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(p200300d82f32c2009add4a7a46aaf740.dip0.t-ipconnect.de. [2003:d8:2f32:c200:9add:4a7a:46aa:f740]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a073c8da58sm11505210f8f.15.2025.04.28.07.58.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Apr 2025 07:58:47 -0700 (PDT) Message-ID: <75998f7c-93d2-4b98-bb53-8d858b2c108e@redhat.com> Date: Mon, 28 Apr 2025 16:58:46 +0200 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 02/11] mm: convert track_pfn_insert() to pfnmap_sanitize_pgprot() To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. 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Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato References: <20250425081715.1341199-1-david@redhat.com> <20250425081715.1341199-3-david@redhat.com> <78f88303-6b00-42cf-8977-bf7541fa45a9@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-MFC-PROC-ID: EmaH02fRvH_HF8lDIGtljH_3VlDWmXhfPGOpCnYL2aQ_1745852329 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >> What it does on PAT (only implementation so far ...) is looking up the >> memory type to select the caching mode that can be use. >> >> "sanitize" was IMHO a good fit, because we must make sure that we don't use >> the wrong caching mode. >> >> update/setup/... don't make that quite clear. Any other suggestions? > > I'm very poor on naming.. :( So far anything seems slightly better than > sanitize to me, as the word "sanitize" is actually also used in memtype.c > for other purpose.. see sanitize_phys(). Sure, one can sanitize a lot of things. Here it's the cachemode/pgrpot, in the other functions it's an address. Likely we should just call it pfnmap_X_cachemode()/ Set/update don't really fit for X in case pfnmap_X_cachemode() is a NOP. pfnmap_setup_cachemode() ? Hm. > >> >>> >>>> + * @pfn: the start of the pfn range >>>> + * @size: the size of the pfn range >>>> + * @prot: the pgprot to sanitize >>>> + * >>>> + * Sanitize the given pgprot for a pfn range, for example, adjusting the >>>> + * cachemode. >>>> + * >>>> + * This function cannot fail for a single page, but can fail for multiple >>>> + * pages. >>>> + * >>>> + * Returns 0 on success and -EINVAL on error. >>>> + */ >>>> +int pfnmap_sanitize_pgprot(unsigned long pfn, unsigned long size, >>>> + pgprot_t *prot); >>>> extern int track_pfn_copy(struct vm_area_struct *dst_vma, >>>> struct vm_area_struct *src_vma, unsigned long *pfn); >>>> extern void untrack_pfn_copy(struct vm_area_struct *dst_vma, >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>> index fdcf0a6049b9f..b8ae5e1493315 100644 >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -1455,7 +1455,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write) >>>> return VM_FAULT_OOM; >>>> } >>>> - track_pfn_insert(vma, &pgprot, pfn); >>>> + if (pfnmap_sanitize_pgprot(pfn_t_to_pfn(pfn), PAGE_SIZE, &pgprot)) >>>> + return VM_FAULT_FALLBACK; >>> >>> Would "pgtable" leak if it fails? If it's PAGE_SIZE, IIUC it won't ever >>> trigger, though. >>> >>> Maybe we could have a "void pfnmap_sanitize_pgprot_pfn(&pgprot, pfn)" to >>> replace track_pfn_insert() and never fail? Dropping vma ref is definitely >>> a win already in all cases. >> >> It could be a simple wrapper around pfnmap_sanitize_pgprot(), yes. That's >> certainly helpful for the single-page case. >> >> Regarding never failing here: we should check the whole range. We have to >> make sure that none of the pages has a memory type / caching mode that is >> incompatible with what we setup. > > Would it happen in real world? > > IIUC per-vma registration needs to happen first, which checks for memtype > conflicts in the first place, or reserve_pfn_range() could already have > failed. > > Here it's the fault path looking up the memtype, so I would expect it is > guaranteed all pfns under the same vma is following the verified (and same) > memtype? The whole point of track_pfn_insert() is that it is used when we *don't* use reserve_pfn_range()->track_pfn_remap(), no? track_pfn_remap() would check the whole range that gets mapped, so track_pfn_insert() user must similarly check the whole range that gets mapped. Note that even track_pfn_insert() is already pretty clear on the intended usage: "called when a _new_ single pfn is established" -- Cheers, David / dhildenb