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

["Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" <longpeng2@huawei.com>]

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 ?

> 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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Regards,
Longpeng(Mike)