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(p200300d82f3c3a00566226b33e5d438e.dip0.t-ipconnect.de. [2003:d8:2f3c:3a00:5662:26b3:3e5d:438e]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5e8e0d732sm4957680f8f.52.2025.07.11.09.18.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Jul 2025 09:18:46 -0700 (PDT) Message-ID: <02146c79-a4de-430f-8357-0608e796fa60@redhat.com> Date: Fri, 11 Jul 2025 18:18:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V1 PATCH mm-hotfixes 1/3] mm: introduce and use {pgd,p4d}_populate_kernel() To: Harry Yoo , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Andrey Ryabinin , Arnd Bergmann , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter Cc: "H . 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V" , x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org References: <20250709131657.5660-1-harry.yoo@oracle.com> <20250709131657.5660-2-harry.yoo@oracle.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: <20250709131657.5660-2-harry.yoo@oracle.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 1_RxeLEgfKysPWZUnXdUgAIYNZRYx1S9fWUeB3IL4uU_1752250727 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: 6F184140015 X-Stat-Signature: 6u4mqbsfxwgig5behjhgpmyhit51yx9s X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1752250731-92399 X-HE-Meta: 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 vhkU0p3+ 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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 09.07.25 15:16, Harry Yoo wrote: > Intrdocue and use {pgd,p4d}_pouplate_kernel() in core MM code when > populating PGD and P4D entries corresponding to the kernel address > space. The main purpose of these helpers is to ensure synchronization of > the kernel portion of the top-level page tables whenever such an entry > is populated. > > Until now, the kernel has relied on each architecture to handle > synchronization of top-level page tables in an ad-hoc manner. > For example, see commit 9b861528a801 ("x86-64, mem: Update all PGDs for > direct mapping and vmemmap mapping changes"). > > However, this approach has proven fragile, as it's easy to forget to > perform the necessary synchronization when introducing new changes. > > To address this, introduce _kernel() varients of the page table s/varients/variants/ > population helpers that invoke architecture-specific hooks to properly > synchronize the page tables. I was expecting to see the sync be done in common code -- such that it cannot be missed :) But it's really just rerouting to the arch code where the sync can be done, correct? -- Cheers, David / dhildenb