1.1.9 Virtualization

The following notable virtualization features are implemented in Unbreakable Enterprise Kernel Release 5 Update 1:

  • Backported bug fixes and features for KVM, Xen and Hyper-V.  Many bug fixes and virtualization features in the upstream 4.17, 4.18 and 4.19 kernels are backported into UEK R5U1. These patches offer better stability and resolve bugs and performance issues in KVM, Xen and Hyper-V. Fixes also include specific updates to better accommodate and support KVM on 64-bit Arm platforms.

  • Added the net_failover driver module.  The addition of the net_failover driver module in this update release helps to enable virtio_net to act as a standby for a passthru device. This is important in cloud environments where implementing an accelerated data path to virtio-net enabled virtual machines should be possible with minimal guest user space modification. In particular, the net_failover module provides an automated failover mechanism for paravirtual drivers to manage network devices in a generic failover infrastructure.

  • KVM Guest startup issue fixed for system where Transparent Huge Pages (THP) are enabled.  An issue that caused a large-memory KVM guest to hang on startup or restart when using Transparent Huge Pages (THP), has been resolved in this update. The issue resulted from a memory mapping heuristic that broke when a local node ran out of memory.

    To prevent this issue from occurring, where a kernel does not have a fix applied, run the following command on the host system before you attempt to start the guest:

    # echo defer > /sys/kernel/mm/transparent_hugepage/defrag

    A fix for this issue is included in this update release and systems using this kernel version, or later, do not require the workaround.