On 18/07/2023 2:17 pm, Simon Gaiser wrote: > Since it's limited to the hardware domain it should be safe and it's > very useful to have access to this directly in dom0 when debugging power > related things for example S0ix.
You need a SoB. But, this is an area there things are subtly broken. For package-scope MSRs on single socket systems (which does include client systems), then this happens to function. It does not function for core-scoped MSRs, or at all in a multi-socket system. In such scenarios, dom0 can be rescheduled to a CPU in a different scope while it thinks it is sampling a single scope. This is one of the areas where dom0 and Xen end up fighting over the system. I agree that we want some way for dom0 to get this information, but I'm afraid it's not as simple as just permitting access to the MSRs like this. ~Andrew
