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Intel/AMD Speedstep/PowerNow support
The following patch  adds Speedstep/PowerNow support in NetBSD dom0.
As Xen 3 traps MSR instructions, I just made some adjustments in the
files.xen/compat files and config(5) so that the operations are
avalaible within dom0.
Please note that, depending on the version of the hypervisor you are
using, some instructions won't be handled by Xen. In that case, they
will result in a NOOP, and the error will be logged by xen dmesg.
=> with Xen 3.1, rdmsr() should always succeed, but some wrmsr() will
fail with a "Domain attempted to WRMSR xxx from yyy to zzz". This means
that this patch allows you to get the CPU current frequency (through
machdep.est.frequency.current), but you cannot set it through
=> with Xen 3.3, provided you passed "cpufreq=dom0-kernel" as parameter
to Xen kernel during boot, you can change CPU speed the same way as you
would do with a GENERIC kernel.
Compiled and tested for Speedstep under i386 for XEN3_DOM0 and
XEN3PAE_DOM0 kernels. amd64 and PowerNow were only compile tested (no
Current patch mimics GENERIC, and enables Speedstep/PowerNow by default.
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