> From: Paraschiv, Andra-Irina <andraprs@xxxxxxxxxx> > Sent: Friday, April 24, 2020 9:59 PM > > > On 24/04/2020 12:59, Tian, Kevin wrote: > > > >> From: Paraschiv, Andra-Irina > >> Sent: Thursday, April 23, 2020 9:20 PM > >> > >> 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. > >> > >> 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. > > sounds like a firecracker VM? > > It's a VM crafted for enclave needs. > > > > >> 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. > > In last paragraph, you said that the enclave VM uses its own memory and > > CPUs. Then here, you said the memory/CPUs are carved out and dedicated > > from the primary VM. Can you elaborate which one is accurate? or a mixed > > model? > > Memory and CPUs are carved out of the primary VM and are dedicated for > the enclave VM. I mentioned above as "its own" in the sense that the > primary VM doesn't use these carved out resources while the enclave is > running, as they are dedicated to the enclave. > > Hope that now it's more clear. yes, it's clearer. > > > > >> > >> 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. > > How does the application in the primary VM assign task to be executed > > in the enclave VM? I didn't see such command in this series, so suppose > > it is also communicated through virtio-vsock? > > The application that runs in the enclave needs to be packaged in an > enclave image together with the OS ( e.g. kernel, ramdisk, init ) that > will run in the enclave VM. > > Then the enclave image is loaded in memory. After booting is finished, > the application starts. Now, depending on the app implementation and use > case, one example can be that the app in the enclave waits for data to > be fetched in via the vsock channel. > OK, I thought the code/data was dynamically injected from the primary VM and then run in the enclave. From your description it sounds like a servicing model that an auto-running application wait for and respond service request from the application in the primary VM. Thanks Kevin
