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(p200300d82f42b000db8b7655f60f812b.dip0.t-ipconnect.de. [2003:d8:2f42:b000:db8b:7655:f60f:812b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45e04cf2870sm10194895e9.1.2025.09.11.06.09.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Sep 2025 06:09:25 -0700 (PDT) Message-ID: <9bcaf3ec-c0a1-4ca5-87aa-f84e297d1e42@redhat.com> Date: Thu, 11 Sep 2025 15:09:22 +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 v11 1/5] mm: softdirty: Add pgtable_soft_dirty_supported() 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: <20250911095602.1130290-1-zhangchunyan@iscas.ac.cn> <20250911095602.1130290-2-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: <20250911095602.1130290-2-zhangchunyan@iscas.ac.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11.09.25 11:55, Chunyan Zhang wrote: > Some platforms can customize the PTE PMD entry soft-dirty bit making it > unavailable even if the architecture provides the resource. > > Add an API which architectures can define their specific implementations > to detect if soft-dirty bit is available on which device the kernel is > running. Thinking to myself: maybe pgtable_supports_soft_dirty() would read better Whatever you prefer. > > Signed-off-by: Chunyan Zhang > --- > fs/proc/task_mmu.c | 17 ++++++++++++++++- > include/linux/pgtable.h | 12 ++++++++++++ > mm/debug_vm_pgtable.c | 10 +++++----- > mm/huge_memory.c | 13 +++++++------ > mm/internal.h | 2 +- > mm/mremap.c | 13 +++++++------ > mm/userfaultfd.c | 10 ++++------ > 7 files changed, 52 insertions(+), 25 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 29cca0e6d0ff..9e8083b6d4cd 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 soft-dirty bit is > + * unavailable on which the kernel is running, even if the architecture > + * provides the resource and soft-dirty is compiled in. > + */ > +#ifdef CONFIG_MEM_SOFT_DIRTY > + if (!pgtable_soft_dirty_supported()) > + mnemonics[ilog2(VM_SOFTDIRTY)][0] = 0; > +#endif You can now drop the ifdef. But, I wonder if could we instead just stop setting the flag. Then we don't have to worry about any VM_SOFTDIRTY checks. Something like the following diff --git a/include/linux/mm.h b/include/linux/mm.h index 892fe5dbf9de0..8b8bf63a32ef7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -783,6 +783,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) static inline void vm_flags_init(struct vm_area_struct *vma, vm_flags_t flags) { + VM_WARN_ON_ONCE(!pgtable_soft_dirty_supported() && (flags & VM_SOFTDIRTY)); ACCESS_PRIVATE(vma, __vm_flags) = flags; } @@ -801,6 +802,7 @@ static inline void vm_flags_reset(struct vm_area_struct *vma, static inline void vm_flags_reset_once(struct vm_area_struct *vma, vm_flags_t flags) { + VM_WARN_ON_ONCE(!pgtable_soft_dirty_supported() && (flags & VM_SOFTDIRTY)); vma_assert_write_locked(vma); WRITE_ONCE(ACCESS_PRIVATE(vma, __vm_flags), flags); } @@ -808,6 +810,7 @@ static inline void vm_flags_reset_once(struct vm_area_struct *vma, static inline void vm_flags_set(struct vm_area_struct *vma, vm_flags_t flags) { + VM_WARN_ON_ONCE(!pgtable_soft_dirty_supported() && (flags & VM_SOFTDIRTY)); vma_start_write(vma); ACCESS_PRIVATE(vma, __vm_flags) |= flags; } diff --git a/mm/mmap.c b/mm/mmap.c index 5fd3b80fda1d5..40cb3fbf9a247 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1451,8 +1451,10 @@ static struct vm_area_struct *__install_special_mapping( return ERR_PTR(-ENOMEM); vma_set_range(vma, addr, addr + len, 0); - vm_flags_init(vma, (vm_flags | mm->def_flags | - VM_DONTEXPAND | VM_SOFTDIRTY) & ~VM_LOCKED_MASK); + vm_flags |= mm->def_flags | VM_DONTEXPAND; + if (pgtable_soft_dirty_supported()) + vm_flags |= VM_SOFTDIRTY; + vm_flags_init(vma, vm_flags & ~VM_LOCKED_MASK); vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); vma->vm_ops = ops; diff --git a/mm/vma.c b/mm/vma.c index abe0da33c8446..16a1ed2a6199c 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2551,7 +2551,8 @@ static void __mmap_complete(struct mmap_state *map, struct vm_area_struct *vma) * then new mapped in-place (which must be aimed as * a completely new data area). */ - vm_flags_set(vma, VM_SOFTDIRTY); + if (pgtable_soft_dirty_supported()) + vm_flags_set(vma, VM_SOFTDIRTY); vma_set_page_prot(vma); } @@ -2819,7 +2820,8 @@ int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma, mm->data_vm += len >> PAGE_SHIFT; if (vm_flags & VM_LOCKED) mm->locked_vm += (len >> PAGE_SHIFT); - vm_flags_set(vma, VM_SOFTDIRTY); + if (pgtable_soft_dirty_supported()) + vm_flags_set(vma, VM_SOFTDIRTY); return 0; mas_store_fail: diff --git a/mm/vma_exec.c b/mm/vma_exec.c index 922ee51747a68..c06732a5a620a 100644 --- a/mm/vma_exec.c +++ b/mm/vma_exec.c @@ -107,6 +107,7 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift) int create_init_stack_vma(struct mm_struct *mm, struct vm_area_struct **vmap, unsigned long *top_mem_p) { + unsigned long flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; int err; struct vm_area_struct *vma = vm_area_alloc(mm); @@ -137,7 +138,9 @@ int create_init_stack_vma(struct mm_struct *mm, struct vm_area_struct **vmap, BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); vma->vm_end = STACK_TOP_MAX; vma->vm_start = vma->vm_end - PAGE_SIZE; - vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP); + if (pgtable_soft_dirty_supported()) + flags |= VM_SOFTDIRTY; + vm_flags_init(vma, flags); vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); err = insert_vm_struct(mm, vma); > + > 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 (!pgtable_soft_dirty_supported()) > + 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 (!pgtable_soft_dirty_supported()) > + return; > + > if (pmd_present(pmd)) { > /* See comment in change_huge_pmd() */ > old = pmdp_invalidate(vma, addr, pmdp); That would all be handled with the above never-set-VM_SOFTDIRTY. > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index 4c035637eeb7..2a3578a4ae4c 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -1537,6 +1537,18 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) > #define arch_start_context_switch(prev) do {} while (0) > #endif > > +/* > + * Some platforms can customize the PTE soft-dirty bit making it unavailable > + * even if the architecture provides the resource. > + * Adding this API allows architectures to add their own checks for the > + * devices on which the kernel is running. > + * Note: When overiding it, please make sure the CONFIG_MEM_SOFT_DIRTY > + * is part of this macro. > + */ > +#ifndef pgtable_soft_dirty_supported > +#define pgtable_soft_dirty_supported() IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) > +#endif > + > #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY > #ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION > static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd) > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 830107b6dd08..b32ce2b0b998 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 (!pgtable_soft_dirty_supported()) > return; > > pr_debug("Validating PTE soft dirty\n"); > @@ -702,7 +702,7 @@ static void __init pte_swap_soft_dirty_tests(struct pgtable_debug_args *args) > { > pte_t pte; > > - if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) > + if (!pgtable_soft_dirty_supported()) > return; > > pr_debug("Validating PTE swap soft dirty\n"); > @@ -718,7 +718,7 @@ static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args) > { > pmd_t pmd; > > - if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) > + if (!pgtable_soft_dirty_supported()) > return; > > if (!has_transparent_hugepage()) > @@ -734,8 +734,8 @@ static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) > { > pmd_t pmd; > > - if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) || > - !IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION)) > + if (!pgtable_soft_dirty_supported() || > + !IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION)) > return; > > if (!has_transparent_hugepage()) > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 9c38a95e9f09..218d430a2ec6 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2271,12 +2271,13 @@ static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, > > static pmd_t move_soft_dirty_pmd(pmd_t pmd) > { > -#ifdef CONFIG_MEM_SOFT_DIRTY > - if (unlikely(is_pmd_migration_entry(pmd))) > - pmd = pmd_swp_mksoft_dirty(pmd); > - else if (pmd_present(pmd)) > - pmd = pmd_mksoft_dirty(pmd); > -#endif > + if (pgtable_soft_dirty_supported()) { > + if (unlikely(is_pmd_migration_entry(pmd))) > + pmd = pmd_swp_mksoft_dirty(pmd); > + else if (pmd_present(pmd)) > + pmd = pmd_mksoft_dirty(pmd); > + } > + Wondering, should simply the arch take care of that and we can just clal pmd_swp_mksoft_dirty / pmd_mksoft_dirty? > return pmd; > } > > diff --git a/mm/internal.h b/mm/internal.h > index 45b725c3dc03..c6ca62f8ecf3 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1538,7 +1538,7 @@ static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma) > * VM_SOFTDIRTY is defined as 0x0, then !(vm_flags & VM_SOFTDIRTY) > * will be constantly true. > */ > - if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)) > + if (!pgtable_soft_dirty_supported()) > return false; > That should be handled with the above never-set-VM_SOFTDIRTY. > /* > diff --git a/mm/mremap.c b/mm/mremap.c > index e618a706aff5..7beb3114dbf5 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -162,12 +162,13 @@ static pte_t move_soft_dirty_pte(pte_t pte) > * Set soft dirty bit so we can notice > * in userspace the ptes were moved. > */ > -#ifdef CONFIG_MEM_SOFT_DIRTY > - if (pte_present(pte)) > - pte = pte_mksoft_dirty(pte); > - else if (is_swap_pte(pte)) > - pte = pte_swp_mksoft_dirty(pte); > -#endif > + if (pgtable_soft_dirty_supported()) { > + if (pte_present(pte)) > + pte = pte_mksoft_dirty(pte); > + else if (is_swap_pte(pte)) > + pte = pte_swp_mksoft_dirty(pte); > + } > + > return pte; > } > -- Cheers David / dhildenb