Installation guide

If any output is given your CPU has the co nstant_tsc bit. If no output is given follow the
instructions below.
14 .1.1. Configuring host s wit hout a const ant T ime St amp Count er
Systems without a constant TSC frequency cannot use the TSC as a clock source for virtual
machines, and require additional configuration. Power management features interfere with accurate
time keeping and must be disabled for guest virtual machines to accurately keep time with KVM.
Important
These instructions are for AMD revision F CPUs only.
If the CPU lacks the co nstant_tsc bit, disable all power management features (BZ #513138). Each
system has several timers it uses to keep time. The TSC is not stable on the host, which is sometimes
caused by cpufreq changes, deep C state, or migration to a host with a faster TSC. Deep C sleep
states can stop the TSC. To prevent the kernel using deep C states append
pro cesso r. max_cstate= 1 to the kernel boot options in the g rub. co nf file on the host:
title Red Hat Enterprise Linux (2.6.32-330.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-330.x86_64 ro root=/dev/VolGroup00/LogVol00 rhgb
quiet \
processor.max_cstate=1
Disable cpufreq (only necessary on hosts without the co nstant_tsc) by editing the
/etc/sysco nfi g /cpuspeed configuration file and change the MIN_SP EED and MAX_SP EED
variables to the highest frequency available. Valid limits can be found in the
/sys/d evi ces/system/cpu/cpu*/cpufreq /scal ing _avai l abl e_freq uenci es files.
14 .2. Required paramet ers for Red Hat Ent erprise Linux guest s
For certain Red Hat Enterprise Linux guest virtual machines, additional kernel parameters are
required. These parameters can be set by appending them to the end of the /kernel line in the
/bo o t/g rub/g rub. co nf file of the guest virtual machine.
The table below lists versions of Red Hat Enterprise Linux and the parameters required on the
specified systems.
T ab le 14 .1. Kern el p aramet er req u iremen t s
Red Hat En terp rise Lin u x versio n Ad d it io nal g u est kern el p aramet ers
6.0 AMD64/Intel 64 with the para-virtualized
clock
Additional parameters are not required
6.0 AMD64/Intel 64 without the para-virtualized
clock
notsc lpj=n
5.5 AMD64/Intel 64 with the para-virtualized
clock
Additional parameters are not required
5.5 AMD64/Intel 64 without the para-virtualized
clock
notsc lpj=n
Red Hat Ent erp rise Linux 6 Virt ualiz at ion Host Configurat ion and G uest Inst allat ion G uide
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