Re: [PATCHv3 17/17] x86: Introduce CONFIG_X86_INTEL_MKTME

Dave Hansen
2018-06-13T18:46:39Z

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
>