On Wed, Aug 19, 2020 at 01:15:59PM +0200, Alexander Graf wrote: > > > On 17.08.20 15:09, Andra Paraschiv wrote: > > Nitro Enclaves (NE) is a new Amazon Elastic Compute Cloud (EC2) capability > > that allows customers to carve out isolated compute environments within EC2 > > instances [1]. > > > > For example, an application that processes sensitive data and runs in a VM, > > can be separated from other applications running in the same VM. This > > application then runs in a separate VM than the primary VM, namely an enclave. > > > > An enclave runs alongside the VM that spawned it. This setup matches low latency > > applications needs. The resources that are allocated for the enclave, such as > > memory and CPUs, are carved out of the primary VM. Each enclave is mapped to a > > process running in the primary VM, that communicates with the NE driver via an > > ioctl interface. > > > > In this sense, there are two components: > > > > 1. An enclave abstraction process - a user space process running in the primary > > VM guest that uses the provided ioctl interface of the NE driver to spawn an > > enclave VM (that's 2 below). > > > > There is a NE emulated PCI device exposed to the primary VM. The driver for this > > new PCI device is included in the NE driver. > > > > The ioctl logic is mapped to PCI device commands e.g. the NE_START_ENCLAVE ioctl > > maps to an enclave start 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. The Nitro > > hypervisor is based on core KVM technology. > > > > 2. The enclave itself - a VM running on the same host as the primary VM that > > spawned it. Memory and CPUs are carved out of the primary VM and are dedicated > > for the enclave VM. An enclave does not have persistent storage attached. > > > > The memory regions carved out of the primary VM and given to an enclave need to > > be aligned 2 MiB / 1 GiB physically contiguous memory regions (or multiple of > > this size e.g. 8 MiB). The memory can be allocated e.g. by using hugetlbfs from > > user space [2][3]. The memory size for an enclave needs to be at least 64 MiB. > > The enclave memory and CPUs need to be from the same NUMA node. > > > > An enclave runs on dedicated cores. CPU 0 and its CPU siblings need to remain > > available for the primary VM. A CPU pool has to be set for NE purposes by an > > user with admin capability. See the cpu list section from the kernel > > documentation [4] for how a CPU pool format looks. > > > > An enclave communicates with the primary VM via a local communication channel, > > using virtio-vsock [5]. The primary VM has virtio-pci vsock emulated device, > > while the enclave VM has a virtio-mmio vsock emulated device. The vsock device > > uses eventfd for signaling. The enclave VM sees the usual interfaces - local > > APIC and IOAPIC - to get interrupts from virtio-vsock device. The virtio-mmio > > device is placed in memory below the typical 4 GiB. > > > > 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. The enclave VM has its own kernel and follows the standard Linux > > boot protocol. > > > > The kernel bzImage, the kernel command line, the ramdisk(s) are part of the > > Enclave Image Format (EIF); plus an EIF header including metadata such as magic > > number, eif version, image size and CRC. > > > > Hash values are computed for the entire enclave image (EIF), the kernel and > > ramdisk(s). That's used, for example, to check that the enclave image that is > > loaded in the enclave VM is the one that was intended to be run. > > > > These crypto measurements are included in a signed attestation document > > generated by the Nitro Hypervisor and further used to prove the identity of the > > enclave; KMS is an example of service that NE is integrated with and that checks > > the attestation doc. > > > > The enclave image (EIF) is loaded in the enclave memory at offset 8 MiB. The > > init process in the enclave connects to the vsock CID of the primary VM and a > > predefined port - 9000 - to send a heartbeat value - 0xb7. This mechanism is > > used to check in the primary VM that the enclave has booted. > > > > If the enclave VM crashes or gracefully exits, an interrupt event is received by > > the NE driver. This event is sent further to the user space enclave process > > running in the primary VM via a poll notification mechanism. Then the user space > > enclave process can exit. > > > > Thank you. > > > > This version reads very well, thanks a lot Andra! > > Greg, would you mind to have another look over it? Will do, it's in my to-review queue, behind lots of other patches...
