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[91.12.110.230]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3749ee4ab0bsm6117604f8f.16.2024.08.31.02.54.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 31 Aug 2024 02:54:26 -0700 (PDT) Message-ID: Date: Sat, 31 Aug 2024 11:54:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC] mm: arm64: advance pte for contpte_ptep_set_access_flags To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-arm-kernel@lists.infradead.org, Barry Song , Ard Biesheuvel , John Hubbard , Mark Rutland , Catalin Marinas , Will Deacon References: <20240831083537.62111-1-21cnbao@gmail.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: <20240831083537.62111-1-21cnbao@gmail.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: 7bit X-Stat-Signature: qis37ca6duwadcomza1saj6arxciegg8 X-Rspamd-Queue-Id: BB275140013 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1725098071-203628 X-HE-Meta: U2FsdGVkX1/ulAHNycUYlW1W6HlFeOL6CY6tm2bFBuoqgpa8McDaExqicTVudKIEY/RuMcenUkgQ1hvzDbi5xoGzqIJkZhk76RYVeRlFzs61hGkHMWJ3XFNgvwbPB9zykL2eo40iMKVbpU/IAgYTUvniGSCCHNDgkxHK6yq8xR56/NkenH13xrYmzUJTckPgu5P/7LKAGfrlebti7HWFUu7CHaWHlZWcbtA67AxJAOsV5475OrFe6C4SKG8O51G9xLg0QgXc2Nqh09bEQfM6XumVLBbdyjy+8728s4BpH1CUP6EuwV2UMEg4RRcvKquvQsRbUhJJrQ93ajwOUsiUl/x5rBNURRdCeLhY31V6/5oAsmMdbezkq8lXVk1IAgKfIx5eTPWoHR19Ghr6fMd+o0OSlEN/TG5qe0piTTbODO7bNffigNVqYHzXC983cSdDDjbyHMXGvIt0O+HYLweY+D1CXeZxOdi+X9ydpVahsSY6Q4xmlYk/zRgi06agRo8HnX9vlGDO5Ky6IvXLkSdml25t6NnZXtPPaVU40LFM0zZCkcELyJevzaNRCxVU3gbV/+qDTKS+NY5jc2ncWB3NZkRMbo06wsf0AbRpEIfJIth+lHivvsxDUQzt1a5oyjogT8jCUFPwHKudnCLvmV6loffepbGDNKQK9KiLVezTG4O9SqTAmO6H4XzCYZk5Q3dtQcEXBL65bteG52+bayYR08a3/+Cd+9unY1bRxTu9TgMT7BCYFnePgbUcmxyZU91XQad1CHa1UcmDMk3NB7qj3Z7YWrqvZnozPok2A+X3WiT3AHJnvU6zTA6A3YLD4TKwRlJ4cpYgyD9gKGESnl8m4iGPTVf/y+8OqbFyI8z9dlNnKcOmyEhAAvlFNphFl8fXGGOL5SlNvLcQlZ68dj8P8dJLvxmarMoxIIuJaPQbOYxEow2H7dEKm9XdY429EE3wpUWAEIdEvcNSHDEOhvL L8Nv35qm upCZ6IwYg1Y1MTTpLDVVpBTpjN7G8970+IVnqc2Qqs+NxFAx9BP2kCG+jOh7BYYZY8NIuV+CujLkMyk9a/TNTbFTtr8RyJBpvGgfyrc9vjii/3pqvKQlgwnbGhiHWos4ZkMVIHnRCpIHj6VG4mG7R+8xVeL9R8rXd2xCMAHoNwmPKUo5QROFDfbbPW3gDmyhTjXR0UVk+OOa7ijl/UXEgXSrFfR4CJUksHinvd3/N0PHMrVGi0i9Nv+l5NDh/d9DOsXrMTXLunXkFznKnf+sqENh9NKadifvdNno4IRmYq42zv6PWdrPSnhz+mc2vWXxohBlUlGbJyTbglqazQWOYboQNprbZV8GP1J9PNu2h3eZdaK/XRsPuK8swY2WGG1mC8qK99BujuAPduMz7qA0kjqPuz6V2KuYiGExsjPA1WLsoDucDw6XAMibbad5NNFg9KyZTf0gDSnuAJVvMGj4GW17pRYpTUC5tdfG6ct+6M+0JEyQLL7oDWvG8+Olh+u8YiujNzxJzLaXLHLfxleqq3mH+i1dzzfJN1WIds6lwbkat5q1gIVz6JR4qqyobYFMUCVjwfZPHKohi8lNMDeeAdxU6b6Yhq5T6OehFEefISXlVztA= 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 31.08.24 10:35, Barry Song wrote: > From: Barry Song > > Hi Ryan, David, > it seems contpte_ptep_set_access_flags() has never advanced > pte pfn, and it is setting all entries' pfn to the first > subpage. But I feel quite strange we never have a bug reported. > Am I missing something? > > Fixes: 4602e5757bcc ("arm64/mm: wire up PTE_CONT for user mappings") > Cc: Ard Biesheuvel > Cc: John Hubbard > Cc: Mark Rutland > Cc: Catalin Marinas > Cc: David Hildenbrand > Cc: Will Deacon > Signed-off-by: Barry Song > --- > arch/arm64/mm/contpte.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > index a3edced29ac1..10dcd2641184 100644 > --- a/arch/arm64/mm/contpte.c > +++ b/arch/arm64/mm/contpte.c > @@ -421,8 +421,10 @@ int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > ptep = contpte_align_down(ptep); > start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); > > - for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) > + for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) { > __ptep_set_access_flags(vma, addr, ptep, entry, 0); > + entry = pte_advance_pfn(entry, 1); > + } > > if (dirty) > __flush_tlb_range(vma, start_addr, addr, Taking a closer look at __ptep_set_access_flags(), there is: /* only preserve the access flags and write permission * pte_val(entry) &= PTE_RDONLY | PTE_AF | PTE_WRITE | PTE_DIRTY; So it looks like it doesn't need the PFN? OTOH, there is the initial: if (pte_same(pte, entry)) return 0; check that might accelerate things. So unless I am missing something, this works as expected? (and if the pte_same() would frequently be taken with your change would be worthwile to optimize) -- Cheers, David / dhildenb