Date:   Wed, 19 Aug 2020 13:15:59 +0200
From:   Alexander Graf <graf@...zon.de>
To:     Andra Paraschiv <andraprs@...zon.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     Anthony Liguori <aliguori@...zon.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Colm MacCarthaigh <colmmacc@...zon.com>,
        "David Duncan" <davdunc@...zon.com>,
        Bjoern Doebel <doebel@...zon.de>,
        "David Woodhouse" <dwmw@...zon.co.uk>,
        Frank van der Linden <fllinden@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Karen Noel <knoel@...hat.com>,
        "Martin Pohlack" <mpohlack@...zon.de>,
        Matt Wilson <msw@...zon.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Balbir Singh <sblbir@...zon.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stewart Smith <trawets@...zon.com>,
        Uwe Dannowski <uwed@...zon.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        kvm <kvm@...r.kernel.org>,
        ne-devel-upstream <ne-devel-upstream@...zon.com>
Subject: Re: [PATCH v7 00/18] Add support for Nitro Enclaves



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?

Reviewed-by: Alexander Graf <graf@...zon.com>


Alex



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