Re: [PATCH v2 00/24] Opt-in always-on nVHE hypervisor

Marc Zyngier
2020-11-23T13:45:13Z

On Mon, 16 Nov 2020 20:42:54 +0000,
David Brazdil <dbrazdil@google.com> 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.