Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 12.22.5.236 as permitted sender) receiver=protection.outlook.com;
 client-ip=12.22.5.236; helo=mail.nvidia.com;
From:   Alistair Popple <apopple@nvidia.com>
To:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        Peter Xu <peterx@redhat.com>
CC:     Axel Rasmussen <axelrasmussen@google.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Hugh Dickins <hughd@google.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Jerome Glisse <jglisse@redhat.com>,
        "Matthew Wilcox" <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>, <peterx@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH v6 04/23] mm/uffd: PTE_MARKER_UFFD_WP
Date:   Thu, 16 Dec 2021 16:18:50 +1100
Message-ID: <1966495.R0KUr5dvoW@nvdebian>
In-Reply-To: <20211115075522.73795-5-peterx@redhat.com>
References: <20211115075522.73795-1-peterx@redhat.com> <20211115075522.73795-5-peterx@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Dec 2021 05:18:57.2039
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 6ae5e387-0f73-4755-0ce9-08d9c0538f9b
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.236];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT052.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR1201MB0059
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Monday, 15 November 2021 6:55:03 PM AEDT Peter Xu wrote:

[...]

> +/*
> + * Returns true if this is a swap pte and was uffd-wp wr-protected in either
> + * forms (pte marker or a normal swap pte), false otherwise.
> + */
> +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_swp_uffd_wp(pte))
> +		return true;

If I'm not mistaken normal swap uffd-wp ptes can still exist when
CONFIG_PTE_MARKER_UFFD_WP=n so shouldn't this be outside the #ifdef protection?

In fact we could drop the #ifdef entirely here as it is safe to call
is_pte_marker_uffd_wp() without CONFIG_PTE_MARKER_UFFD_WP.

> +
> +	if (is_pte_marker_uffd_wp(pte))
> +		return true;
> +#endif
> +	return false;
> +}
> +
>  #endif /* _LINUX_USERFAULTFD_K_H */
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 66f23c6c2032..f01c8e0afadf 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -904,6 +904,15 @@ config PTE_MARKER
>  	help
>  	  Allows to create marker PTEs for file-backed memory.
>  
> +config PTE_MARKER_UFFD_WP
> +	bool "Marker PTEs support for userfaultfd write protection"
> +	depends on PTE_MARKER && HAVE_ARCH_USERFAULTFD_WP
> +
> +	help
> +	  Allows to create marker PTEs for userfaultfd write protection
> +	  purposes.  It is required to enable userfaultfd write protection on
> +	  file-backed memory types like shmem and hugetlbfs.
> +
>  source "mm/damon/Kconfig"
>  
>  endmenu
>