The optional object _CPC declares an interface that allows OSPM to
transition the processor into a performance state based on a continuous
range of allowable values.
It is associated with HWP on intel CPUs. Although Linux intel_pstate driver
can have its performance managing abilities without _CPC, it may still
need this _CPC table to implement some features such as providing the kernel
multi-core scheduler with core priority info.
As currently we are giving guests a vHWP interface for the multi-core
scheduler, this patch adds _CPC to the guest ACPI. _CPC is written only
when the hypervisor decides the guest should have vHWP, using the
existing pm hypercall ACRN_PMCMD_GET_PX_CNT. The idea is:
- If the VM supports vHWP, then the guest is having continuous p-state.
Thus it doesn't have a specific px_cnt. The hypercall returns success
and px_cnt = 0.
- If the VM's p-state is hidden or hv doesn't have its p-state info,
the hypercall returns fail.
Tracked-On: #8414
Signed-off-by: Wu Zhou <wu.zhou@intel.com>
Reviewed-by: Jian Jun Chen <jian.jun.chen@intel.com>
8c38cd5734