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Date: Mon, 21 Sep 2026 15:03:32 +0200
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Subject: Re: [PATCH v2] docs/mm: describe set_memory() and set_direct_map()
 APIs
To: "Mike Rapoport (Microsoft)" <rppt@kernel.org>,
 Andrew Morton <akpm@linux-foundation.org>,
 David Hildenbrand <david@kernel.org>, Jonathan Corbet <corbet@lwn.net>
Cc: "Liam R. Howlett" <liam@infradead.org>, Lorenzo Stoakes <ljs@kernel.org>,
 Michal Hocko <mhocko@suse.com>, Randy Dunlap <rdunlap@infradead.org>,
 Shuah Khan <skhan@linuxfoundation.org>,
 Suren Baghdasaryan <surenb@google.com>, Vlastimil Babka <vbabka@kernel.org>,
 linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <20260919-set-memory-docs-v2-1-a2a4b3657690@kernel.org>
From: Kevin Brodsky <kevin.brodsky@arm.com>
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In-Reply-To: <20260919-set-memory-docs-v2-1-a2a4b3657690@kernel.org>
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On 19/09/2026 12:43, Mike Rapoport (Microsoft) wrote:
> [...]
>
> +Modifying the kernel page tables
> +================================
> +
> +Except for the vmalloc area, the kernel page tables are mostly static. Still,
> +there are cases when the permissions of existing kernel mappings have to be
> +updated, for instance when a module is loaded and its text becomes read-only
> +and executable, or when a page is temporarily removed from the direct map to
> +reduce its exposure.
> +
> +There are two families of functions for this, both declared in
> +`include/linux/set_memory.h`:
> +
> +* `set_memory_*()` change permissions of an arbitrary kernel mapping. They
> +  take a kernel virtual address and the number of pages.
> +
> +* `set_direct_map_*()` change permissions of the direct mapping of the page
> +  frame represented by a `struct page`. They take a `struct page` pointer and

The new phrasing is a mouthful but at least should be accurate :) It
should probably say "range of page frames" or something like that though.

Looks good otherwise!

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>