On Thu, Jun 28, 2018 at 12:43:59PM +0200, Thomas Gleixner wrote: > init_hypervisor_platform() > vmware: > Retrieves frequency and store it for the > calibration function > > khz = vmware_get_khz_magic() > vmware_tsc_khz = khz > calibrate_cpu = vmware_get_tsc_khz > calibrate_tsc = vmware_get_tsc_khz > preset_lpj(khz) > > hyperv: > if special hyperv MSRs are available: > > calibrate_cpu = hv_get_tsc_khz > calibrate_tsc = hv_get_tsc_khz > > MSR is readable already in this function > > jailhouse: > > Frequency is available in this function and store > in a variable for the calibration function > > calibrate_cpu = jailhouse_get_tsc > calibrate_tsc = jailhouse_get_tsc > > ... > > kvmclock_init() > > if (magic_conditions) > calibrate_tsc = kvm_get_tsc_khz > calibrate_cpu = kvm_get_tsc_khz > > kvm_get_preset_lpj() > khz = kvm_get_tsc_khz() > preset_lpj(khz);
Note that all these which get TSC values from a HV _should_ set X86_FEATURE_TSC_KNOWN_FREQ to avoid the late recalibrate. Calibrating against a virtual PIT/HPET/PMTIMER is utterly pointless. > The generic initilizaiton does everything twice, which makes no sense, > except for the unlikely case were no fast functions are available and the > quick PIT calibration fails (PMTIMER/HPET) are not available in early > calibration. HPET Incomplete; but I suspect you want to talk about how we can make HPET available early by putting it in a fixmap. And only if we fail, do we at a later stage try again using PMTIMER. Currently it all works by accident, since !hpet and acpi_pm_read_early() returns 0, but really we should not be running the fallback crap at all that early.
