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mm: userfaultfd: add pgtable_supports_uffd_wp()

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Some platforms can customize the PTE/PMD entry uffd-wp bit making it
unavailable even if the architecture provides the resource.  This patch
adds a macro API pgtable_supports_uffd_wp() that allows architectures to
define their specific implementations to check if the uffd-wp bit is
available on which device the kernel is running.

Also this patch is removing "ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP" and
"ifdef CONFIG_PTE_MARKER_UFFD_WP" in favor of pgtable_supports_uffd_wp()
and uffd_supports_wp_marker() checks respectively that default to
IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) and
"IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) &&
IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP)" if not overridden by the
architecture, no change in behavior is expected.

Link: https://lkml.kernel.org/r/20251113072806.795029-3-zhangchunyan@iscas.ac.cn
Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Jones <ajones@ventanamicro.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Conor Dooley <conor.dooley@microchip.com>
Cc: Conor Dooley <conor@kernel.org>
Cc: Deepak Gupta <debug@rivosinc.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Chunyan Zhang
2025-11-13 15:28:02 +08:00
committed by Andrew Morton
parent 277a1ae387
commit f59c0924d6
5 changed files with 78 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

69
include/linux/userfaultfd_k.h
View File

@@ -228,15 +228,14 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma,
if (wp_async && (vm_flags == VM_UFFD_WP))
return true;
#ifndef CONFIG_PTE_MARKER_UFFD_WP
/*
* If user requested uffd-wp but not enabled pte markers for
* uffd-wp, then shmem & hugetlbfs are not supported but only
* anonymous.
*/
if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
if (!uffd_supports_wp_marker() && (vm_flags & VM_UFFD_WP) &&
!vma_is_anonymous(vma))
return false;
#endif
/* By default, allow any of anon|shmem|hugetlb */
return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
@@ -291,6 +290,43 @@ void userfaultfd_release_new(struct userfaultfd_ctx *ctx);
void userfaultfd_release_all(struct mm_struct *mm,
struct userfaultfd_ctx *ctx);
static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
{
/* Only wr-protect mode uses pte markers */
if (!userfaultfd_wp(vma))
return false;
/* File-based uffd-wp always need markers */
if (!vma_is_anonymous(vma))
return true;
/*
* Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
* enabled (to apply markers on zero pages).
*/
return userfaultfd_wp_unpopulated(vma);
}
/*
* Returns true if this is a swap pte and was uffd-wp wr-protected in either
* forms (pte marker or a normal swap pte), false otherwise.
*/
static inline bool pte_swp_uffd_wp_any(pte_t pte)
{
if (!uffd_supports_wp_marker())
return false;
if (pte_present(pte))
return false;
if (pte_swp_uffd_wp(pte))
return true;
if (pte_is_uffd_wp_marker(pte))
return true;
return false;
}
#else /* CONFIG_USERFAULTFD */
/* mm helpers */
@@ -415,23 +451,9 @@ static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
return false;
}
#endif /* CONFIG_USERFAULTFD */
static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
{
/* Only wr-protect mode uses pte markers */
if (!userfaultfd_wp(vma))
return false;
/* File-based uffd-wp always need markers */
if (!vma_is_anonymous(vma))
return true;
/*
* Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
* enabled (to apply markers on zero pages).
*/
return userfaultfd_wp_unpopulated(vma);
return false;
}
/*
@@ -440,16 +462,7 @@ static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
*/
static inline bool pte_swp_uffd_wp_any(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
if (pte_present(pte))
return false;
if (pte_swp_uffd_wp(pte))
return true;
if (pte_is_uffd_wp_marker(pte))
return true;
#endif
return false;
}
#endif /* CONFIG_USERFAULTFD */
#endif /* _LINUX_USERFAULTFD_K_H */