Red Hat ENTERPRISE LINUX 5.5 - TECHNICAL NOTES Manual page 330

Chapter 5. Known Issues
virsh define -/tmp/new-guest.xml
virsh start new-guest
• Currently, KVM cannot disable virtualization extensions on a CPU while it is being taken down.
Consequently, suspending a host running KVM-based virtual machines may cause the host to
91
(BZ#509809)
crash.
• The KSM module shipped in this release is a different version from the KSM module found on the
latest upstream kernel versions. Newer features, such as exporting statistics on the /sys filesystem,
that are implemented upstream are not in the version shipped in this release.
• The mute button in the audio control panel on a Windows virtual machine does not mute the sound.
92
BZ#482570
• Hot-unplugging of PCI devices is not supported in this release. This feature will be introduced in a
(BZ#510679)
future update.
• When migrating KVM guests between hosts, the NX CPU feature setting on both source and
destination must match. Migrating a guest between a host with the NX feature disabled (i.e. disabled
in the BIOS settings) and a host with the NX feature enabled may cause the guest to crash.
94
(BZ#516029)
• the application binary interface (ABI) between the KVM userspace (e.g. qemu-kvm) and the KVM
kernel modules may change in future updates. Using the latest upstream qemu-kvm package is
unsupported due to ABI differences.
• Devices using the qlge driver cannot be assigned to a KVM guest using KVM's PCI Device Driver
(BZ#507689)
assignment.
• the use of the qcow2 disk image format with KVM is considered a Technology Preview.
97
(BZ#517880)
• 64-bit versions of Windows 7 do not have support for the AC'97 Audio Codec. Consequently, the
virtualized sound device Windows 7 kvm guests will not function.
• Hotplugging emulated devices after migration may result in the virtual machine crashing after a
reboot or the devices no longer being visible.
• Windows 2003 32-bit guests with more than 4GB of RAM may crash on reboot with the default
qemu-kvm CPU settings. To work around this issue, configure a different CPU model on the
management interface.
• The KVM modules from the kmod-kvm package do not support kernels prior to version
2.6.18-159.el5. Error messages similar to the following will be returned if attempting to install these
modules on older kernels:
FATAL: Error inserting kvm_intel
(/lib/modules/2.6.18-155.el5/weak-updates/kmod-kvm/kvm-intel.ko): Unknown
symbol in module, or unknown parameter (see dmesg)
101
(BZ#509361)
320
93
(BZ#515549)
96
(BZ#507191)
100
(BZ#516762)
95
(BZ#563122
99
98
)