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(p200300cbc7281600e899f836758b6fef.dip0.t-ipconnect.de. [2003:cb:c728:1600:e899:f836:758b:6fef]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4316f570da9sm65099795e9.5.2024.10.21.10.21.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Oct 2024 10:21:48 -0700 (PDT) Message-ID: Date: Mon, 21 Oct 2024 19:21:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] mm: add PTE_MARKER_GUARD PTE marker To: Lorenzo Stoakes Cc: Vlastimil Babka , Andrew Morton , Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , "Paul E . McKenney" , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Chris Zankel , Max Filippov , Arnd Bergmann , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, Shuah Khan , Christian Brauner , linux-kselftest@vger.kernel.org, Sidhartha Kumar , Jeff Xu , Christoph Hellwig , linux-api@vger.kernel.org, John Hubbard References: <081837b697a98c7fa5832542b20f603d49e0b557.1729440856.git.lorenzo.stoakes@oracle.com> <470886d2-9f6f-4486-a935-daea4c5bea09@suse.cz> <434a440a-d6a4-4144-b4fb-8e0d8535f03f@lucifer.local> <4f4e41f1-531c-4686-b44d-dacdf034c241@lucifer.local> <49afa956-21e1-4b3d-9dde-82a6891f2902@redhat.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: 7bit X-Stat-Signature: emzzgn1aouidyemgm73xc5fjo1ipj1cq X-Rspamd-Queue-Id: AC54A1C0006 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1729531305-821988 X-HE-Meta: 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 yxghw69r SW+ES2isRJQcBn5CJCAfUGKKjAivHObpevCSI8+z5VMbkgg6Mu7JPi6PZdjw6hxHBcMgu/qbfEwUVaeWrLSirhixH8aJFmAmkgGL9K4VG2bmfuu033MlS1+6cS/Z1+0VoejEP4nIMEf4SG2nQVzuWo5HKgdjekg1BZUx2RWubvq+OUdh7VfVU6Y2GnQLYXuTHu8D05Kv9yZCtqh5dJWs0o5uoJRjlobQtqmtt0+yvyNc3P4cScAY7Nxuc0/qta98J+w1IzNz6FpO/RfBH8Sdg+K3f/BIzDApcAUN05xJJyuncd4pVp9r1cyrtt102jly+D2bqkRIrmJ5k1L40/10/J4s855M/ukZa6dyKnKigGdlOn8Ewo8o6mwYI26KvEeLWKCn2dUguDnBzw4k+h9qUeaUvs4JnV62QzYrSMgCOw6N6IUPMnkx9lmGHKPewNS9f3xMc 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: >> >>> >>>> >>>>> >>>>> Also the existing logic is that existing markers (HW poison, uffd-simulated HW >>>>> poison, uffd wp marker) are retained and no error raised on MADV_DONTNEED, and >>>>> no error on MADV_FREE either, so it'd be consistent with existing behaviour. >>>> >>>> >>>> HW poison / uffd-simulated HW poison are expected to be zapped: it's just >>>> like a mapped page with HWPOISON. So that is correct. >>> >>> Well, poison is _not_ zapped on MADV_DONTNEED but _is_ on MADV_FREE :) anyway, I >> >> Huh? >> >> madvise_dontneed_single_vma()->zap_page_range_single(details=NULL)->unmap_single_vma(details=NULL) >> ... zap_pte_range() >> >> } else if (is_hwpoison_entry(entry) || >> is_poisoned_swp_entry(entry)) { >> if (!should_zap_cows(details)) >> continue; >> ... >> >> Should just zap them. >> >> What am I missing? > > Yeah ok it's me who's missing something here, I hadn't noticed details == NULL > so should_zap_cows() is true, my mistake! It's confusing code ... I once had a patch to call it "should_zap_anon_folios" etc, but it would only slightly make it clearer what is actually happening. > > In any case we explicitly add code here to prevent guard pages from going. I > will correct everything where I wrongly say otherwise, doh! Right, that's also one of the reasons I don't think "poison" terminology is the best fit, because there are som subtle differences. At least the marker does not mention "poison" but PTE_MARKER_GUARD, which I think is a very good naming :) -- Cheers, David / dhildenb