[edk2-devel] [RFC] Design review for Lazy Page Accept in TDVF

[Gerd Hoffmann]

On Mon, Aug 30, 2021 at 07:49:27AM +0000, Gao, Jiaqi wrote:
> Motivation: Intel TDX provides memory encryption and integrity
> multi-tenancy for hardware protection. A TD-guest uses TDCALL to
> accept shared memory as private. However, accept whole system memory
> may take a long time which will have an adverse impact on the boot
> time performance.

Which order of magnitude do we talk about?
How long would it take to accept 2G of memory (all memory below 4g on
qemu q35) ?

> We propose three options to address this issue:

>   1.  Modifying the memory allocation (MdeModulePkg/Core/Dxe/Mem) logic to accept memory when OUT_OF_RESOURCE occurs.
>   2.  Changing the process flow of QEMU direct boot and GRUB to accept memory when loading the image fails and returns OUT_OF_RESOURCE.
>   3.  Adding AcceptMemory() as a boot service interface to simplify the implementation of option 2.
> Underlying implementation of accepting memory is provided by a protocol which can be installed by architecture-specific drivers such as TdxDxe.

(1) Looks best to me.  From a design point of view it is a very
reasonable thing for the core memory manager to also manage the
accepted/unaccepted state of memory.  It avoids duplicating the
"oom -> try AcceptMemoryRessource()" logic in bootloaders and
will also cover other oom situations.

take care,
  Gerd



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