When a user request for a virtual machine in the cloud, the cloud provider needs to allocate a VM for the user.
There are three concerns a cloud provider needs to take into account when doing the VM allocation.
- Load Balance
- Power Consumption
- For security, we aim to avoid the cloud covert channel attacks in which an attacker seeks to be co-locate with the target VM in order to extract private information from the victims.
Popular VM Allocation Policies
The following table  shows the popular VM allocation policies.
 Using Virtual Machine Allocation Policies to Defend against Co-resident Attacks in Cloud Computing, by Yi Han et al, in Transactions on Dependable and Secure Computing