On Mon, 16 Nov 2020 20:42:54 +0000,
David Brazdil [off-list ref] wrote:

As we progress towards being able to keep guest state private to the
host running nVHE hypervisor, this series allows the hypervisor to
install itself on newly booted CPUs before the host is allowed to run
on them.

All functionality described below is opt-in, guarded by an early param
'kvm-arm.protected'. Future patches specific to the new "protected" mode
should be hidden behind the same param.

The hypervisor starts trapping host SMCs and intercepting host's PSCI
CPU_ON/SUSPEND calls. It replaces the host's entry point with its own,
initializes the EL2 state of the new CPU and installs the nVHE hyp vector
before ERETing to the host's entry point.

The kernel checks new cores' features against the finalized system
capabilities. To avoid the need to move this code/data to EL2, the
implementation only allows to boot cores that were online at the time of
KVM initialization and therefore had been checked already.

Other PSCI SMCs are forwarded to EL3, though only the known set of SMCs
implemented in the kernel is allowed. Non-PSCI SMCs are also forwarded
to EL3. Future changes will need to ensure the safety of all SMCs wrt.
private guests.

The host is still allowed to reset EL2 back to the stub vector, eg. for
hibernation or kexec, but will not disable nVHE when there are no VMs.

Tested on Rock Pi 4b, based on 5.10-rc4.

Adding Lorenzo and Sudeep for the PSCI side of things.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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