On Wed, Feb 07, 2024, Xin Li wrote: > Clear FRED VM entry/exit controls when initializing a vCPU, and set > these controls only if FRED is enumerated after set CPUID. > > FRED VM entry/exit controls need to be set to establish context > sufficient to support FRED event delivery immediately after VM entry > and exit. However it is not required to save/load FRED MSRs for > a non-FRED guest, which aren't supposed to access FRED MSRs. Does this actually provide a measurable performance boost? If not, just do the unnecessary load/store on entry/exit. Generally speaking, the only time KVM dynamically toggles entry/exit controls is when KVM wants to run the guest with a host value, e.g. with the host's PERF_GLOBAL_CTRL.
