virt-mem support

[mkutouski]

Description Add support for virt-mem. It has certain advantages over ballooning and hotplug dimm. Quoted from the project's home page:

The main goal of virtio-mem is to allow for dynamic resizing of virtual machine memory. virtio-mem provides a flexible, cross-architecture memory hot(un)plug solution that avoids many limitations imposed by existing technologies, architectures, and interfaces: paravirtualized memory hot(un)plug.

More links to check: 1, 2.

Use case Use cases are the same as for dynamical resizing of VM memory but it seems virt-mem has advantages over currently supported by OpenNebula modes (ballooning and hotplug). Quoted from here:

• Unified memory hot(un)plug for all architectures
  • avoid mixing technologies (e.g. ACPI and virtio)
• Manage size changes completely inside QEMU
  • Don’t require e.g. plugged DIMMs on command line
  • Simplify migration
• Provide a safe way to detect malicious guests
  • Unplugged memory should not be reused by mistake
• Support different page sizes/huge pages
• Support NUMA

Interface Changes One needs to add one more item (virt-mem?) in the drop-down menu for "Memory Resize Mode" field in "General" tab of VM template menu.

Progress Status

• [ ] Code committed
• [ ] Testing - QA
• [ ] Documentation (Release notes - resolved issues, compatibility, known issues)