Microsoft Hyper-V Balloon driver

modulename: hv_balloon.ko

configname: CONFIG_HYPERV_BALLOON

Linux Kernel Configuration
└─>Device Drivers
└─>Microsoft Hyper-V guest support
└─>Microsoft Hyper-V Balloon driver
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Select this option to enable Hyper-V Balloon driver.

source code: