It should be kHz not khz. - msr, (u32)khz / 1000); + msr, (u32)kHz / 1000);
On Thu, Aug 9, 2012 at 2:53 PM, Avi Kivity <a...@redhat.com> wrote: > On 08/09/2012 02:57 PM, Gerd Hoffmann wrote: >> Use kvmclock for tsc calibration when running on kvm. Without this the >> tsc frequency calibrated by seabios can be *way* off in case the virtual >> machine is booted on a loaded host. I've seen seabios calibrating 27 >> instead of ca. 2800 MHz, resulting in timeouts being to short by factor >> 100. Which in turn leads to disk I/O errors due to timeouts, especially >> as I/O requests tend to take a bit longer than usual on a loaded box ... > >> + >> +struct pvclock_vcpu_time_info { >> + u32 version; >> + u32 pad0; >> + u64 tsc_timestamp; >> + u64 system_time; >> + u32 tsc_to_system_mul; >> + s8 tsc_shift; >> + u8 flags; >> + u8 pad[2]; >> +} PACKED; >> + >> + >> +u64 kvm_tsc_khz(void) >> +{ >> + u32 eax, ebx, ecx, edx, msr; >> + struct pvclock_vcpu_time_info time; >> + u32 addr = (u32)(&time); >> + u64 khz; >> + >> + /* check presence and figure msr number */ >> + cpuid(KVM_CPUID_FEATURES, &eax, &ebx, &ecx, &edx); >> + if (eax & KVM_FEATURE_CLOCKSOURCE2) { >> + msr = MSR_KVM_SYSTEM_TIME_NEW; >> + } else if (eax & KVM_FEATURE_CLOCKSOURCE) { >> + msr = MSR_KVM_SYSTEM_TIME; >> + } else { >> + return 0; >> + } >> + >> + /* ask kvm hypervisor to fill struct */ >> + memset(&time, 0, sizeof(time)); >> + wrmsr(msr, addr | 1); > > How can this work? There is a 64-byte alignment requirement. > >> + wrmsr(msr, 0); >> + if (time.version < 2 || time.tsc_to_system_mul == 0) >> + return 0; >> + >> + /* go figure tsc frequency */ >> + khz = pvclock_tsc_khz(&time); >> + dprintf(1, "Using kvmclock, msr 0x%x, tsc %d MHz\n", >> + msr, (u32)khz / 1000); >> + return khz; > > That's a meaningless number. You can be migrated to a cpu or a machine > with very different tsc. > > You want accurate time on kvm, don't use the tsc. > > > -- > error compiling committee.c: too many arguments to function > > _______________________________________________ > SeaBIOS mailing list > SeaBIOS@seabios.org > http://www.seabios.org/mailman/listinfo/seabios _______________________________________________ SeaBIOS mailing list SeaBIOS@seabios.org http://www.seabios.org/mailman/listinfo/seabios