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[2003:cb:c718:100:347d:db94:161d:398f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f25915785sm1623471f8f.58.2025.02.13.03.15.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Feb 2025 03:16:00 -0800 (PST) Message-ID: <039b2e48-1d7c-48dc-b832-24db12af216a@redhat.com> Date: Thu, 13 Feb 2025 12:15:58 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 00/17] mm: fixes for device-exclusive entries (hmm) To: Alistair Popple Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, nouveau@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev, Andrew Morton , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jonathan Corbet , Alex Shi , Yanteng Si , Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , SeongJae Park , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pasha Tatashin , Peter Xu , Jason Gunthorpe References: <20250210193801.781278-1-david@redhat.com> <6sejv2hauce3il5lq6sw53xmjjjglxkhz5copm62oryga6jioi@u66wl2nc3hoy> 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: <6sejv2hauce3il5lq6sw53xmjjjglxkhz5copm62oryga6jioi@u66wl2nc3hoy> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: MndkH2jXmh7HOhjAo6VkS2cBYf-IrYiAwITF_g_N-Gw_1739445364 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A94C8180009 X-Stat-Signature: 43776zhbazncynkpwsnxezxo6j6jm9e5 X-HE-Tag: 1739445366-896197 X-HE-Meta: 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 ueZ+VDNu j7VodP5cgT33WungyhJnUcd+24HJF8uF7kGQz/WOMBpWpcQBZsMu1ELSVZCZf41UPJwN74CUX5cEbjqL6xsXSQdYl8iLkZQnbOzYBGTJksi5FnWSAKRBbScmHOJ0BqXREjcDvtIgwuN9s3x+98rne7T1p3/HytP4rlDTqqCSkJC/cRWc1SyKEmRlArVjN75yLZz3IL9VNsXwDXKEBJKZNlYKsP+sZB6Jb8/26bpdXO0Sb0qHJMwVoP6c+Ixjpmvxd+ISjiY9sIbN0OGkPtMK+di0Eqq5y7/HJq/sY3cH0qjM6y0Vu9TAF9TTGgfM0xS9klpZc1TkFDtpPOAU6vvWF1DpWICBn5WicGBK2wZ2bY/Kd2AsYPCZlSDc0qI8tFngJZsbXgIdeE5J6lYxdtxJtjgi5fhf0S4z9tD7Uf3bNRNf7h7mjp/jgpjmIyMu1CAZuomo7+yQoZFoE+5s= 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 13.02.25 12:03, Alistair Popple wrote: > On Mon, Feb 10, 2025 at 08:37:42PM +0100, David Hildenbrand wrote: >> Against mm-hotfixes-stable for now. >> >> Discussing the PageTail() call in make_device_exclusive_range() with >> Willy, I recently discovered [1] that device-exclusive handling does >> not properly work with THP, making the hmm-tests selftests fail if THPs >> are enabled on the system. >> >> Looking into more details, I found that hugetlb is not properly fenced, >> and I realized that something that was bugging me for longer -- how >> device-exclusive entries interact with mapcounts -- completely breaks >> migration/swapout/split/hwpoison handling of these folios while they have >> device-exclusive PTEs. >> >> The program below can be used to allocate 1 GiB worth of pages and >> making them device-exclusive on a kernel with CONFIG_TEST_HMM. >> >> Once they are device-exclusive, these folios cannot get swapped out >> (proc$pid/smaps_rollup will always indicate 1 GiB RSS no matter how >> much one forces memory reclaim), and when having a memory block onlined >> to ZONE_MOVABLE, trying to offline it will loop forever and complain about >> failed migration of a page that should be movable. >> >> # echo offline > /sys/devices/system/memory/memory136/state >> # echo online_movable > /sys/devices/system/memory/memory136/state >> # ./hmm-swap & >> ... wait until everything is device-exclusive >> # echo offline > /sys/devices/system/memory/memory136/state >> [ 285.193431][T14882] page: refcount:2 mapcount:0 mapping:0000000000000000 >> index:0x7f20671f7 pfn:0x442b6a >> [ 285.196618][T14882] memcg:ffff888179298000 >> [ 285.198085][T14882] anon flags: 0x5fff0000002091c(referenced|uptodate| >> dirty|active|owner_2|swapbacked|node=1|zone=3|lastcpupid=0x7ff) >> [ 285.201734][T14882] raw: ... >> [ 285.204464][T14882] raw: ... >> [ 285.207196][T14882] page dumped because: migration failure >> [ 285.209072][T14882] page_owner tracks the page as allocated >> [ 285.210915][T14882] page last allocated via order 0, migratetype >> Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), >> id 14926, tgid 14926 (hmm-swap), ts 254506295376, free_ts 227402023774 >> [ 285.216765][T14882] post_alloc_hook+0x197/0x1b0 >> [ 285.218874][T14882] get_page_from_freelist+0x76e/0x3280 >> [ 285.220864][T14882] __alloc_frozen_pages_noprof+0x38e/0x2740 >> [ 285.223302][T14882] alloc_pages_mpol+0x1fc/0x540 >> [ 285.225130][T14882] folio_alloc_mpol_noprof+0x36/0x340 >> [ 285.227222][T14882] vma_alloc_folio_noprof+0xee/0x1a0 >> [ 285.229074][T14882] __handle_mm_fault+0x2b38/0x56a0 >> [ 285.230822][T14882] handle_mm_fault+0x368/0x9f0 >> ... >> >> This series fixes all issues I found so far. There is no easy way to fix >> without a bigger rework/cleanup. I have a bunch of cleanups on top (some >> previous sent, some the result of the discussion in v1) that I will send >> out separately once this landed and I get to it. >> I wish we could just use some special present PROT_NONE PTEs instead of > > First off David thanks for finding and fixing these issues. If you have further > clean-ups in mind that you need help with please let me know as I'd be happy > to help. Sure! I have some cleanups TBD as result of the previous discussion, but nothing bigger so far. (removing the folio lock could be considered bigger, if we want to go down that path) > >> these (non-present, non-none) fake-swap entries; but that just results in >> the same problem we keep having (lack of spare PTE bits), and staring at >> other similar fake-swap entries, that ship has sailed. >> >> With this series, make_device_exclusive() doesn't actually belong into >> mm/rmap.c anymore, but I'll leave moving that for another day. >> >> I only tested this series with the hmm-tests selftests due to lack of HW, >> so I'd appreciate some testing, especially if the interaction between >> two GPUs wanting a device-exclusive entry works as expected. > > I'm still reviewing the series but so far testing on my single GPU system > appears to be working as expected. I will try and fire up a dual GPU system > tomorrow and test it there as well. Great, thanks a bunch for testing! Out of interest: does the nvidia driver make use of this interface as well, and are you testing with that or with the nouveau driver? I saw some reports that nvidia at least checks for it [1] when building the module: CONFTEST: make_device_exclusive_range [1] https://www.googlecloudcommunity.com/gc/AI-ML/Can-t-Install-Nvidia-Drivers-on-6-1-0-18-Kernel/m-p/722596 -- Cheers, David / dhildenb