- When a KVM virtual machine (VM) running on a Red Hat Enterprise Linux 6 host was suspended to disk and then restored, the system time on the VM in some cases did not correctly synchronize with the system time on the host. With this update, the kvm-clock utility has been modified to reliably read the system time on the host, and the described problem no longer happens.
- Support has been added for qemu-kvm trace events during the system shutdown process, which allows users to get detailed diagnostics about systems shutdown requests issued by the "virsh shutdown" command or the virt-manager application. This provides users with enhanced capabilities for debugging KVM guest problems during shutdown.
- The qemu-img tool now uses the fallocate() system call when the "preallocation=full" option is specified. This makes the preallocation operation significantly faster if "preallocation=full" is used, and thus shortens the time necessary to prepare a new guest.
- With this update, qemu-kvm supports the "cache=directsync" option in the host file, which enables the use of the directsync cache mode on virtual disks. When "cache=directsync" is used, write operations on the guest are only completed when data is safely present on the disk, which increases data security during file transactions between guests.