The warning you're encountering on your Oracle Ubuntu 22.04 ARM instance indicates that KVM (Kernel-based Virtual Machine) is not available. This can happen for several reasons, such as:

1. KVM is not installed on the system.
2. KVM kernel modules are not loaded.
3. Virtualization extensions are not enabled in the BIOS/UEFI (though this is less likely on cloud instances).
4. The system does not support nested virtualization (common in cloud environments).

Since you're using an Oracle Cloud ARM instance, nested virtualization is often disabled by default for security and performance reasons. However, you can still check and attempt to enable KVM if your instance supports it.

Steps to Diagnose and Fix the Issue

1. Check if KVM is Supported on Your Instance

Run the following command to check if your CPU supports virtualization:

egrep -c '(vmx|svm)' /proc/cpuinfo

• If the output is 0, your CPU does not support hardware virtualization (common on ARM instances unless explicitly enabled).
• If the output is 1 or higher, your CPU supports virtualization, but KVM may still be disabled.

For ARM-based systems, check for KVM support with:

ls /dev/kvm

• If /dev/kvm exists, KVM is available.
• If it does not exist, KVM is not available.

2. Install KVM (if not installed)

If KVM is supported but not installed, run:

sudo apt update
sudo apt install -y qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils

3. Load KVM Kernel Modules

If KVM is installed but the modules are not loaded, run:

sudo modprobe kvm
sudo modprobe kvm_arm  # For ARM-based systems

Check if the modules are loaded:

lsmod | grep kvm

If you see kvm and kvm_arm in the output, the modules are loaded.

4. Check if Nested Virtualization is Enabled

On Oracle Cloud ARM instances, nested virtualization is often disabled by default. You can check if it's enabled with:

cat /sys/module/kvm_arm/parameters/nested

• If the output is Y or 1, nested virtualization is enabled.
• If the output is N or 0, it is disabled.

Enabling Nested Virtualization (if supported)

Nested virtualization is not always supported on ARM instances in the cloud. If your instance supports it, you can try enabling it with:

echo "options kvm_arm nested=1" | sudo tee /etc/modprobe.d/kvm_arm.conf
sudo modprobe -r kvm_arm
sudo modprobe kvm_arm

Then verify:

cat /sys/module/kvm_arm/parameters/nested

5. Restart Required Services

After making changes, restart the libvirtd service:

sudo systemctl restart libvirtd

6. Verify KVM Availability

Run:

kvm-ok

• If the output says KVM acceleration can be used, KVM is working.
• If not, KVM is still not available.

7. Fallback: Use QEMU with TCG (if KVM is unavailable)

If KVM is not available (e.g., nested virtualization is disabled on your cloud instance), you can still run VMs using QEMU with TCG (Tiny Code Generator), but performance will be significantly slower.

To use QEMU without KVM:

qemu-system-aarch64 -enable-kvm  # This will fail if KVM is unavailable
qemu-system-aarch64              # Falls back to TCG (slow)

Oracle Cloud-Specific Notes

• Oracle Cloud ARM instances (e.g., Ampere A1) do not support nested virtualization by default. You cannot enable KVM inside an Oracle Cloud ARM instance for running nested VMs. If you need KVM, consider using an x86_64 instance (e.g., Intel or AMD) where nested virtualization is often supported.

• If you must use ARM, you can only run VMs in emulation mode (TCG), which is very slow and not recommended for production.

Summary of Solutions

Recommendation

If you're using Oracle Cloud ARM instances, KVM is not available for nested virtualization. You have two options:

1. Use an x86_64 instance (e.g., Intel/AMD) where KVM is supported.
2. Run VMs in emulation mode (TCG) with qemu-system-aarch64 (not recommended for performance-critical workloads).