply you still need get_and_clear for anon? (And in hindsight I think that >>> logic would apply to the previous patch too?) >> >> x86 uses the encoding !writable && dirty to indicate special shadow stacks. That >> is, the hw dirty bit is set by software (to create that combination), not by >> hardware. >> >> So you don't have to sync against any hw changes of the hw dirty bit. What you >> had in the original PTE you read is sufficient. >> > > Right, got it. In that case: Thanks a lot for paying that much attention during your reviews! Highly appreciated! > > Reviewed-by: Ryan Roberts > > -- Cheers, David / dhildenb