On Thu, 28 Jun 2018, Peter Zijlstra wrote: > 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. True. > Calibrating against a virtual PIT/HPET/PMTIMER is utterly pointless. It kinda works :) > > 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. As I figured out now that's only part of the picture. We also need to do that past x86_dtb_init() because early_quirks() and the early acpi/sfi/dtb stuff needs to be completed before it makes sense to access hpet. But at that point we also have the PMTIMER info. > 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. Right. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
