Several patches for the Xen Hypervisor that were backported from changes in the Linux 4.11 and 4.12 kernel releases are included in this update. Many of these patches improve performance, error handling, and also provide general bug fixes.

The following are the notable fixes and improvements that have been made in this update:

• A patch was applied to the Xen memory management code to resolve an issue where overlapping memory allocation could have resulted in a kernel panic on a guest virtual machine.

• A patch was applied to prevent the printing of the following unnecessary error message, which appears in the dmesg output when booting a PV guest:

  Unable to read sysrq code in control/sysrq

• Patches have been applied in this update to improve security for Xen.

• This update includes improved support for NVMe devices by Xen guests.

• Patches were applied and updated in the Xen blkfront module to optimize the management of grants in the blkfront ring by ensuring that persistent grants are always allocated first. This change is also implemented to avoid an I/O hang when there are very few, but enough, grants available.

• A patch has been applied to fix a race condition that could result in an I/O hang in the blkfront driver.

• Logging improvements that help with debugging grant management in Xen block drivers have been included in this update.