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how-to-use-virtio-mem-with-kata.md

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Kata Containers with virtio-mem

Introduction

The basic idea of virtio-mem is to provide a flexible, cross-architecture memory hot plug and hot unplug solution that avoids many limitations imposed by existing technologies, architectures, and interfaces. More details can be found in https://lkml.org/lkml/2019/12/12/681.

Kata Containers with virtio-mem supports memory resize.

Requisites

Kata Containers with virtio-mem requires Linux and the QEMU that support virtio-mem. The Linux kernel and QEMU upstream version still not support virtio-mem. @davidhildenbrand is working on them. Please use following unofficial version of the Linux kernel and QEMU that support virtio-mem with Kata Containers.

The Linux kernel is at https://github.com/davidhildenbrand/linux/tree/virtio-mem-rfc-v4. The Linux kernel config that can work with Kata Containers is at https://gist.github.com/teawater/016194ee84748c768745a163d08b0fb9.

The QEMU is at https://github.com/teawater/qemu/tree/kata-virtio-mem. (The original source is at https://github.com/davidhildenbrand/qemu/tree/virtio-mem-vfio. Its base version of QEMU cannot work with Kata Containers. So merge the commit of virtio-mem to upstream QEMU.)

Set Linux and the QEMU that support virtio-mem with following line in the Kata Containers QEMU configuration configuration-qemu.toml:

[hypervisor.qemu]
path = "qemu-dir"
kernel = "vmlinux-dir"

Enable virtio-mem with following line in the Kata Containers configuration:

enable_virtio_mem = true

Run a Kata Container utilizing virtio-mem

Use following command to enable memory overcommitment of a Linux kernel. Because QEMU virtio-mem device need to allocate a lot of memory.

$ echo 1 | sudo tee /proc/sys/vm/overcommit_memory

Use following command start a Kata Container.

$ docker run --rm -it --runtime=kata --name test busybox

Use following command set the memory size of test to default_memory + 512m.

$ docker update -m 512m --memory-swap -1 test