Re: [PATCH v1 00/15] Add support for Nitro Enclaves

Paolo Bonzini
2020-04-23T13:42:49Z

On 23/04/20 15:19, Paraschiv, Andra-Irina wrote:
> 2. The enclave itself - a VM running on the same host as the primary VM
> that spawned it.
>
> The enclave VM has no persistent storage or network interface attached,
> it uses its own memory and CPUs + its virtio-vsock emulated device for
> communication with the primary VM.
>
> The memory and CPUs are carved out of the primary VM, they are dedicated
> for the enclave. The Nitro hypervisor running on the host ensures memory
> and CPU isolation between the primary VM and the enclave VM.
>
> These two components need to reflect the same state e.g. when the
> enclave abstraction process (1) is terminated, the enclave VM (2) is
> terminated as well.
>
> With regard to the communication channel, the primary VM has its own
> emulated virtio-vsock PCI device. The enclave VM has its own emulated
> virtio-vsock device as well. This channel is used, for example, to fetch
> data in the enclave and then process it. An application that sets up the
> vsock socket and connects or listens, depending on the use case, is then
> developed to use this channel; this happens on both ends - primary VM
> and enclave VM.
>
> Let me know if further clarifications are needed.

Thanks, this is all useful. However can you please clarify the
low-level details here?

>> - the initial CPU state: CPL0 vs. CPL3, initial program counter, etc.
>> - the communication channel; does the enclave see the usual local APIC
>> and IOAPIC interfaces in order to get interrupts from virtio-vsock, and
>> where is the virtio-vsock device (virtio-mmio I suppose) placed in
>> memory?
>> - what the enclave is allowed to do: can it change privilege levels,
>> what happens if the enclave performs an access to nonexistent memory,
>> etc.
>> - whether there are special hypercall interfaces for the enclave

Thanks,

Paolo