How to build qemu using upstream 4.x version ?

[Kvasscn]

I found a description about how to buid a custom qemu at the link https://github.com/kata-containers/documentation/blob/master/Developer-Guide.md#build-a-custom-qemu,
but it use the qemu-lite branch, not the latest qemu version.

At the kata 1.8.0 release note, it already upgrades the qemu from qemu-lite to upstream qemu 4.0,
but the developer-guide document has not mentioned how to build it.

[amshinde]

@GabyCT @jcvenegas Want to take a look at this?

[Kvasscn]

I tried the following methed refer to the link https://www.qemu.org/download/#source
Firstly, to get the qemu source code:
$ wget https://download.qemu.org/qemu-4.1.0.tar.xz
$ tar xvJf qemu-4.1.0.tar.xz

or download source code from git:
$ git clone https://git.qemu.org/git/qemu.git
$ cd qemu
$ git submodule init
$ git submodule update --recursive

Secondly, to build qemu using configure-hypervisor.sh script and make command:
$ go get -d github.com/kata-containers/packaging
$ cd $your_qemu_directory
$ ${GOPATH}/src/github.com/kata-containers/packaging/scripts/configure-hypervisor.sh qemu > kata.cfg
$ eval ./configure "$(cat kata.cfg)"
$ make -j $(nproc)
$ sudo -E make install

The qemu binary file can work with kata, but not support virtio-fs feature.

[jcvenegas]

@Kvasscn something like that is good, I also think about reference to
https://github.com/kata-containers/tests/blob/master/.ci/install_qemu.sh#L80 in the docs. because is a script under .ci I am not sure how good is to refernce as it could change at any moment.

About virtiofs qemu vanilla support we are working on that we need to add it event to the CI.