Re: [PATCH] Ability to read the MKTME status from userspace

[Dave Hansen <dave.hansen@intel.com>]

On 6/19/20 8:02 AM, Richard Hughes wrote:
>> Someone does 'cat /proc/mktme' (or whatever) and it says "1" or
>> whatever, which means yay, encryption is on.  What do they do?
> I think "is my memory encrypted" for Intel has to be a superset of:
> 
> 1. TME in CPU info
> 2. not disabled by the platform
> 3. not using unencrypted swap
> 4. not using a memory accelerator
> 5. entire DRAM area is marked with EFI_MEMORY_CPU_CRYPTO

Also realize that this can all be true at one point in time, but can
change if memory is added.

> It seems the only way to answer the questions and make it easy for the
> consumer to know the answer is to ask the kernel for each of the 5
> different questions. At the moment we can only get 1, 3, maybe 4, soon
> to be 5, but not 2.

Actually, the accelerators I had in mind would show up in the memory map
and would have EFI_MEMORY_CPU_CRYPTO properly set by the firmware.

In any case, if we do something like this, I think it fundamentally
needs to be more fine-grained than the whole system.  It probably needs
to be on a per-NUMA-node basis.  That's really the only way for us to
provide meaningful promises about encryption to end users.