On Mon, Sep 26, 2022 at 1:50 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Fri, Sep 23, 2022, Jim Mattson wrote: > > In the default configuration, the guest TSC frequency is the same as > > the host TSC frequency. Similarly, the maximum frequency of the > > virtual CPU is the same as the maximum frequency of the physical > > CPU. > > Under the hood, yes, but after the VM is migrated, isn't it possible that the > host frequencies are completely disjoint from the frequencies that are enumerated > to the guest? > > > Also, the bus (reference) frequency of the virtual CPU matches > > that of the physical CPU. > > > > Pass this information directly from host CPUID.16H to guest CPUID.16H > > in KVM_GET_SUPPORTED_CPUID. > > What about "solving" this via documentation, same as CPUID.15H? If the API were > KVM_GET_DEFAULT_CPUID, then enumerating host properties makes sense, but from a > very pedantic point of view, the "supported" frequencies are just about anything. Fair enough. Userspace will just have to figure out how to populate this leaf on its own (or leave it blank). > Somewhat of a moot point, as the leaf comes with "informational only" disclaimer. > > The returned information should not be used for any other purpose as the returned > information does not accurately correlate to information / counters returned by > other processor interfaces.
