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(p200300d82f2c1e001e1e7a32e7986457.dip0.t-ipconnect.de. [2003:d8:2f2c:1e00:1e1e:7a32:e798:6457]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e2446b0sm10338425e9.21.2025.06.11.23.46.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Jun 2025 23:46:21 -0700 (PDT) Message-ID: Date: Thu, 12 Jun 2025 08:46:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn_pud() To: Dan Williams , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, Andrew Morton , Alistair Popple , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Oscar Salvador , stable@vger.kernel.org References: <20250611120654.545963-1-david@redhat.com> <20250611120654.545963-2-david@redhat.com> <684a58bf34666_2491100d7@dwillia2-xfh.jf.intel.com.notmuch> 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: <684a58bf34666_2491100d7@dwillia2-xfh.jf.intel.com.notmuch> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: wo9-eVfz6TOCV3qta6i1IRAEN1OFssMavXyJg5ACtP8_1749710782 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: pz8xz44hkqrqq8czg5ncxzfwezbqyjp1 X-Rspamd-Queue-Id: 691A0140004 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1749710785-979432 X-HE-Meta: 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 5bM95D4f 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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 12.06.25 06:34, Dan Williams wrote: > David Hildenbrand wrote: >> We setup the cache mode but ... don't forward the updated pgprot to >> insert_pfn_pud(). >> >> Only a problem on x86-64 PAT when mapping PFNs using PUDs that >> require a special cachemode. > > This is only a problem if the kernel mapped the pud in advance of userspace > mapping it, right? Good question, PAT code is confusing. What I understood is that drivers like vfio will register the range with the expected cachemode, and then rely on vm_insert_* to fill out the cachemode for them. Peter explained it in the dicussion here [1] how e.g., vfio triggers that early registration. Regarding vfio, I can see that we do in vfio_pci_core_mmap() unconditionally: vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); and probably rely on us querying the actual cachemode to be used later. vfio can map all kinds of different memory types ... [1] https://lkml.kernel.org/r/aBDXr-Qp4z0tS50P@x1.local > > The change looks good. > > Reviewed-by: Dan Williams > > ...but I am struggling with the scenario where this causes problems in > practice, where vm_page_prot is the wrong cachemode. Yeah, it's all confusing. But as long as we don't conclude that pfnmap_setup_cachemode_pfn() can be removed entirely (esp. also from pte / pmd case), this seems to be the right thing to do and was accidental change in the introducing commit. Is it actually stable material? I don't know, but possibly getting cachemodes wrongs sounds ... bad? -- Cheers, David / dhildenb