Re: [PATCH v2 5/6] UFFDIO_REGISTER.2const: Document UFFDIO_REGISTER_MODE_RWP and 1 << _UFFDIO_RWPROTECT

Alejandro Colomar <[email protected]> Thu, 4 Jun 2026 01:46:54 +0200

Newsgroups	org.kernel.vger.linux-man,org.kvack.linux-mm
Message-ID	<aiC84ZUEr3MwWuq5@devuan>

On 2026-05-26T14:41:48+0100, Kiryl Shutsemau wrote:
> Add the new registration mode bit introduced in Linux 7.2:
> 
>   UFFDIO_REGISTER_MODE_RWP   Track every access (read or write) to a
>                              present page in the registered range.
>                              Cannot be combined with
>                              UFFDIO_REGISTER_MODE_WP; both modes share
>                              the same per-PTE marker bit. Anonymous,
>                              shmem, and hugetlbfs ranges are
>                              compatible.
> 
> Also document the matching argp->ioctls bit, 1 << _UFFDIO_RWPROTECT,
> which the kernel reports only when the range was registered with
> UFFDIO_REGISTER_MODE_RWP (which itself requires UFFD_FEATURE_RWP to
> have been negotiated).
> 
> Signed-off-by: Kiryl Shutsemau <[email protected]>
> Acked-by: Mike Rapoport (Microsoft) <[email protected]>

Patch applied; thanks!


Cheers,
Alex

> ---
>  man/man2const/UFFDIO_REGISTER.2const | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/man/man2const/UFFDIO_REGISTER.2const b/man/man2const/UFFDIO_REGISTER.2const
> index 50064c954b81..ded57cf301ad 100644
> --- a/man/man2const/UFFDIO_REGISTER.2const
> +++ b/man/man2const/UFFDIO_REGISTER.2const
> @@ -72,6 +72,20 @@ .SH DESCRIPTION
>  only hugetlbfs ranges are compatible.
>  Since Linux 5.14,
>  compatibility with shmem ranges was added.
> +.TP
> +.BR UFFDIO_REGISTER_MODE_RWP " (since Linux 7.2)"
> +Track page faults on read-write-protected pages.
> +Every access
> +(read or write)
> +to a page present within the registered range
> +generates a notification
> +once the range has been protected with
> +.BR UFFDIO_RWPROTECT (2const).
> +This mode cannot be combined with
> +.BR UFFDIO_REGISTER_MODE_WP ;
> +attempting to do so fails with
> +.BR EINVAL .
> +Anonymous, shmem, and hugetlbfs ranges are compatible.
>  .P
>  If the operation is successful, the kernel modifies the
>  .I argp->ioctls
> @@ -109,6 +123,16 @@ .SH DESCRIPTION
>  The
>  .B UFFDIO_POISON
>  operation is supported.
> +.TP
> +.BR "1 << _UFFDIO_RWPROTECT" " (since Linux 7.2)"
> +The
> +.B UFFDIO_RWPROTECT
> +operation is supported.
> +This bit is reported only when the range was registered with
> +.B UFFDIO_REGISTER_MODE_RWP
> +(which itself requires
> +.B UFFD_FEATURE_RWP
> +to have been negotiated).
>  .SH RETURN VALUE
>  On success,
>  0 is returned.
> -- 
> 2.54.0
> 
> 

-- 
<https://www.alejandro-colomar.es>

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