Oracle Audio Technologies E10898-02 manual Setting the Guest’s Clock, Wallclock Time Skew Problems

Mouse Pointer Tracking Problems

E.6 Setting the Guest’s Clock

Paravirtualized guests may perform their own system clock management, for example, using the NTPD (Network Time Protocol daemon), or the hypervisor may perform system clock management for all guests.

You can set paravirtualized guests to manage their own system clocks by setting the xen.independent_wallclock parameter to 1 in the /etc/sysctl.conf file. For example

"xen.independent_wallclock = 1"

If you want to set the hypervisor to manage paravirtualized guest system clocks, set xen.independent_wallclock to 0. Any attempts to set or modify the time in a guest will fail.

You can temporarily override the setting in the /proc file. For example

"echo 1 > /proc/sys/xen/independent_wallclock"

Note: This setting does not apply to hardware virtualized guests.

E.7 Wallclock Time Skew Problems

Oracle VM Release 2.1.1 introduces the use of the timer_mode parameter for hardware virtualized guests. This parameter, when properly applied, can reduce or even eliminate problems with wallclock time skew in most hardware virtualized guests. Wallclock time skew problems do not occur in paravirtualized guests.

Since the application of the correct value of the timer_mode parameter can be difficult to determine, you can pass the os-typeand os-variantcommand-line switches to virt-install to select the best timer_mode value for the guest operating system. When you use these virt-install parameters, the correct timer_mode value is automatically added to the guest configuration file. For example, to create an Oracle Enterprise Linux 5 64-bit guest, add the following to the virt-install command-line:

virt-install --hvm ... --os-type=linux --os-variant=el5_64 ...

For best results, additional parameters may be needed in the boot loader (grub.conf) configuration file for certain operating system variants after the guest is installed. Specifically, for optimal clock accuracy, Linux guest boot parameters should be specified to ensure that the pit clock source is utilized. Adding clock=pit nohpet nopmtimer for most guests will result in the selection of pit as the clock source for the guest. Published templates for Oracle VM will include these additional parameters.

Proper maintenance of virtual time can be tricky. The various parameters provide tuning for virtual time management and supplement, but do not replace, the need for an ntp time service running within guest. Ensure that the ntpd service is running and that the /etc/ntpd.conf configuration file is pointing to valid time servers.

E.8 Mouse Pointer Tracking Problems

If your mouse pointer fails to track your cursor in a VNC Viewer session in a hardware virtualized guest, add the following to the Oracle VM Server configuration file located at /etc/xen/xend-config.sxp to force the device model to use absolute (tablet) coordinates:

usbdevice='tablet'

Troubleshooting E-5