time.c File Reference

#include "bl.h"

Include dependency graph for time.c:

Go to the source code of this file.

Functions
NTSTATUS	BlpTimeMeasureTscFrequency (VOID)
NTSTATUS	BlpTimeCalibratePerformanceCounter (VOID)
ULONGLONG	BlTimeQueryPerformanceCounter (_Out_opt_ PLARGE_INTEGER Frequency)

Variables
ULONGLONG	BlpTimePerformanceFrequency

Function Documentation

BlpTimeCalibratePerformanceCounter()

NTSTATUS BlpTimeCalibratePerformanceCounter

(

VOID

)

Definition at line 62 of file time.c.

{
#if defined(_M_IX86) || defined(_M_X64)
    INT CpuInfo[4];
 
    /* Check if the ISVM bit it set, meaning we're in a hypervisor */
    __cpuid(CpuInfo, 1);
    if (CpuInfo[2] & 0x80000000)
    {
        /* Get the Hypervisor Identification Leaf */
        __cpuid(CpuInfo, 0x40000001);
 
        /* Is this Hyper-V? */
        if (CpuInfo[0] == '1#vH')
        {
            /* Get the Hypervisor Feature Identification Leaf */
            __cpuid(CpuInfo, 0x40000003);
 
            /* Check if HV_X64_MSR_REFERENCE_TSC is present */
            if (CpuInfo[3] & 0x100)
            {
                /* Read the TSC frequency from the MSR */
                BlpTimePerformanceFrequency = __readmsr(0x40000022);
                return STATUS_SUCCESS;
            }
        }
    }
 
    /* On other systems, compute it */
    return BlpTimeMeasureTscFrequency();
#else
    EfiPrintf(L"BlpTimeCalibratePerformanceCounter not implemented for this platform.\r\n");
    return STATUS_NOT_IMPLEMENTED;
#endif
}

Referenced by InitializeLibrary().

BlpTimeMeasureTscFrequency()

NTSTATUS BlpTimeMeasureTscFrequency

(

VOID

)

Definition at line 20 of file time.c.

{
#if defined(_M_IX86) || defined(_M_X64)
    ULONG Count;
    INT CpuInfo[4];
    ULONGLONG TimeStamp1, TimeStamp2, Delta;
 
    /* Check if the ISVM bit it set, meaning we're in a hypervisor */
    __cpuid(CpuInfo, 1);
    Count = CpuInfo[2] & 0x80000000 ? 10 : 1;
 
    /* Loop trying to get an accurate TSC */
    do
    {
        /* Stall for 1us and get count 1 */
        EfiStall(1);
        TimeStamp1 = __rdtsc();
 
        /* Stall for 1000us and get count 2*/
        EfiStall(1000);
        TimeStamp2 = __rdtsc();
 
        /* Stall for 9000us and get the difference */
        EfiStall(9000);
        Delta = __rdtsc() - TimeStamp2;
 
        /* Keep going as long as the TSC is fluctuating */
        --Count;
    } while (((TimeStamp2 - TimeStamp1) > Delta) && (Count));
 
    /* Set the frequency based on the two measurements we took */
    BlpTimePerformanceFrequency = 125 * (Delta - (TimeStamp2 - TimeStamp1)) & 0x1FFFFFFFFFFFFFF;
    return STATUS_SUCCESS;
#else
    EfiPrintf(L"BlpTimeMeasureTscFrequency not implemented for this platform.\r\n");
    return STATUS_NOT_IMPLEMENTED;
#endif
}

Referenced by BlpTimeCalibratePerformanceCounter().

BlTimeQueryPerformanceCounter()

ULONGLONG BlTimeQueryPerformanceCounter

(

_Out_opt_ PLARGE_INTEGER

Frequency

)

Definition at line 101 of file time.c.

{
#if defined(_M_IX86) || defined(_M_X64)
    /* Check if caller wants frequency */
    if (Frequency)
    {
        /* Return it */
        Frequency->QuadPart = BlpTimePerformanceFrequency;
    }
 
    /* Return the TSC value */
    return __rdtsc();
#else
    EfiPrintf(L"BlTimeQueryPerformanceCounter not implemented for this platform.\r\n");
    return 0;
#endif
};

Referenced by BlImgLoadBootApplication().

Variable Documentation

BlpTimePerformanceFrequency

ULONGLONG BlpTimePerformanceFrequency

Definition at line 15 of file time.c.

Referenced by BlpTimeCalibratePerformanceCounter(), BlpTimeMeasureTscFrequency(), BlTimeQueryPerformanceCounter(), and InitializeLibrary().