Adding dedicated runners to Gitlab CI

[Stefan Hajnoczi]

Hi Cleber,
I noticed there are already two dedicated runners registered in QEMU's
Gitlab CI and you have documented gitlab-runner setup steps in a patch
series on the mailing list.

A few higher-level questions come to mind. Maybe you could document
this when you send the next version of the CI patches:

What about the process for adding a new dedicated runner?

Who should I talk to get a machine added?

What are the security implications?

Who is responsible if a runner starts failing certain tests?

What happens if the runner disconnects from Gitlab CI?

Thanks,
Stefan