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Message-Id: <20250915101343.1449546-3-zhangchunyan@iscas.ac.cn>
Date: Mon, 15 Sep 2025 18:13:40 +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 V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()
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 | 22 +++++++++++-----------
include/asm-generic/pgtable_uffd.h | 17 +++++++++++++++++
include/linux/mm_inline.h | 10 ++++++++--
include/linux/userfaultfd_k.h | 27 +++++++++++++--------------
mm/memory.c | 6 ++++--
5 files changed, 53 insertions(+), 29 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..e41736ffa202 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_supports_uffd_wp())
+ goto out;
+
vm_flags |= VM_UFFD_WP;
}
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
@@ -1980,14 +1980,14 @@ 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_supports_uffd_wp())
+ uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+ if (!uffd_supports_wp_marker()) {
+ 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..200da65262a8 100644
--- a/include/asm-generic/pgtable_uffd.h
+++ b/include/asm-generic/pgtable_uffd.h
@@ -1,6 +1,23 @@
#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 overriding it, please make sure the
+ * CONFIG_HAVE_ARCH_USERFAULTFD_WP is part of this macro.
+ */
+#ifndef pgtable_supports_uffd_wp
+#define pgtable_supports_uffd_wp() IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP)
+#endif
+
+static __always_inline bool uffd_supports_wp_marker(void)
+{
+ return pgtable_supports_uffd_wp() && IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP);
+}
+
#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..d6526a7f034b 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -570,9 +570,15 @@ static inline bool
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
bool arm_uffd_pte = false;
+ /*
+ * Some platforms can customize the PTE uffd-wp bit, making it unavailable
+ * even if the architecture allows providing the PTE resource.
+ */
+ if (!uffd_supports_wp_marker())
+ return false;
+
/* The current status of the pte should be "cleared" before calling */
WARN_ON_ONCE(!pte_none(ptep_get(pte)));
@@ -601,7 +607,7 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
make_pte_marker(PTE_MARKER_UFFD_WP));
return true;
}
-#endif
+
return false;
}
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c0e716aec26a..c19435863076 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -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) ||
@@ -436,28 +435,26 @@ 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
+ if (!uffd_supports_wp_marker())
+ return false;
+
return is_pte_marker_entry(entry) &&
- (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
-#else
- return false;
-#endif
+ (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
}
static inline bool pte_marker_uffd_wp(pte_t pte)
{
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
swp_entry_t entry;
+ if (!uffd_supports_wp_marker())
+ return false;
+
if (!is_swap_pte(pte))
return false;
entry = pte_to_swp_entry(pte);
return pte_marker_entry_uffd_wp(entry);
-#else
- return false;
-#endif
}
/*
@@ -466,7 +463,9 @@ 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 (!uffd_supports_wp_marker())
+ return false;
+
if (!is_swap_pte(pte))
return false;
@@ -475,7 +474,7 @@ static inline bool pte_swp_uffd_wp_any(pte_t pte)
if (pte_marker_uffd_wp(pte))
return true;
-#endif
+
return false;
}
diff --git a/mm/memory.c b/mm/memory.c
index 0ba4f6b71847..607e14177412 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 (!uffd_supports_wp_marker())
+ 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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