ISSUE TYPE

• Bug Report

COMPONENT NAME

KVM Hypervisor Plugin - LibvirtConnection

CLOUDSTACK VERSION

Main branch (4.22+)

CONFIGURATION

KVM hypervisor type configured with LXC support. VM deployment using KVM or LXC hypervisor.

OS / ENVIRONMENT

Linux hypervisor with libvirt installed

SUMMARY

LibvirtConnection.getConnectionByVmName() does not accept or use the VM's hypervisor type, causing it to always try KVM first, then LXC. When a VM doesn't exist, it returns a potentially wrong default connection instead of throwing a meaningful error, resulting in confusing "Domain not found" messages.

STEPS TO REPRODUCE

1. Create a KVM VM (e.g., instance i-6-526-VM)
2. Fail VM creation (VM never gets to libvirt) or remove it from the host via virsh (? actually my vm was failed to create)
3. Management server continues to send CheckVirtualMachineCommand, StopCommand, etc. for the non-existent VM
4. Agent's LibvirtConnection.getConnectionByVmName("i-6-526-VM") is called
5. Method tries:
   • KVM connection → domainLookupByName returns null (VM doesn't exist)
   • LXC connection → domainLookupByName returns null (VM doesn't exist)
6. Method logs warning and returns default connection from getConnection()
7. Caller calls domainLookupByName on potentially wrong connection → "Domain not found" error

EXPECTED RESULTS

When a VM doesn't exist on the expected hypervisor, getConnectionByVmName() should throw a clear exception:

Domain not found: no domain with matching name 'i-6-526-VM' on hypervisor 'KVM'

The method should accept the hypervisor type as a parameter and use it to determine which libvirt connection to attempt.

ACTUAL RESULTS

2026-03-09 09:09:43,713 INFO  [kvm.resource.LibvirtConnection] (AgentRequest-Handler-4:[]) (logid:52f6b720) No existing libvirtd connection found. Opening a new one
2026-03-09 09:09:43,715 WARN  [kvm.resource.LibvirtConnection] (AgentRequest-Handler-4:[]) (logid:52f6b720) Can not find a connection for Instance i-6-526-VM. Assuming the default connection.
[then later] Domain not found: no domain with matching name 'i-6-526-VM'

The method silently returns a potentially incorrect connection, masking the real problem (VM was never created).

PROPOSED FIX

Add hypervisorType parameter to getConnectionByVmName():

File: plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtConnection.java

// Add new overload method
static public Connect getConnectionByVmName(String vmName, String hypervisorType) throws LibvirtException {
    // Try the specified hypervisor type first
    Connect conn = getConnectionByType(hypervisorType);
    Domain dm = conn.domainLookupByName(vmName);
    if (dm != null) {
        dm.free();
        return conn;
    }
    if (dm != null) dm.free();

    // VM not found - throw meaningful exception instead of returning wrong connection
    throw new LibvirtException("Domain not found: no domain with matching name '" + vmName + "' on hypervisor '" + hypervisorType + "'");
}

// Keep backward compatibility with existing call
static public Connect getConnectionByVmName(String vmName) throws LibvirtException {
    return getConnectionByVmName(vmName, "KVM");
}

Update callers to pass the correct hypervisor type:

• LibvirtCheckVirtualMachineCommandWrapper - use command.getContextParam(Command.HYPERVISOR_TYPE)
• LibvirtStopCommandWrapper - get VM's hypervisor type from database or command context
• Other wrappers using getConnectionByVmName()

Files to modify:

• plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtConnection.java
• plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/wrapper/LibvirtCheckVirtualMachineCommandWrapper.java
• plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/wrapper/LibvirtStopCommandWrapper.java
• All other command wrappers that call getConnectionByVmName()

ps:
maybe it's a good idea to create separate adapter for lxc but this is more for roadmap, not for bugfix.