linux-kernel - Re: [PATCH RFC v2 02/29] x86: Create CONFIG_MITIGATION_ADDRESS_SPACE

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Message-ID: <20250116164305.GEZ4k3Gd2IoJpJzEIl@fat_crate.local>
Date: Thu, 16 Jan 2025 17:43:05 +0100
From: Borislav Petkov <bp@...en8.de>
To: Brendan Jackman <jackmanb@...gle.com>
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Subject: Re: [PATCH RFC v2 02/29] x86: Create
 CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION

On Fri, Jan 10, 2025 at 06:40:28PM +0000, Brendan Jackman wrote:
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 7b9a7e8f39acc8e9aeb7d4213e87d71047865f5c..5a50582eb210e9d1309856a737d32b76fa1bfc85 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2519,6 +2519,20 @@ config MITIGATION_PAGE_TABLE_ISOLATION
>  
>  	  See Documentation/arch/x86/pti.rst for more details.
>  
> +config MITIGATION_ADDRESS_SPACE_ISOLATION
> +	bool "Allow code to run with a reduced kernel address space"
> +	default n
> +	depends on X86_64 && !PARAVIRT && !UML
> +	help
> +	  This feature provides the ability to run some kernel code

s/This feature provide/Provide/

> +	  with a reduced kernel address space. This can be used to
> +	  mitigate some speculative execution attacks.
> +
> +	  The !PARAVIRT dependency is only because of lack of testing; in theory
> +	  the code is written to work under paravirtualization. In practice
> +	  there are likely to be unhandled cases, in particular concerning TLB
> +	  flushes.

Right, this paragraph should be under the "---" line too until PARAVIRT gets
tested, ofc.

Thx.

-- 
Regards/Gruss,
    Boris.

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