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(p200300d82f179c00d650ab5f74c22175.dip0.t-ipconnect.de. [2003:d8:2f17:9c00:d650:ab5f:74c2:2175]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e7521bfe00sm6230360f8f.5.2025.09.10.01.51.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Sep 2025 01:51:11 -0700 (PDT) Message-ID: <8f9a4a13-2881-4baf-ab62-3d0d79e0cd3c@redhat.com> Date: Wed, 10 Sep 2025 10:51:10 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V10 1/5] mm: softdirty: Add pte_soft_dirty_available() To: Chunyan Zhang Cc: Chunyan Zhang , linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Deepak Gupta , Ved Shanbhogue , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Peter Xu , Arnd Bergmann , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Axel Rasmussen , Yuanchu Xie References: <20250909095611.803898-1-zhangchunyan@iscas.ac.cn> <20250909095611.803898-2-zhangchunyan@iscas.ac.cn> <6b2f12aa-8ed9-476d-a69d-f05ea526f16a@redhat.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: 7bit On 10.09.25 10:25, Chunyan Zhang wrote: > Hi David, > > On Tue, 9 Sept 2025 at 19:42, David Hildenbrand wrote: >> >> On 09.09.25 11:56, Chunyan Zhang wrote: >>> Some platforms can customize the PTE soft dirty bit and make it unavailable >>> even if the architecture allows providing the PTE resource. >>> >>> Add an API which architectures can define their specific implementations >>> to detect if the PTE soft-dirty bit is available, on which the kernel >>> is running. >>> >>> Signed-off-by: Chunyan Zhang >>> --- >>> fs/proc/task_mmu.c | 17 ++++++++++++++++- >>> include/linux/pgtable.h | 10 ++++++++++ >>> mm/debug_vm_pgtable.c | 9 +++++---- >>> mm/huge_memory.c | 10 ++++++---- >>> mm/internal.h | 2 +- >>> mm/mremap.c | 10 ++++++---- >>> mm/userfaultfd.c | 6 ++++-- >>> 7 files changed, 48 insertions(+), 16 deletions(-) >>> >>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >>> index 29cca0e6d0ff..20a609ec1ba6 100644 >>> --- a/fs/proc/task_mmu.c >>> +++ b/fs/proc/task_mmu.c >>> @@ -1058,7 +1058,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) >>> * -Werror=unterminated-string-initialization warning >>> * with GCC 15 >>> */ >>> - static const char mnemonics[BITS_PER_LONG][3] = { >>> + static char mnemonics[BITS_PER_LONG][3] = { >>> /* >>> * In case if we meet a flag we don't know about. >>> */ >>> @@ -1129,6 +1129,16 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) >>> [ilog2(VM_SEALED)] = "sl", >>> #endif >>> }; >>> +/* >>> + * We should remove the VM_SOFTDIRTY flag if the PTE soft-dirty bit is >>> + * unavailable on which the kernel is running, even if the architecture >>> + * allows providing the PTE resource and soft-dirty is compiled in. >>> + */ >>> +#ifdef CONFIG_MEM_SOFT_DIRTY >>> + if (!pte_soft_dirty_available()) >>> + mnemonics[ilog2(VM_SOFTDIRTY)][0] = 0; >>> +#endif >>> + >>> size_t i; >>> >>> seq_puts(m, "VmFlags: "); >>> @@ -1531,6 +1541,8 @@ static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr, >>> static inline void clear_soft_dirty(struct vm_area_struct *vma, >>> unsigned long addr, pte_t *pte) >>> { >>> + if (!pte_soft_dirty_available()) >>> + return; >>> /* >>> * The soft-dirty tracker uses #PF-s to catch writes >>> * to pages, so write-protect the pte as well. See the >>> @@ -1566,6 +1578,9 @@ static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma, >>> { >>> pmd_t old, pmd = *pmdp; >>> >>> + if (!pte_soft_dirty_available()) >>> + return; >>> + >>> if (pmd_present(pmd)) { >>> /* See comment in change_huge_pmd() */ >>> old = pmdp_invalidate(vma, addr, pmdp); >>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>> index 4c035637eeb7..c0e2a6dc69f4 100644 >>> --- a/include/linux/pgtable.h >>> +++ b/include/linux/pgtable.h >>> @@ -1538,6 +1538,15 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) >>> #endif >>> >>> #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY >>> + >>> +/* >>> + * Some platforms can customize the PTE soft dirty bit and make it unavailable >>> + * even if the architecture allows providing the PTE resource. >>> + */ >>> +#ifndef pte_soft_dirty_available >>> +#define pte_soft_dirty_available() (true) >>> +#endif >>> + >>> #ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION >>> static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd) >>> { >>> @@ -1555,6 +1564,7 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd) >>> } >>> #endif >>> #else /* !CONFIG_HAVE_ARCH_SOFT_DIRTY */ >>> +#define pte_soft_dirty_available() (false) >>> static inline int pte_soft_dirty(pte_t pte) >>> { >>> return 0; >>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c >>> index 830107b6dd08..98ed7e22ccec 100644 >>> --- a/mm/debug_vm_pgtable.c >>> +++ b/mm/debug_vm_pgtable.c >>> @@ -690,7 +690,7 @@ static void __init pte_soft_dirty_tests(struct pgtable_debug_args *args) >>> { >>> pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); >>> >>> - if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) >>> + if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) || !pte_soft_dirty_available()) >> >> I suggest that you instead make pte_soft_dirty_available() be false without CONFIG_MEM_SOFT_DIRTY. >> >> e.g., for the default implementation >> >> define pte_soft_dirty_available() IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) >> >> That way you can avoid some ifefs and cleanup these checks. > > Do you mean something like this: > > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -1538,6 +1538,16 @@ static inline pgprot_t pgprot_modify(pgprot_t > oldprot, pgprot_t newprot) > #endif > > #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY > +#ifndef arch_soft_dirty_available > +#define arch_soft_dirty_available() (true) > +#endif > +#define pgtable_soft_dirty_supported() > (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && arch_soft_dirty_available()) > + > #ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION > static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd) > { > @@ -1555,6 +1565,7 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd) > } > #endif > #else /* !CONFIG_HAVE_ARCH_SOFT_DIRTY */ > +#define pgtable_soft_dirty_supported() (false) Maybe we can simplify to #ifndef pgtable_soft_dirty_supported #define pgtable_soft_dirty_supported() IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) #endif And then just let the arch that overrides this function just make it respect IS_ENABLED(CONFIG_MEM_SOFT_DIRTY). -- Cheers David / dhildenb