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Subject[PATCH 2/2] userfaultfd.2: Update on write-protection support
Date
The shmem/hugetlbfs memory types are supported for write-protection
messages very lately. Update the man page to reflect that.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
man2/userfaultfd.2 | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
index 0928a76d2..99aae8b50 100644
--- a/man2/userfaultfd.2
+++ b/man2/userfaultfd.2
@@ -273,13 +273,17 @@ Since Linux 4.11,
userfaultfd can be also used with hugetlbfs and shared memory mappings.
.\"
.SS Userfaultfd write-protect mode (since 5.7)
-Since Linux 5.7, userfaultfd supports write-protect mode.
+Since Linux 5.7, userfaultfd supports write-protect mode for anonymous memory.
The user needs to first check availability of this feature using
.B UFFDIO_API
ioctl against the feature bit
.B UFFD_FEATURE_PAGEFAULT_FLAG_WP
before using this feature.
.PP
+Since Linux 5.19, the write-protection mode was also supported on shmem and hugetlbfs
+memory types. It can be detected with the feature bit
+.BR UFFD_FEATURE_WP_HUGETLBFS_SHMEM .
+.PP
To register with userfaultfd write-protect mode, the user needs to initiate the
.B UFFDIO_REGISTER
ioctl with mode
@@ -330,8 +334,6 @@ ioctl, whose
should have the flag
.B UFFDIO_WRITEPROTECT_MODE_WP
cleared upon the faulted page or range.
-.PP
-Write-protect mode supports only private anonymous memory.
.SS Reading from the userfaultfd structure
Each
.BR read (2)
--
2.32.0
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