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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/7/26 05:50, Anshuman Khandual wrote: > Currently vma->vm_page_prot is safely read from and written to, without any > locks with READ_ONCE() and WRITE_ONCE(). But with introduction of D128 page > tables on arm64 platform, vm_page_prot grows to 128 bits which can't safely > be handled with READ_ONCE() and WRITE_ONCE(). > > Add read and write accessors for vm_page_prot like pgprot_[read|write]() > which any platform can override when required, although still defaulting as > READ_ONCE() and WRITE_ONCE(), thus preserving the functionality for others. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: Mike Rapoport > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Acked-by: Mike Rapoport (Microsoft) > Signed-off-by: Anshuman Khandual > --- > include/linux/pgtable.h | 14 ++++++++++++++ > mm/huge_memory.c | 4 ++-- > mm/memory.c | 2 +- > mm/migrate.c | 2 +- > mm/mmap.c | 2 +- > 5 files changed, 19 insertions(+), 5 deletions(-) > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index e3c8ab96941c..0df57a5c19ef 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -524,6 +524,20 @@ static inline pgd_t pgdp_get(pgd_t *pgdp) > } > #endif > > +#ifndef pgprot_read > +static inline pgprot_t pgprot_read(pgprot_t *prot) Try passing "const pgprot_t *prot" instead. [...] > diff --git a/mm/migrate.c b/mm/migrate.c > index 15b45832bcfa..579152cce502 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -387,7 +387,7 @@ static bool remove_migration_pte(struct folio *folio, > > folio_get(folio); > new = folio_page(folio, idx); > - pte = mk_pte(new, READ_ONCE(vma->vm_page_prot)); > + pte = mk_pte(new, pgprot_read(&vma->vm_page_prot)); I do wonder whether a ogprot_t vma_get_page_prot(const struct vm_area_struct *vma) where we hide the pgprot access would be a good complement for vma_set_page_prot(). Just a thought. > diff --git a/mm/mmap.c b/mm/mmap.c > index 4bf26b0f1e6e..729bc244b317 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -89,7 +89,7 @@ void vma_set_page_prot(struct vm_area_struct *vma) > vm_page_prot = vma_pgprot_modify(vm_page_prot, vma_flags); > } > /* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */ > - WRITE_ONCE(vma->vm_page_prot, vm_page_prot); > + pgprot_write(&vma->vm_page_prot, vm_page_prot); > } > > /* -- Cheers, David