RE: [RFC PATCH v1 00/18] x86: Secure Memory Encryption (AMD)

[Elliott, Robert (Persistent Memory)]

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Tom Lendacky
> Sent: Tuesday, April 26, 2016 5:56 PM
> Subject: [RFC PATCH v1 00/18] x86: Secure Memory Encryption (AMD)
> 
> This RFC patch series provides support for AMD's new Secure Memory
> Encryption (SME) feature.
> 
> SME can be used to mark individual pages of memory as encrypted through the
> page tables. A page of memory that is marked encrypted will be automatically
> decrypted when read from DRAM and will be automatically encrypted when
> written to DRAM. Details on SME can found in the links below.
> 
...
> ...  Certain data must be accounted for
> as having been placed in memory before SME was enabled (EFI, initrd, etc.)
> and accessed accordingly.
> 
...
>       x86/efi: Access EFI related tables in the clear
>       x86: Access device tree in the clear
>       x86: Do not specify encrypted memory for VGA mapping

If the SME encryption key "is created randomly each time a system is booted,"
data on NVDIMMs won't decrypt properly on the next boot.  You need to exclude
persistent memory regions (reported in the UEFI memory map as 
EfiReservedMemoryType with the NV attribute, or as EfiPersistentMemory).

Perhaps the SEV feature will allow key export/import that could work for
NVDIMMs.

---
Robert Elliott, HPE Persistent Memory