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@iscas.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;
}
--
2.34.1Hi Chunyan,
kernel test robot noticed the following build errors:
[auto build test ERROR on brauner-vfs/vfs.all]
[also build test ERROR on kees/for-next/execve linus/master v6.17-rc6]
[cannot apply to akpm-mm/mm-everything next-20250915]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Chunyan-Zhang/mm-softdirty-Add-pgtable_supports_soft_dirty/20250915-181826
base: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.all
patch link: https://lore.kernel.org/r/20250915101343.1449546-3-zhangchunyan%40iscas.ac.cn
patch subject: [PATCH V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()
config: riscv-randconfig-002-20250916 (https://download.01.org/0day-ci/archive/20250916/202509161304.mQnxOxhS-lkp@intel.com/config)
compiler: riscv32-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250916/202509161304.mQnxOxhS-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509161304.mQnxOxhS-lkp@intel.com/
All errors (new ones prefixed by >>):
In file included from include/linux/mm_inline.h:10,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:441:9: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
441 | return is_pte_marker_entry(entry) &&
| ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:10: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
442 | (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
| ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:34: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
442 | (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
| ^~~~~~~~~~~~~~~~~~
include/linux/userfaultfd_k.h:442:34: note: each undeclared identifier is reported only once for each function it appears in
include/linux/userfaultfd_k.h: In function 'pte_marker_uffd_wp':
>> include/linux/userfaultfd_k.h:452:7: error: implicit declaration of function 'is_swap_pte'; did you mean 'is_swap_pmd'? [-Werror=implicit-function-declaration]
452 | if (!is_swap_pte(pte))
| ^~~~~~~~~~~
| is_swap_pmd
>> include/linux/userfaultfd_k.h:455:10: error: implicit declaration of function 'pte_to_swp_entry' [-Werror=implicit-function-declaration]
455 | entry = pte_to_swp_entry(pte);
| ^~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:455:10: error: incompatible types when assigning to type 'swp_entry_t' from type 'int'
In file included from include/linux/mm_inline.h:11,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
include/linux/swapops.h: At top level:
>> include/linux/swapops.h:124:19: error: static declaration of 'is_swap_pte' follows non-static declaration
124 | static inline int is_swap_pte(pte_t pte)
| ^~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
include/linux/userfaultfd_k.h:452:7: note: previous implicit declaration of 'is_swap_pte' was here
452 | if (!is_swap_pte(pte))
| ^~~~~~~~~~~
In file included from include/linux/mm_inline.h:11,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
>> include/linux/swapops.h:133:27: error: conflicting types for 'pte_to_swp_entry'
133 | static inline swp_entry_t pte_to_swp_entry(pte_t pte)
| ^~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
include/linux/userfaultfd_k.h:455:10: note: previous implicit declaration of 'pte_to_swp_entry' was here
455 | entry = pte_to_swp_entry(pte);
| ^~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:11,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
>> include/linux/swapops.h:429:20: error: conflicting types for 'is_pte_marker_entry'
429 | static inline bool is_pte_marker_entry(swp_entry_t entry)
| ^~~~~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
include/linux/userfaultfd_k.h:441:9: note: previous implicit declaration of 'is_pte_marker_entry' was here
441 | return is_pte_marker_entry(entry) &&
| ^~~~~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:11,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
>> include/linux/swapops.h:434:26: error: conflicting types for 'pte_marker_get'
434 | static inline pte_marker pte_marker_get(swp_entry_t entry)
| ^~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/internal.h:13,
from mm/page_frag_cache.c:21:
include/linux/userfaultfd_k.h:442:10: note: previous implicit declaration of 'pte_marker_get' was here
442 | (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
| ^~~~~~~~~~~~~~
cc1: some warnings being treated as errors
--
In file included from include/linux/mm_inline.h:10,
from mm/mremap.c:12:
include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:441:9: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
441 | return is_pte_marker_entry(entry) &&
| ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:10: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
442 | (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
| ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:34: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
442 | (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
| ^~~~~~~~~~~~~~~~~~
include/linux/userfaultfd_k.h:442:34: note: each undeclared identifier is reported only once for each function it appears in
include/linux/userfaultfd_k.h: In function 'pte_marker_uffd_wp':
>> include/linux/userfaultfd_k.h:452:7: error: implicit declaration of function 'is_swap_pte'; did you mean 'is_swap_pmd'? [-Werror=implicit-function-declaration]
452 | if (!is_swap_pte(pte))
| ^~~~~~~~~~~
| is_swap_pmd
>> include/linux/userfaultfd_k.h:455:10: error: implicit declaration of function 'pte_to_swp_entry' [-Werror=implicit-function-declaration]
455 | entry = pte_to_swp_entry(pte);
| ^~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:455:10: error: incompatible types when assigning to type 'swp_entry_t' from type 'int'
In file included from include/linux/mm_inline.h:11,
from mm/mremap.c:12:
include/linux/swapops.h: At top level:
>> include/linux/swapops.h:124:19: error: static declaration of 'is_swap_pte' follows non-static declaration
124 | static inline int is_swap_pte(pte_t pte)
| ^~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/mremap.c:12:
include/linux/userfaultfd_k.h:452:7: note: previous implicit declaration of 'is_swap_pte' was here
452 | if (!is_swap_pte(pte))
| ^~~~~~~~~~~
In file included from include/linux/mm_inline.h:11,
from mm/mremap.c:12:
>> include/linux/swapops.h:133:27: error: conflicting types for 'pte_to_swp_entry'
133 | static inline swp_entry_t pte_to_swp_entry(pte_t pte)
| ^~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/mremap.c:12:
include/linux/userfaultfd_k.h:455:10: note: previous implicit declaration of 'pte_to_swp_entry' was here
455 | entry = pte_to_swp_entry(pte);
| ^~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:11,
from mm/mremap.c:12:
>> include/linux/swapops.h:429:20: error: conflicting types for 'is_pte_marker_entry'
429 | static inline bool is_pte_marker_entry(swp_entry_t entry)
| ^~~~~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/mremap.c:12:
include/linux/userfaultfd_k.h:441:9: note: previous implicit declaration of 'is_pte_marker_entry' was here
441 | return is_pte_marker_entry(entry) &&
| ^~~~~~~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:11,
from mm/mremap.c:12:
>> include/linux/swapops.h:434:26: error: conflicting types for 'pte_marker_get'
434 | static inline pte_marker pte_marker_get(swp_entry_t entry)
| ^~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/mremap.c:12:
include/linux/userfaultfd_k.h:442:10: note: previous implicit declaration of 'pte_marker_get' was here
442 | (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
| ^~~~~~~~~~~~~~
In file included from include/linux/mm_inline.h:10,
from mm/mremap.c:12:
include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
include/linux/userfaultfd_k.h:443:1: warning: control reaches end of non-void function [-Wreturn-type]
443 | }
| ^
cc1: some warnings being treated as errors
vim +/is_pte_marker_entry +441 include/linux/userfaultfd_k.h
2bad466cc9d9b4c Peter Xu 2023-03-09 435
1db9dbc2ef05205 Peter Xu 2022-05-12 436 static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
1db9dbc2ef05205 Peter Xu 2022-05-12 437 {
564509f441b4695 Chunyan Zhang 2025-09-15 438 if (!uffd_supports_wp_marker())
564509f441b4695 Chunyan Zhang 2025-09-15 439 return false;
564509f441b4695 Chunyan Zhang 2025-09-15 440
1db9dbc2ef05205 Peter Xu 2022-05-12 @441 return is_pte_marker_entry(entry) &&
1db9dbc2ef05205 Peter Xu 2022-05-12 @442 (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
1db9dbc2ef05205 Peter Xu 2022-05-12 443 }
1db9dbc2ef05205 Peter Xu 2022-05-12 444
1db9dbc2ef05205 Peter Xu 2022-05-12 445 static inline bool pte_marker_uffd_wp(pte_t pte)
1db9dbc2ef05205 Peter Xu 2022-05-12 446 {
1db9dbc2ef05205 Peter Xu 2022-05-12 447 swp_entry_t entry;
1db9dbc2ef05205 Peter Xu 2022-05-12 448
564509f441b4695 Chunyan Zhang 2025-09-15 449 if (!uffd_supports_wp_marker())
564509f441b4695 Chunyan Zhang 2025-09-15 450 return false;
564509f441b4695 Chunyan Zhang 2025-09-15 451
1db9dbc2ef05205 Peter Xu 2022-05-12 @452 if (!is_swap_pte(pte))
1db9dbc2ef05205 Peter Xu 2022-05-12 453 return false;
1db9dbc2ef05205 Peter Xu 2022-05-12 454
1db9dbc2ef05205 Peter Xu 2022-05-12 @455 entry = pte_to_swp_entry(pte);
1db9dbc2ef05205 Peter Xu 2022-05-12 456
1db9dbc2ef05205 Peter Xu 2022-05-12 457 return pte_marker_entry_uffd_wp(entry);
1db9dbc2ef05205 Peter Xu 2022-05-12 458 }
1db9dbc2ef05205 Peter Xu 2022-05-12 459
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Mon, Sep 15, 2025 at 06:13:40PM +0800, Chunyan Zhang wrote: > 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@iscas.ac.cn> According to patchwork CI for riscv, this doesn't build for 32-bit defconfigs or the no-mmu defconfigs.
On 15.09.25 12:13, Chunyan Zhang wrote:
> 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.
>
Similar to my reply to #1, you should probably summarize what you do
regarding ifdef and "No functional change expected".
> Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
> ---
[...]
LGTM, one not below, thanks!
Acked-by: David Hildenbrand <david@redhat.com>
> +/*
> + * 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);
> +}
Likely a simple "inline" should do the trick?
> +
> #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)
> {
--
Cheers
David / dhildenb
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