QEMU emulator detection

[vholer]

Description

Currently, the default path to the QEMU is hardcoded in the vmm_exec_kvm.conf :

https://github.com/OpenNebula/one/blob/6230e2d7c6ff5f037bad17684fda94beb116f3ed/src/vmm_mad/exec/vmm_exec_kvm.conf#L31

and, adjusted for each build platform during the packaging to

• CentOS / RHEL: /usr/libexec/qemu-kvm
• Fedora: /usr/bin/qemu-kvm
• Debian / Ubuntu: /usr/bin/qemu-system-x86_64

This introduces following problems in

• heterogenous environments (e.g., F-E CentOS, HV mixed Debian and CentOS) - and requires to a symlink incompatible systems to provide emulator on a same path within all platforms

• different architectures, where that (e.g., OS=[arch="aarch64"]) requires a completely different emulator (e.g., /usr/bin/qemu-system-aarch64).

Vague proposal is to:

1. extend probes fetching current KVM_CPU* and KVM_MACHINES to return

   • list supported architectures
   • emulator for each architecture
   • KVM_CPU/MACHINES specific for each architecture

2. Use a VM defaults specific for planned host.

Use case

• Simplify configuration for heterogenous environments.
• Front-end container deployment is is fixed to a single platform no matter what's running on HVs
• Improve support for non-x86 architectures.

Interface Changes Monitoring, oned, Sunstone.

Progress Status

• [ ] Branch created
• [ ] Code committed to development branch
• [ ] Testing - QA
• [ ] Documentation
• [ ] Release notes - resolved issues, compatibility, known issues
• [ ] Code committed to upstream release/hotfix branches
• [ ] Documentation committed to upstream release/hotfix branches

[vholer]

PRs to merge into master as a workaround which uses unified /usr/bin/qemu-kvm-one symlink:

• https://github.com/OpenNebula/one-ee/pull/529/
• https://github.com/OpenNebula/packages/pull/193
• https://github.com/OpenNebula/docs/pull/1379

The issue should be left opened for a proper solution, which inteligently takes emulator and respects the guest VM architecture,