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33 lines
1.8 KiB
33 lines
1.8 KiB
# vHost
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A pure rust library for vDPA, vhost and vhost-user.
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The `vhost` crate aims to help implementing dataplane for virtio backend drivers. It supports three different types of dataplane drivers:
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- vhost: the dataplane is implemented by linux kernel
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- vhost-user: the dataplane is implemented by dedicated vhost-user servers
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- vDPA(vhost DataPath Accelerator): the dataplane is implemented by hardwares
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The main relationship among Traits and Structs exported by the `vhost` crate is as below:
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## Kernel-based vHost Backend Drivers
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The vhost drivers in Linux provide in-kernel virtio device emulation. Normally
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the hypervisor userspace process emulates I/O accesses from the guest.
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Vhost puts virtio emulation code into the kernel, taking hypervisor userspace
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out of the picture. This allows device emulation code to directly call into
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kernel subsystems instead of performing system calls from userspace.
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The hypervisor relies on ioctl based interfaces to control those in-kernel
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vhost drivers, such as vhost-net, vhost-scsi and vhost-vsock etc.
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## vHost-user Backend Drivers
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The [vhost-user protocol](https://qemu.readthedocs.io/en/latest/interop/vhost-user.html#communication) aims to implement vhost backend drivers in
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userspace, which complements the ioctl interface used to control the vhost
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implementation in the Linux kernel. It implements the control plane needed
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to establish virtqueue sharing with a user space process on the same host.
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It uses communication over a Unix domain socket to share file descriptors in
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the ancillary data of the message.
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The protocol defines two sides of the communication, master and slave.
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Master is the application that shares its virtqueues, slave is the consumer
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of the virtqueues. Master and slave can be either a client (i.e. connecting)
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or server (listening) in the socket communication.
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