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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-453647f29bdsm144717525e9.18.2025.06.24.07.59.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Jun 2025 07:59:13 -0700 (PDT) Message-ID: <8844a429-917e-44df-a884-6704a41a7cc1@redhat.com> Date: Tue, 24 Jun 2025 16:59:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm/ptdump: Take the memory hotplug lock inside ptdump_walk_pgd() To: Anshuman Khandual , linux-mm@kvack.org Cc: dev.jain@arm.com, Catalin Marinas , Will Deacon , Ryan Roberts , Paul Walmsley , Palmer Dabbelt , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org References: <20250620052427.2092093-1-anshuman.khandual@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: <20250620052427.2092093-1-anshuman.khandual@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: GODF-g1QTO4ofymz4LKR4ieJrmEfFMwXSSJG4_iafHU_1750777155 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5206480011 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 1eq4q68onb8a7owfwtfgc5moqt9fhh39 X-HE-Tag: 1750777158-487388 X-HE-Meta: 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 K3ihaniA 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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 20.06.25 07:24, Anshuman Khandual wrote: > Memory hot remove unmaps and tears down various kernel page table regions > as required. The ptdump code can race with concurrent modifications of the > kernel page tables. When leaf entries are modified concurrently, the dump > code may log stale or inconsistent information for a VA range, but this is > otherwise not harmful. > > But when intermediate levels of kernel page table are freed, the dump code > will continue to use memory that has been freed and potentially reallocated > for another purpose. In such cases, the ptdump code may dereference bogus > addresses, leading to a number of potential problems. > > To avoid the above mentioned race condition, platforms such as arm64, riscv > and s390 take memory hotplug lock, while dumping kernel page table via the > sysfs interface /sys/kernel/debug/kernel_page_tables. > > Similar race condition exists while checking for pages that might have been > marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in > turn calls ptdump_check_wx(). Instead of solving this race condition again, > let's just move the memory hotplug lock inside generic ptdump_check_wx() > which will benefit both the scenarios. > > Drop get_online_mems() and put_online_mems() combination from all existing > platform ptdump code paths. Acked-by: David Hildenbrand -- Cheers, David / dhildenb