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Message-Id: <20250911095602.1130290-3-zhangchunyan@iscas.ac.cn>
Date: Thu, 11 Sep 2025 17:55:59 +0800
From: Chunyan Zhang <zhangchunyan@...as.ac.cn>
To: linux-riscv@...ts.infradead.org,
linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Alexandre Ghiti <alex@...ti.fr>,
Deepak Gupta <debug@...osinc.com>,
Ved Shanbhogue <ved@...osinc.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Jan Kara <jack@...e.cz>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Xu <peterx@...hat.com>,
Arnd Bergmann <arnd@...db.de>,
David Hildenbrand <david@...hat.com>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Mike Rapoport <rppt@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Michal Hocko <mhocko@...e.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Yuanchu Xie <yuanchu@...gle.com>,
Chunyan Zhang <zhang.lyra@...il.com>
Subject: [PATCH v11 2/5] mm: userfaultfd: Add pgtable_uffd_wp_supported()
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 that allows architectures to define their
specific implementations to check if the uffd-wp bit is available
on which device the kernel is running.
Signed-off-by: Chunyan Zhang <zhangchunyan@...as.ac.cn>
---
fs/userfaultfd.c | 23 ++++++++--------
include/asm-generic/pgtable_uffd.h | 11 ++++++++
include/linux/mm_inline.h | 7 +++++
include/linux/userfaultfd_k.h | 44 +++++++++++++++++++-----------
mm/memory.c | 6 ++--
5 files changed, 62 insertions(+), 29 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..b549c327d7ad 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1270,9 +1270,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
vm_flags |= VM_UFFD_MISSING;
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
- goto out;
-#endif
+ if (!pgtable_uffd_wp_supported())
+ goto out;
+
vm_flags |= VM_UFFD_WP;
}
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
@@ -1980,14 +1980,15 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
uffdio_api.features &=
~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM);
#endif
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
- uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
-#endif
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
- uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
- uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
- uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
-#endif
+ if (!pgtable_uffd_wp_supported())
+ uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+ if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) ||
+ !pgtable_uffd_wp_supported()) {
+ uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
+ uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
+ uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
+ }
ret = -EINVAL;
if (features & ~uffdio_api.features)
diff --git a/include/asm-generic/pgtable_uffd.h b/include/asm-generic/pgtable_uffd.h
index 828966d4c281..895d68ece0e7 100644
--- a/include/asm-generic/pgtable_uffd.h
+++ b/include/asm-generic/pgtable_uffd.h
@@ -1,6 +1,17 @@
#ifndef _ASM_GENERIC_PGTABLE_UFFD_H
#define _ASM_GENERIC_PGTABLE_UFFD_H
+/*
+ * Some platforms can customize the uffd-wp 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_HAVE_ARCH_USERFAULTFD_WP is part of this macro.
+ */
+#ifndef pgtable_uffd_wp_supported
+#define pgtable_uffd_wp_supported() IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP)
+#endif
#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
static __always_inline int pte_uffd_wp(pte_t pte)
{
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 89b518ff097e..38845b8b79ff 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -571,6 +571,13 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
pte_t *pte, pte_t pteval)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
+ /*
+ * Some platforms can customize the PTE uffd-wp bit, making it unavailable
+ * even if the architecture allows providing the PTE resource.
+ */
+ if (!pgtable_uffd_wp_supported())
+ return false;
+
bool arm_uffd_pte = false;
/* The current status of the pte should be "cleared" before calling */
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c0e716aec26a..6264b56ae961 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -228,15 +228,15 @@ 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 ((!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) ||
+ !pgtable_uffd_wp_supported()) &&
+ (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) ||
@@ -437,8 +437,11 @@ static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
- return is_pte_marker_entry(entry) &&
- (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
+ if (pgtable_uffd_wp_supported())
+ return is_pte_marker_entry(entry) &&
+ (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
+ else
+ return false;
#else
return false;
#endif
@@ -447,14 +450,19 @@ static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
static inline bool pte_marker_uffd_wp(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
- swp_entry_t entry;
+ if (pgtable_uffd_wp_supported()) {
+ swp_entry_t entry;
- if (!is_swap_pte(pte))
- return false;
+ if (!is_swap_pte(pte))
+ return false;
- entry = pte_to_swp_entry(pte);
+ entry = pte_to_swp_entry(pte);
+
+ return pte_marker_entry_uffd_wp(entry);
+ } else {
+ return false;
+ }
- return pte_marker_entry_uffd_wp(entry);
#else
return false;
#endif
@@ -467,14 +475,18 @@ static inline bool pte_marker_uffd_wp(pte_t pte)
static inline bool pte_swp_uffd_wp_any(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
- if (!is_swap_pte(pte))
- return false;
+ if (pgtable_uffd_wp_supported()) {
+ if (!is_swap_pte(pte))
+ return false;
- if (pte_swp_uffd_wp(pte))
- return true;
+ if (pte_swp_uffd_wp(pte))
+ return true;
- if (pte_marker_uffd_wp(pte))
- return true;
+ if (pte_marker_uffd_wp(pte))
+ return true;
+ } else {
+ return false;
+ }
#endif
return false;
}
diff --git a/mm/memory.c b/mm/memory.c
index 0ba4f6b71847..4eb05c5f487b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1465,7 +1465,9 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
{
bool was_installed = false;
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+ if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) || !pgtable_uffd_wp_supported())
+ return false;
+
/* Zap on anonymous always means dropping everything */
if (vma_is_anonymous(vma))
return false;
@@ -1482,7 +1484,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
pte++;
addr += PAGE_SIZE;
}
-#endif
+
return was_installed;
}
--
2.34.1
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