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Message-ID: <808ed933-fbc6-4ace-812c-08170b51d699@amperemail.onmicrosoft.com>
Date: Tue, 10 Dec 2024 17:47:05 +0800
From: Shijie Huang <shijie@...eremail.onmicrosoft.com>
To: Anshuman Khandual <anshuman.khandual@....com>,
 Ard Biesheuvel <ardb@...nel.org>
Cc: Huang Shijie <shijie@...amperecomputing.com>, catalin.marinas@....com,
 will@...nel.org, corbet@....net, patches@...erecomputing.com, cl@...ux.com,
 akpm@...ux-foundation.org, thuth@...hat.com, rostedt@...dmis.org,
 xiongwei.song@...driver.com, inux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] arm64: refactor the rodata=xxx


On 2024/12/10 16:38, Anshuman Khandual wrote:
>
> On 12/10/24 12:51, Ard Biesheuvel wrote:
>> On Tue, 10 Dec 2024 at 08:17, Anshuman Khandual
>> <anshuman.khandual@....com> wrote:
>> ...
>>> Reformatted and cleaned up the above comment a bit but feel free to
>>> improve it further.
>>>
>>> /*
>>>   * rodata=on (default)
>>>   *
>>>   *    This applies read-only attributes to VM areas and to the linear
>>>   *    alias of the backing pages as well. This prevents code or read-
>>>   *    only data from being modified (inadvertently or intentionally),
>>>   *    via another mapping for the same memory page.
>>>   *
>>>   *    But this might cause linear map region to be mapped down to base
>>>   *    pages, which may adversely affect performance in some cases.
>>>   *
>>>   * rodata=off
>>>   *
>>>   *    This provides more block mappings and contiguous hints for linear
>>>   *    map region which would minimize TLB footprint. This also leaves
>>>   *    read-only kernel memory writable for debugging.
>>>   *
>>>   * rodata=noalias
>>>   *
>>>   *    This provides more block mappings and contiguous hints for linear
>>>   *    map region which would minimize TLB footprint. Linear aliases of
>>>   *    pages belonging to read-only mappings in vmalloc region are also
>>>   *    marked as read-only.
>>>
>> If linear aliases are marked as read-only, how does 'noalias' differ from 'on'?
> Right, the last sentence can be can dropped.

Okay, no problem.


Thanks

Huang Shijie


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