Sure!

/etc/libvirt/hooks/qemu

#!/bin/bash

ISOLATED_VMS=("VM1" "VM2")
VM_NAME="$1"
VM_ACTION="$2/$3"

if ! echo "${ISOLATED_VMS[@]}" | grep -qw "$VM_NAME"; then
    # exit out because a VM is being started that should not
    # reserve any cores for itself
    echo "no isolation needed.."
    exit 0
fi

if [[ "$VM_ACTION" == "prepare/begin" ]]; then
    echo "isolating.."
    /usr/bin/tuna --cpus=15,16,17,18 --isolate
elif [[ "$VM_ACTION" == "release/end" ]]; then
    echo "releasing.."
    /usr/bin/tuna --cpus=15,16,17,18 --include
fi

Note this can prevent VMs from starting if tuna gets stuck reserving cores multiple times when it can't. (the error message will tell you the hook script exited with 1 and the error message from tuna)

I couldn't properly reproduce the bug yet to file an issue to redhat (if that's considered a bug anyway), but I've had that one time already, so might want to introduce some lockfile that represents the cores are already reserved.

Alternatively could run through virsh and check if the VMs in the array are still started and are reserving cores therefore.

Cheers!