Oracle Audio Technologies E10898-02 ユーザーズマニュアル

Mouse Pointer Tracking Problems

Troubleshooting

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"

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-type

 and 

os-variant

 command-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.

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'

This setting does not apply to hardware virtualized guests.