3.3. Known Issues

The BOOTIF=link argument is currently not supported for Red Hat Enterprise Linux 7.0 Hypervisors.

This release does not support registering Red Hat Enterprise Virtualization Hypervisors to RHN with a proxy.

If the SPICE ActiveX plug-in fails, make sure you have installed the Microsoft update at https://technet.microsoft.com/library/security/MS15-065. See https://support.microsoft.com/en-us/kb/3072449 for more information.

Red Hat Enterprise Linux 7 virtualization hosts now support Virtual Function I/O (VFIO), a new UIO-like kernel driver that allows for a cleaner PCI device assignment architecture in KVM.

Note that IOMMU support needs to be enabled manually on the host's kernel command line. For GPU passthrough, additional kernel configuration is needed: for example, in the case of nvidia, the default driver needs to be avoided in both the host and the guest (via blacklisting of the OSS driver, and by binding the PCI device to the pci-stub driver on the host).

On some Red Hat Enterprise Virtualization Hypervisor hosts, a device-mapper error (device-mapper: table: 253:6: multipath: error getting device) is displayed on the login screen. This error does not have a functional impact on those hosts.

Due to the QEMU known issue (see BZ#1262143), ppc64le virtual machines takes longer to start. To work around this issue, the default virtual machine maximum memory setting for ppc64le systems is set to 1TB instead of 4TB on x86_64 systems. This default can be increased, however then it takes a few minutes for a ppc64le virtual machine to start.

The startup time for virtual machines with large memory is slow on IBM POWER8 hosts. Therefore the default maximum memory was decreased to 1TB so the delay in the start up time was not noticeable. To change the default value, use the engine configuration tool with the VM64BitMaxMemorySizeInMB key.

Aborting the media integrity check during Red Hat Enterprise Virtualization Hypervisor 7.0 boot causes system halt and failure to boot. Remove the kernel argument rd.live.check from the kernel command line to prevent the media check on boot.

If the same iSCSI target is used to create two or more storage domains, even if the storage domain is put into maintenance mode, the iscsi session does not get logged out. Red Hat recommends to use different iSCSI targets to create different storage domains. To work around this issue, restart the hypervisor host.

V2V conversion is not supported on ppc64le-based hosts.

Large virtual machines have a significant overhead on Red Hat Enterprise Linux hosts on IBM POWER8 hardware, which is not accounted for when scheduling the virtual machine. 1/128th of the virtual machine memory size is required to be available on the host as a consecutive non-swapped block of memory. The end-user effect is that sometimes virtual machines do not run, even though the memory on the host seems to be sufficient.

Previously, changing the host name of the Manager machine when the machine also provided a local ISO storage domain was prevented by the rename tool, to prevent the ISO storage domain losing connectivity during the renaming process. Also, changing the host name of the Manager machine when the machine also provided a local data domain could cause running virtual machines to become stuck due to the hosts losing connectivity with their virtual disks. Now, the rename tool checks both of these, and guides the user to eject/shut down/put to maintenance any required virtual machines or storage domains, and only then allows the rename process to continue. To change the host name of the Manager machine, see the product documentation: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Virtualization/3.6/html-single/Administration_Guide/index.html#sect-The_oVirt_Engine_Rename_Tool

Red Hat Enterprise Linux 7.2 virtual machines running on PPC64 hosts will crash during hot plug/unplug if the kernel version on the virtual machine is older than kernel-3.10.0-327.2.1.el7, or if the host kernel is older than this version.

The Disk Alignment feature is unavailable for PPC.