[Xen-devel] Writing MSRs from Domain0

[Holger Steinhaus <hsteinhaus@xxxxxx>]

Hello,

I recently tried Xen 3.0.3-testing on my 2x Opteron-244 SMP machine.
Everything works well exept one detail, which is not unimportant to me:
the powernow-k8 driver fails to switch frequencies. A closer look on the
powernow-k8 source reveals, that some MSR write operations seem to be
without any effect. A rdmsr() before and after the  wrmsr() call reveals
that no real change on the register ocurrs.

An older PowerNow patch from this list emulates MSR writes by DOM0_MSR
hypercalls, but this call seems to be abandoned some time ago. Other
routines in the kernel simply employ the rdmsr()/wrmsr() macros from the
Linux kernel, as the current PowerNow drivers does. Whats the correct
Xen-like way to maniputate a MSR from a Domain0?

Regards,
  Holger

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