From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D173438D6A8 for ; Tue, 18 Aug 2026 14:40:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787064038; cv=none; b=LsxXn1NJ22MfPvPUgap3VJnbeHD3eCI27qBZcgGgOmhQeLDTlY0NpEqRPQQOYhbB2AHb4UkLQkK2aJSZgF+Nb9cKXvR7ReNVzidbuffd0/mojjPo6CTfdFihYIAA3AIY5YYf9UOdRzqOF3UXkCQ/oH2K72V9hgo+DoSgaZpOLcg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787064038; c=relaxed/simple; bh=GHH+bxL2xPNsm12t1PJGVw37HfvTkN8vb5RVeDovVsc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hi+XQfhI9y697zWijKqu3QmbjNEgbxDEQUvqXp8m/CbFl9Pd3xz7PcDflGncl++kxJDiI4o+AK1nNsmvi+G7E3eXytyXBD21CiXjwN0RhiD6SPTrSK1kHoMDPef1yV4hZZGSgMCcb/5HaSpntXHoNZI/YzzKbnpGeDbcS5DQdNM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A+L3xNai; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="A+L3xNai" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC9601F000E9; Tue, 18 Aug 2026 14:40:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787064035; bh=P9UqJ0cWMAqLewxt4FiJQdaK8/rUcL8uMobo62GOPdM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=A+L3xNaic+o8mgxR8Q9rxSFb+DQC+7BvLICT5Cm/gRzAsR6J1hyBQfxczjIrVxqui nkWAt0pXXDg3e6aRznzCSR6b3nw6+2shufi9ew9M8NHBNZryAM1OdR3aqFXoNC0dVx X7qi6YCrCbQBYqcfcjERGY0klraT6sN20sE8aycvs0bCA9IzFvW/KiL42RvT+rAvOm 1L/ZMAtJDmoEXFhve1PjCrM1iH91jNJpns+0knS4pByoEskvJGOTf759SiKFeEgsSy Bhe8TCCis2ETJVLOJiSa2p/SbpPeix64rauqnl0wyq40NkFOd/M8HYPezkVq98YWbX kXqMR1ao3U/uQ== Message-ID: <69e8469c-aa7f-4141-be3c-796c9cf11f2f@kernel.org> Date: Tue, 18 Aug 2026 16:40:25 +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: [PATCH v6 02/12] mm: add PMD swap entry detection support To: Usama Arif , Andrew Morton , chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , "Liam R. Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, kernel-team@meta.com References: <20260818131202.494754-1-usama.arif@linux.dev> <20260818131202.494754-3-usama.arif@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: <20260818131202.494754-3-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/18/26 15:09, Usama Arif wrote: > Currently when a PMD-mapped THP is swapped out, the PMD is always > split into HPAGE_PMD_NR PTE-level swap entries. To preserve huge > page information across swap cycles, later patches will install a > single PMD-level swap entry instead. Add the infrastructure to detect > those entries. > > Teach the softleaf layer to recognise PMD swap entries: > pmd_is_swap_entry() detects them and softleaf_is_valid_pmd_entry() > accepts them as a valid non-present type. Because swap entries do not > encode a PFN, make pmd_softleaf_to_folio() warn and return NULL for them > instead of passing the swap offset to softleaf_to_folio(). Clear the > exclusive overlay bit in softleaf_from_pmd() before decoding, matching > how soft_dirty and uffd bits are already stripped. > > Add pmd_swp_mkexclusive(), pmd_swp_exclusive(), and > pmd_swp_clear_exclusive() helpers to each architecture that supports > PMD softleaf entries (x86, arm64, s390, riscv, loongarch, powerpc), > mirroring the existing PTE swap exclusive helpers in each arch's > pgtable.h. Ah, for migration entries we still use a dedicated migratetype. I actually have on my todo list to move to PTE bits as well. (likely the _swp_ part should then be renamed to indicate that this is for softdirty entries, not just swap entries) > Provide generic no-op PMD swap exclusive fallbacks for > architectures without PMD softleaf support, matching the generic PMD > swap soft-dirty fallbacks. No softleaf implies to migration and no swap, so this would work. You should extend mm/debug_vm_pgtable.c in a separate commit to test what pte_swap_exclusive_tests() tests for PMDs. > > Signed-off-by: Usama Arif > --- > arch/arm64/include/asm/pgtable.h | 6 +++++ > arch/loongarch/include/asm/pgtable.h | 19 ++++++++++++++ > arch/powerpc/include/asm/book3s/64/pgtable.h | 17 +++++++++++++ > arch/riscv/include/asm/pgtable.h | 15 +++++++++++ > arch/s390/include/asm/pgtable.h | 17 +++++++++++++ > arch/x86/include/asm/pgtable.h | 17 +++++++++++++ I'm sorry for asking you to compete with Kiryll's series by creating one patch for each architecture that directly jumps at arch maintainers :) [...] > #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY > static inline pte_t pte_swp_mksoft_dirty(pte_t pte) > { > diff --git a/include/linux/leafops.h b/include/linux/leafops.h > index 7c13c58a5e218..4a6c52974b305 100644 > --- a/include/linux/leafops.h > +++ b/include/linux/leafops.h > @@ -102,6 +102,8 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd) > pmd = pmd_swp_clear_soft_dirty(pmd); > if (pmd_swp_uffd(pmd)) > pmd = pmd_swp_clear_uffd(pmd); > + if (pmd_swp_exclusive(pmd)) > + pmd = pmd_swp_clear_exclusive(pmd); Can't we just unconditionally clear these flags? pmd = pmd_swp_clear_uffd(pmd); pmd = pmd_swp_clear_exclusive(pmd); Avoids these rather unnecessary conditionals unless I am missing something. > arch_entry = __pmd_to_swp_entry(pmd); > > /* Temporary until swp_entry_t eliminated. */ > @@ -634,18 +636,30 @@ static inline bool pmd_is_migration_entry(pmd_t pmd) > */ > static inline bool softleaf_is_valid_pmd_entry(softleaf_t entry) > { > - /* Only device private, migration entries valid for PMD. */ > + /* Device private, migration, and swap entries valid for PMD. */ Can we just drop that comment? I mean, it's as clear as it gets in the code immediately below :) > return softleaf_is_device_private(entry) || > - softleaf_is_migration(entry); > + softleaf_is_migration(entry) || > + softleaf_is_swap(entry); > +} > + -- Cheers, David