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106 lines
2.8 KiB
C
106 lines
2.8 KiB
C
/*
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* COPYRIGHT: See COPYING.ARM in the top level directory
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* PROJECT: ReactOS UEFI Boot Library
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* FILE: boot/environ/lib/platform/time.c
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* PURPOSE: Boot Library Time Management Routines
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* PROGRAMMER: Alex Ionescu (alex.ionescu@reactos.org)
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*/
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/* INCLUDES ******************************************************************/
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#include "bl.h"
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/* DATA VARIABLES ************************************************************/
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ULONGLONG BlpTimePerformanceFrequency;
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/* FUNCTIONS *****************************************************************/
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NTSTATUS
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BlpTimeMeasureTscFrequency (
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VOID
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)
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{
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ULONG Count;
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INT CpuInfo[4];
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ULONGLONG TimeStamp1, TimeStamp2, Delta;
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/* Check if the ISVM bit it set, meaning we're in a hypervisor */
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__cpuid(CpuInfo, 1);
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Count = CpuInfo[2] & 0x80000000 ? 10 : 1;
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/* Loop trying to get an accurate TSC */
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do
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{
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/* Stall for 1us and get count 1 */
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EfiStall(1);
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TimeStamp1 = __rdtsc();
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/* Stall for 1000us and get count 2*/
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EfiStall(1000);
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TimeStamp2 = __rdtsc();
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/* Stall for 9000us and get the difference */
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EfiStall(9000);
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Delta = __rdtsc() - TimeStamp2;
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/* Keep going as long as the TSC is fluctuating */
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--Count;
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} while (((TimeStamp2 - TimeStamp1) > Delta) && (Count));
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/* Set the frequency based on the two measurements we took */
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BlpTimePerformanceFrequency = 125 * (Delta - (TimeStamp2 - TimeStamp1)) & 0x1FFFFFFFFFFFFFF;
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return STATUS_SUCCESS;
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}
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NTSTATUS
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BlpTimeCalibratePerformanceCounter (
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VOID
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)
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{
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INT CpuInfo[4];
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/* Check if the ISVM bit it set, meaning we're in a hypervisor */
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__cpuid(CpuInfo, 1);
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if (CpuInfo[2] & 0x80000000)
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{
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/* Get the Hypervisor Identification Leaf */
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__cpuid(CpuInfo, 0x40000001);
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/* Is this Hyper-V? */
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if (CpuInfo[0] == '1#vH')
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{
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/* Get the Hypervisor Feature Identification Leaf */
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__cpuid(CpuInfo, 0x40000003);
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/* Check if HV_X64_MSR_REFERENCE_TSC is present */
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if (CpuInfo[3] & 0x100)
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{
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/* Read the TSC frequency from the MSR */
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BlpTimePerformanceFrequency = __readmsr(0x40000022);
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EfiPrintf(L"Using Hyper-V frequency as: %I64d\r\n", BlpTimePerformanceFrequency);
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return STATUS_SUCCESS;
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}
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}
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}
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/* On other systems, compute it */
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return BlpTimeMeasureTscFrequency();
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}
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ULONGLONG
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BlTimeQueryPerformanceCounter (
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_Out_opt_ PLARGE_INTEGER Frequency
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)
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{
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/* Check if caller wants frequency */
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if (Frequency)
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{
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/* Return it */
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Frequency->QuadPart = BlpTimePerformanceFrequency;
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}
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/* Return the TSC value */
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return __rdtsc();
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};
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