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

Paraschiv, Andra-Irina
2020-04-24T08:20:01Z

On 24/04/2020 06:04, Longpeng (Mike, Cloud Infrastructure Service
Product Dept.) wrote:
> On 2020/4/23 21:19, Paraschiv, Andra-Irina wrote:
>>
>> On 22/04/2020 00:46, Paolo Bonzini wrote:
>>> On 21/04/20 20:41, Andra Paraschiv wrote:
>>>> An enclave communicates with the primary VM via a local communication channel,
>>>> using virtio-vsock [2]. An enclave does not have a disk or a network device
>>>> attached.
>>> Is it possible to have a sample of this in the samples/ directory?
>> I can add in v2 a sample file including the basic flow of how to use the ioctl
>> interface to create / terminate an enclave.
>>
>> Then we can update / build on top it based on the ongoing discussions on the
>> patch series and the received feedback.
>>
>>> I am interested especially in:
>>>
>>> - 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
>> An enclave is a VM, running on the same host as the primary VM, that launched
>> the enclave. They are siblings.
>>
>> Here we need to think of two components:
>>
>> 1. An enclave abstraction process - a process running in the primary VM guest,
>> that uses the provided ioctl interface of the Nitro Enclaves kernel driver to
>> spawn an enclave VM (that's 2 below).
>>
>> How does all gets to an enclave VM running on the host?
>>
>> There is a Nitro Enclaves emulated PCI device exposed to the primary VM. The
>> driver for this new PCI device is included in the current patch series.
>>
> Hi Paraschiv,
>
> The new PCI device is emulated in QEMU ? If so, is there any plan to send the
> QEMU code ?

Hi,

Nope, not that I know of so far.

Thanks,
Andra

>
>> The ioctl logic is mapped to PCI device commands e.g. the NE_ENCLAVE_START ioctl
>> maps to an enclave start PCI command or the KVM_SET_USER_MEMORY_REGION maps to
>> an add memory PCI command. The PCI device commands are then translated into
>> actions taken on the hypervisor side; that's the Nitro hypervisor running on the
>> host where the primary VM is running.
>>
>> 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.
>>
>>>> The proposed solution is following the KVM model and uses the KVM API to be able
>>>> to create and set resources for enclaves. An additional ioctl command, besides
>>>> the ones provided by KVM, is used to start an enclave and setup the addressing
>>>> for the communication channel and an enclave unique id.
>>> Reusing some KVM ioctls is definitely a good idea, but I wouldn't really
>>> say it's the KVM API since the VCPU file descriptor is basically non
>>> functional (without KVM_RUN and mmap it's not really the KVM API).
>> It uses part of the KVM API or a set of KVM ioctls to model the way a VM is
>> created / terminated. That's true, KVM_RUN and mmap-ing the vcpu fd are not
>> included.
>>
>> Thanks for the feedback regarding the reuse of KVM ioctls.
>>
>> Andra
>>
>>
>>
>>
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