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

Paraschiv, Andra-Irina
2020-04-24T09:54:47Z

On 24/04/2020 11:19, Paraschiv, Andra-Irina wrote:
>
>
> 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.

And just to be a bit more clear, the reply above takes into
consideration that it's not emulated in QEMU.

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
>>>
>>>
>>>
>>>
>>> Amazon Development Center (Romania) S.R.L. registered office: 27A
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