From: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
To: linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Deepak Gupta <debug@rivosinc.com>,
Ved Shanbhogue <ved@rivosinc.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Xu <peterx@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
David Hildenbrand <david@redhat.com>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>, Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>,
Chunyan Zhang <zhang.lyra@gmail.com>
Subject: [PATCH V10 2/5] mm: uffd_wp: Add pte_uffd_wp_available()
Date: Tue, 9 Sep 2025 17:56:08 +0800 [thread overview]
Message-ID: <20250909095611.803898-3-zhangchunyan@iscas.ac.cn> (raw)
In-Reply-To: <20250909095611.803898-1-zhangchunyan@iscas.ac.cn>
Some platforms can customize the PTE uffd_wp bit and make it unavailable
even if the architecture allows providing the PTE resource.
This patch adds a macro API which allows architectures to define
their specific ones for checking if the PTE uffd_wp bit is available.
Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
---
fs/userfaultfd.c | 25 +++++++++--------
include/asm-generic/pgtable_uffd.h | 12 ++++++++
include/linux/mm_inline.h | 7 +++++
include/linux/userfaultfd_k.h | 44 +++++++++++++++++++-----------
mm/memory.c | 6 ++--
5 files changed, 65 insertions(+), 29 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..68e5006e5158 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1270,9 +1270,10 @@ 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 (!IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) ||
+ !pte_uffd_wp_available())
+ goto out;
+
vm_flags |= VM_UFFD_WP;
}
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
@@ -1980,14 +1981,16 @@ 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 (!IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP) ||
+ !pte_uffd_wp_available())
+ uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+ if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP) ||
+ !pte_uffd_wp_available()) {
+ 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..abab46bd718b 100644
--- a/include/asm-generic/pgtable_uffd.h
+++ b/include/asm-generic/pgtable_uffd.h
@@ -61,6 +61,18 @@ static inline pmd_t pmd_swp_clear_uffd_wp(pmd_t pmd)
{
return pmd;
}
+#define pte_uffd_wp_available() (false)
+#else
+/*
+ * Some platforms can customize the PTE uffd_wp bit and make it unavailable
+ * even if the architecture allows providing the PTE resource.
+ * It allows architectures to define their APIs to check if the PTE
+ * uffd_wp bit is available on the specific devices.
+ */
+#ifndef pte_uffd_wp_available
+#define pte_uffd_wp_available() (true)
+#endif
+
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
#endif /* _ASM_GENERIC_PGTABLE_UFFD_H */
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 89b518ff097e..4e5a8a265642 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 and make it unavailable
+ * even if the architecture allows providing the PTE resource.
+ */
+ if (!pte_uffd_wp_available())
+ 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..ec4a815286c8 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) ||
+ !pte_uffd_wp_available()) &&
+ (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 (pte_uffd_wp_available())
+ 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 (pte_uffd_wp_available()) {
+ 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 (pte_uffd_wp_available()) {
+ 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..d6c874221433 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) || !pte_uffd_wp_available())
+ 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
next prev parent reply other threads:[~2025-09-09 9:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 9:56 [PATCH V10 0/5] riscv: mm: Add soft-dirty and uffd-wp support Chunyan Zhang
2025-09-09 9:56 ` [PATCH V10 1/5] mm: softdirty: Add pte_soft_dirty_available() Chunyan Zhang
2025-09-09 11:42 ` David Hildenbrand
2025-09-10 8:25 ` Chunyan Zhang
2025-09-10 8:51 ` David Hildenbrand
2025-09-11 2:51 ` Chunyan Zhang
2025-09-09 9:56 ` Chunyan Zhang [this message]
2025-09-09 11:43 ` [PATCH V10 2/5] mm: uffd_wp: Add pte_uffd_wp_available() David Hildenbrand
2025-09-09 9:56 ` [PATCH V10 3/5] riscv: Add RISC-V Svrsw60t59b extension support Chunyan Zhang
2025-09-09 17:12 ` Andrew Jones
2025-09-09 9:56 ` [PATCH V10 4/5] riscv: mm: Add soft-dirty page tracking support Chunyan Zhang
2025-09-09 9:56 ` [PATCH V10 5/5] riscv: mm: Add uffd write-protect support Chunyan Zhang
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