On Tue, Mar 23, 2021 at 07:19:12PM +0100, Alejandro Colomar (man-pages) wrote:

Hi Peter,

Please see a few more comments below.

Thanks,

Alex

On 3/22/21 11:08 PM, Peter Xu wrote:

quoted

Write-protect mode is supported starting from Linux 5.7.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
  man2/userfaultfd.2 | 104 ++++++++++++++++++++++++++++++++++++++++++++-
  1 file changed, 102 insertions(+), 2 deletions(-)

diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
index 555e37409..8ad4a71b5 100644
--- a/man2/userfaultfd.2
+++ b/man2/userfaultfd.2

@@ -78,6 +78,32 @@ all memory ranges that were registered with the object are unregistered
  and unread events are flushed.
  .\"
  .PP
+Userfaultfd supports two modes of registration:
+.TP
+.BR UFFDIO_REGISTER_MODE_MISSING " (since 4.10)"
+When registered with
+.B UFFDIO_REGISTER_MODE_MISSING
+mode, the userspace will receive a page fault message
+when a missing page is accessed.
+The faulted thread will be stopped from execution until the page fault is
+resolved from the userspace by either an
+.B UFFDIO_COPY
+or an
+.B UFFDIO_ZEROPAGE
+ioctl.
+.TP
+.BR UFFDIO_REGISTER_MODE_WP " (since 5.7)"
+When registered with
+.B UFFDIO_REGISTER_MODE_WP
+mode, the userspace will receive a page fault message
+when a write-protected page is written.
+The faulted thread will be stopped from execution
+until the userspace un-write-protect the page using an

Here you use un-write-protect, but in the other patch you use
write-unprotect.  Please, use a consistent wording if it's the same thing
(if there are other similar things with different wordings in different
pages, please fix them too, but I didn't see more of those). If there's
already a wording for that in any page, please reuse it (I ignore it).

I tried to look for it, and these are the only ones I got that are related:

man4/fd.4:gets the cached drive state (disk changed, write protected et al.)
man4/st.4:The drive is write-protected.
man4/st.4:An attempt was made to write or erase a write-protected tape.
man4/st.4:when the tape in the drive is write-protected.

Unluckily I didn't find the unprotect part.  I think I'll reword it as
"write-unprotect", since "write" should be an adjective-kind prefix.

quoted

+.B UFFDIO_WRITEPROTECT
+ioctl.
+.PP
+Multiple modes can be enabled at the same time for the same memory range.
+.PP
  Since Linux 4.14, userfaultfd page fault message can selectively embed faulting
  thread ID information into the fault message.
  One needs to enable this feature explicitly using the

@@ -144,6 +170,17 @@ single threaded non-cooperative userfaultfd manager implementations.
  .\" and limitations remaining in 4.11
  .\" Maybe it's worth adding a dedicated sub-section...
  .\"
+.PP
+Starting from Linux 5.7, userfaultfd is able to do

The previous paragraph uses "Siince Linux 4.14".  For consistency, please
use that same wording here.

Ok.

Unless Mike speaks out, I'll still keep Mike's a-b as a credit for reviewing,
considering these changes are small.

Thanks,

-- 
Peter Xu