Re: [PATCH v9 7/7] coco: guest: arm64: Replace dummy CCA device with sysfs ABI

[Jason Gunthorpe]

> [ ... 10 lines skipped ... ]
> Add /sys/firmware/cca/realm_guest as a stable, architecture-provided ABI
> for detecting whether the kernel is running as an Arm CCA Realm guest. The
> file returns 1 in Realm world and 0 otherwise, similar to the existing s390
> /sys/firmware/uv/prot_virt_guest interface for protected virtualization
> guests.

Is this the case? the uv code is blocked by:

	if (!test_facility(158))
		return 0;

Which AI is telling me means the FW supports "ultravisor", so I think
that would be broadly equivilent on ARM to FW supporting RMM.

ie don't create a firmware/cca unconditionally, look for some sign
that RMM is present first?

The rest makes sense to me.

-- 
Jason