linux-kernel - Re: [PATCHv3 17/17] x86: Introduce CONFIG_X86_INTEL

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Date:   Wed, 13 Jun 2018 11:46:34 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv3 17/17] x86: Introduce CONFIG_X86_INTEL_MKTME

On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote:
> Add new config option to enabled/disable Multi-Key Total Memory
> Encryption support.
> 
> MKTME uses MEMORY_PHYSICAL_PADDING to reserve enough space in per-KeyID
> direct mappings for memory hotplug.

Isn't it really *the* direct mapping primarily?  We make all of them
larger, but the direct mapping is impacted too.  This makes it sound
like it applies only to the MKTME mappings.

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 4fa2cf807321..d013495bb4ae 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1513,6 +1513,23 @@ config ARCH_USE_MEMREMAP_PROT
>  	def_bool y
>  	depends on AMD_MEM_ENCRYPT
>  
> +config X86_INTEL_MKTME
> +	bool "Intel Multi-Key Total Memory Encryption"
> +	select DYNAMIC_PHYSICAL_MASK
> +	select PAGE_EXTENSION
> +	depends on X86_64 && CPU_SUP_INTEL
> +	---help---
> +	  Say yes to enable support for Multi-Key Total Memory Encryption.
> +	  This requires Intel processor that has support of the feature.

"requires an Intel processor"...

> +	  Multikey Total Memory Encryption (MKTME) is a technology that allows
> +	  transparent memory encryption in upcoming Intel platforms.

"in an upcoming"

> +	  MKTME is built on top of TME. TME allows encryption of the entirety
> +	  of system memory using a single key. MKTME allows to have multiple

"allows having multiple"...

> +	  encryption domains, each having own key -- different memory pages can
> +	  be encrypted with different keys.
> +
>  # Common NUMA Features
>  config NUMA
>  	bool "Numa Memory Allocation and Scheduler Support"
> @@ -2189,7 +2206,7 @@ config RANDOMIZE_MEMORY
>  
>  config MEMORY_PHYSICAL_PADDING
>  	hex "Physical memory mapping padding" if EXPERT
> -	depends on RANDOMIZE_MEMORY
> +	depends on RANDOMIZE_MEMORY || X86_INTEL_MKTME
>  	default "0xa" if MEMORY_HOTPLUG
>  	default "0x0"
>  	range 0x1 0x40 if MEMORY_HOTPLUG
>