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(p200300d82f3ff800c1015c9f3bc93d08.dip0.t-ipconnect.de. [2003:d8:2f3f:f800:c101:5c9f:3bc9:3d08]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e2a996d7dsm72815125e9.4.2025.09.25.02.53.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 25 Sep 2025 02:53:10 -0700 (PDT) Message-ID: Date: Thu, 25 Sep 2025 11:53:08 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [v6 02/15] mm/huge_memory: add device-private THP support to PMD operations To: Alistair Popple , Balbir Singh Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, damon@lists.linux.dev, dri-devel@lists.freedesktop.org, Matthew Brost , Zi Yan , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Oscar Salvador , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Ralph Campbell , =?UTF-8?Q?Mika_Penttil=C3=A4?= , Francois Dugast References: <20250916122128.2098535-1-balbirs@nvidia.com> <20250916122128.2098535-3-balbirs@nvidia.com> From: David Hildenbrand Content-Language: en-US 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 25.09.25 02:25, Alistair Popple wrote: > On 2025-09-16 at 22:21 +1000, Balbir Singh wrote... >> Extend core huge page management functions to handle device-private THP >> entries. This enables proper handling of large device-private folios in >> fundamental MM operations. >> >> The following functions have been updated: >> >> - copy_huge_pmd(): Handle device-private entries during fork/clone >> - zap_huge_pmd(): Properly free device-private THP during munmap >> - change_huge_pmd(): Support protection changes on device-private THP >> - __pte_offset_map(): Add device-private entry awareness >> >> Signed-off-by: Matthew Brost >> Signed-off-by: Balbir Singh >> Cc: David Hildenbrand >> Cc: Zi Yan >> Cc: Joshua Hahn >> Cc: Rakie Kim >> Cc: Byungchul Park >> Cc: Gregory Price >> Cc: Ying Huang >> Cc: Alistair Popple >> Cc: Oscar Salvador >> Cc: Lorenzo Stoakes >> Cc: Baolin Wang >> Cc: "Liam R. Howlett" >> Cc: Nico Pache >> Cc: Ryan Roberts >> Cc: Dev Jain >> Cc: Barry Song >> Cc: Lyude Paul >> Cc: Danilo Krummrich >> Cc: David Airlie >> Cc: Simona Vetter >> Cc: Ralph Campbell >> Cc: Mika Penttilä >> Cc: Matthew Brost >> Cc: Francois Dugast >> --- >> include/linux/swapops.h | 32 +++++++++++++++++++++++ >> mm/huge_memory.c | 56 ++++++++++++++++++++++++++++++++++------- >> mm/pgtable-generic.c | 2 +- >> 3 files changed, 80 insertions(+), 10 deletions(-) >> >> diff --git a/include/linux/swapops.h b/include/linux/swapops.h >> index 64ea151a7ae3..2687928a8146 100644 >> --- a/include/linux/swapops.h >> +++ b/include/linux/swapops.h >> @@ -594,10 +594,42 @@ static inline int is_pmd_migration_entry(pmd_t pmd) >> } >> #endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ >> >> +#if defined(CONFIG_ZONE_DEVICE) && defined(CONFIG_ARCH_ENABLE_THP_MIGRATION) >> + >> +/** >> + * is_pmd_device_private_entry() - Check if PMD contains a device private swap entry >> + * @pmd: The PMD to check >> + * >> + * Returns true if the PMD contains a swap entry that represents a device private >> + * page mapping. This is used for zone device private pages that have been >> + * swapped out but still need special handling during various memory management >> + * operations. >> + * >> + * Return: 1 if PMD contains device private entry, 0 otherwise >> + */ >> +static inline int is_pmd_device_private_entry(pmd_t pmd) >> +{ >> + return is_swap_pmd(pmd) && is_device_private_entry(pmd_to_swp_entry(pmd)); >> +} >> + >> +#else /* CONFIG_ZONE_DEVICE && CONFIG_ARCH_ENABLE_THP_MIGRATION */ >> + >> +static inline int is_pmd_device_private_entry(pmd_t pmd) >> +{ >> + return 0; >> +} >> + >> +#endif /* CONFIG_ZONE_DEVICE && CONFIG_ARCH_ENABLE_THP_MIGRATION */ >> + >> static inline int non_swap_entry(swp_entry_t entry) >> { >> return swp_type(entry) >= MAX_SWAPFILES; >> } >> >> +static inline int is_pmd_non_present_folio_entry(pmd_t pmd) > > I can't think of a better name either although I am curious why open-coding it > was so nasty given we don't have the equivalent for pte entries. Will go read > the previous discussion. I think for PTEs we just handle all cases (markers, hwpoison etc) properly, manye not being supported yet on the PMD level. See copy_nonpresent_pte() as an example. We don't even have helpers like is_pte_migration_entry(). >> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c >> index 567e2d084071..0c847cdf4fd3 100644 >> --- a/mm/pgtable-generic.c >> +++ b/mm/pgtable-generic.c >> @@ -290,7 +290,7 @@ pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) >> >> if (pmdvalp) >> *pmdvalp = pmdval; >> - if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval))) >> + if (unlikely(pmd_none(pmdval) || !pmd_present(pmdval))) > > Why isn't is_pmd_non_present_folio_entry() used here? I thought I argued that if (!pmd_present(pmdval))) Should be sufficient here in my last review? We want to detect page tables we can map after all. -- Cheers David / dhildenb