Re: [PATCH v7 00/18] Add support for Nitro Enclaves

[Greg KH]

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...