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[NTOS:KE/x64] Calculate the CPU frequency on AMD64

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This should be performed early enough before CM initialization,
but after the TSC has been initialized and calibrated by HAL.

Based on existing i386 kiinit code. CORE-17971 CORE-14922
This commit is contained in:
Stanislav Motylkov 2023-07-12 15:28:48 +03:00
parent 1896383eb0
commit e2a587c2ef
1 changed files with 86 additions and 0 deletions
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86
ntoskrnl/ke/amd64/krnlinit.c
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@ -30,6 +30,89 @@ KiInitializeKernel(IN PKPROCESS InitProcess,
IN PLOADER_PARAMETER_BLOCK LoaderBlock);
CODE_SEG("INIT")
VOID
KiCalculateCpuFrequency(
IN PKPRCB Prcb)
{
if (Prcb->FeatureBits & KF_RDTSC)
{
ULONG Sample = 0;
CPU_INFO CpuInfo;
KI_SAMPLE_MAP Samples[10];
PKI_SAMPLE_MAP CurrentSample = Samples;
/* Start sampling loop */
for (;;)
{
/* Do a dummy CPUID to start the sample */
KiCpuId(&CpuInfo, 0);
/* Fill out the starting data */
CurrentSample->PerfStart = KeQueryPerformanceCounter(NULL);
CurrentSample->TSCStart = __rdtsc();
CurrentSample->PerfFreq.QuadPart = -50000;
/* Sleep for this sample */
KeStallExecutionProcessor(CurrentSample->PerfFreq.QuadPart * -1 / 10);
/* Do another dummy CPUID */
KiCpuId(&CpuInfo, 0);
/* Fill out the ending data */
CurrentSample->PerfEnd =
KeQueryPerformanceCounter(&CurrentSample->PerfFreq);
CurrentSample->TSCEnd = __rdtsc();
/* Calculate the differences */
CurrentSample->PerfDelta = CurrentSample->PerfEnd.QuadPart -
CurrentSample->PerfStart.QuadPart;
CurrentSample->TSCDelta = CurrentSample->TSCEnd -
CurrentSample->TSCStart;
/* Compute CPU Speed */
CurrentSample->MHz = (ULONG)((CurrentSample->TSCDelta *
CurrentSample->
PerfFreq.QuadPart + 500000) /
(CurrentSample->PerfDelta *
1000000));
/* Check if this isn't the first sample */
if (Sample)
{
/* Check if we got a good precision within 1MHz */
if ((CurrentSample->MHz == CurrentSample[-1].MHz) ||
(CurrentSample->MHz == CurrentSample[-1].MHz + 1) ||
(CurrentSample->MHz == CurrentSample[-1].MHz - 1))
{
/* We did, stop sampling */
break;
}
}
/* Move on */
CurrentSample++;
Sample++;
if (Sample == RTL_NUMBER_OF(Samples))
{
/* No luck. Average the samples and be done */
ULONG TotalMHz = 0;
while (Sample--)
{
TotalMHz += Samples[Sample].MHz;
}
CurrentSample[-1].MHz = TotalMHz / RTL_NUMBER_OF(Samples);
DPRINT1("Sampling CPU frequency failed. Using average of %lu MHz\n", CurrentSample[-1].MHz);
break;
}
}
/* Save the CPU Speed */
Prcb->MHz = CurrentSample[-1].MHz;
}
}
VOID
NTAPI
KiInitializeHandBuiltThread(
@ -105,6 +188,9 @@ KiSystemStartupBootStack(VOID)
}
}
/* Calculate the CPU frequency */
KiCalculateCpuFrequency(Prcb);
/* Raise to Dispatch */
KfRaiseIrql(DISPATCH_LEVEL);