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 avi@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
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