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[87.161.164.31]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e75223ea15sm2306665f8f.47.2025.09.09.04.42.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Sep 2025 04:42:28 -0700 (PDT) Message-ID: <6b2f12aa-8ed9-476d-a69d-f05ea526f16a@redhat.com> Date: Tue, 9 Sep 2025 13:42:26 +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 , linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: 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 , Chunyan Zhang References: <20250909095611.803898-1-zhangchunyan@iscas.ac.cn> <20250909095611.803898-2-zhangchunyan@iscas.ac.cn> 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: <20250909095611.803898-2-zhangchunyan@iscas.ac.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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. But as we do also have PMD soft-dirty support, I guess we would want to call this something more abstract "pgtable_soft_dirty_available" or "pgtable_soft_dirty_supported" -- Cheers David / dhildenb