| #include "libcflat.h" |
| #include "processor.h" |
| |
| int main(void) |
| { |
| u64 t1, t2, t3, t4, t5; |
| u64 est_delta_time; |
| |
| if (this_cpu_has(X86_FEATURE_TSC_ADJUST)) { // MSR_IA32_TSC_ADJUST Feature is enabled? |
| report(rdmsr(MSR_IA32_TSC_ADJUST) == 0x0, |
| "MSR_IA32_TSC_ADJUST msr initialization"); |
| t3 = 100000000000ull; |
| t1 = rdtsc(); |
| wrmsr(MSR_IA32_TSC_ADJUST, t3); |
| t2 = rdtsc(); |
| report(rdmsr(MSR_IA32_TSC_ADJUST) == t3, |
| "MSR_IA32_TSC_ADJUST msr read / write"); |
| report((t2 - t1) >= t3, |
| "TSC adjustment for MSR_IA32_TSC_ADJUST value"); |
| t3 = 0x0; |
| wrmsr(MSR_IA32_TSC_ADJUST, t3); |
| report(rdmsr(MSR_IA32_TSC_ADJUST) == t3, |
| "MSR_IA32_TSC_ADJUST msr read / write"); |
| t4 = 100000000000ull; |
| t1 = rdtsc(); |
| wrtsc(t4); |
| t2 = rdtsc(); |
| t5 = rdmsr(MSR_IA32_TSC_ADJUST); |
| // est of time between reading tsc and writing tsc, |
| // (based on MSR_IA32_TSC_ADJUST msr value) should be small |
| est_delta_time = t4 - t5 - t1; |
| // arbitray 2x latency (wrtsc->rdtsc) threshold |
| report(est_delta_time <= (2 * (t2 - t4)), |
| "MSR_IA32_TSC_ADJUST msr adjustment on tsc write"); |
| } |
| else { |
| report_pass("MSR_IA32_TSC_ADJUST feature not enabled"); |
| } |
| return report_summary(); |
| } |