Description of problem: no speedstep support with xen Version-Release number of selected component (if applicable): xen-3.0.3-1.fc6 kernel-xen-2.6.18-1.2869.fc6 cpuspeed-1.2.1-1.46.fc6 CPU: Intel(R) Core(TM)2 CPU T7600 @ 2.33GHz Machine: Dell Precision Mobile Workstation M90 How reproducible: always Steps to Reproduce: 1. Boot into kernel-xen 2. Check /sys/devices/system/cpu/cpu0/cpufreq 3. it is not present Actual results: no speedstep Expected results: The centrino speedstep should be available due to a patch by Matt Yourst http://lkml.org/lkml/2006/4/14/151 Additional info: There is a release note in cpuspeed-1.2.1-1.43 http://fedoranews.org/cms/node/2386 that it does not start on xen kernels. If xen kernels should provide speedstep, this should be re-enabled as well.
The reason that frequency scaling is disabled is not because speedstep doesn't work under Xen. It *does* work, if enabled --- but it completely fails to take account of activity in domains other than the host dom0. So if you have a guest domU busy on the machine and dom0 is idle, frequency scaling will slow the host down to its slowest setting. In the future we hope for this to be fixed upstream, but we have no plans to address it in FC-6 at this time.
Sorry, I forgot a diagnostic message. The FC6 xen kernel does not load the module acpi_cpufreq during boot and is therefore not able to set up speedstep. FATAL: module acpi_cpufreq not found Please advise how I can load this module under xen, since you mention "it *does* work". The reason is: on dual core laptops, missing speedstep is annoying since energy consumption and heat is significantly higher. I think slowing down the whole activity of all xen domains is the expected behavior and I could live with only accounting of cpu activity in dom0.