Matt T. Yourst
2006-Mar-30 00:35 UTC
[Xen-devel] [PATCH] Make cpufreq drivers (powernow-k8) Xen-compatible
Hi, The attached patch fixes the powernow-k8 cpufreq module so it uses DOM0_OP_MSR to properly set the K8 voltage/frequency MSRs when running under Xen, instead of directly using rdmsr/wrmsr, which were being silently ignored. The patch will eliminate syslog messages like this: kernel: powernow-k8: transition frequency failed kernel: powernow-k8: fid trans failed, fid 0xa, curr 0x0 I''m now successfully using Xen on my Athlon 64 laptop with this patch, and the CPU really changes frequency/voltage, instead of just pretending to do so when wrmsr was ignored without the patch. Presently it only works on single CPU machines, but you could readily extend it to many cores by properly setting the cpumask vector before calling DOM0_OP_MSR (note that cpufreq itself still seems to have bugs on the dual-core Opterons, so that may not be relevant right now). The xen_access_msr() function can be easily pasted into the other cpufreq drivers, but since I have an Athlon 64, that''s the only one I patched. [I''m not on the list, please forward replies]. - Matt Yourst ------------------------------------------------------- Matt T. Yourst yourst@cs.binghamton.edu Binghamton University, Department of Computer Science ------------------------------------------------------- _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel