reactos/boot/environ/lib/platform/time.c

   1 /*
   2  * COPYRIGHT:       See COPYING.ARM in the top level directory
   3  * PROJECT:         ReactOS UEFI Boot Library
   4  * FILE:            boot/environ/lib/platform/time.c
   5  * PURPOSE:         Boot Library Time Management Routines
   6  * PROGRAMMER:      Alex Ionescu (alex.ionescu@reactos.org)
   7  */
   8
   9 /* INCLUDES ******************************************************************/
  10
  11 #include "bl.h"
  12
  13 /* DATA VARIABLES ************************************************************/
  14
  15 ULONGLONG BlpTimePerformanceFrequency;
  16
  17 /* FUNCTIONS *****************************************************************/
  18
  19 NTSTATUS
  20 BlpTimeMeasureTscFrequency (
  21     VOID
  22     )
  23 {
  24     ULONG Count;
  25     INT CpuInfo[4];
  26     ULONGLONG TimeStamp1, TimeStamp2, Delta;
  27
  28     /* Check if the ISVM bit it set, meaning we're in a hypervisor */
  29     __cpuid(CpuInfo, 1);
  30     Count = CpuInfo[2] & 0x80000000 ? 10 : 1;
  31
  32     /* Loop trying to get an accurate TSC */
  33     do
  34     {
  35         /* Stall for 1us and get count 1 */
  36         EfiStall(1);
  37         TimeStamp1 = __rdtsc();
  38
  39         /* Stall for 1000us and get count 2*/
  40         EfiStall(1000);
  41         TimeStamp2 = __rdtsc();
  42
  43         /* Stall for 9000us and get the difference */
  44         EfiStall(9000);
  45         Delta = __rdtsc() - TimeStamp2;
  46
  47         /* Keep going as long as the TSC is fluctuating */
  48         --Count;
  49     } while (((TimeStamp2 - TimeStamp1) > Delta) && (Count));
  50
  51     /* Set the frequency based on the two measurements we took */
  52     BlpTimePerformanceFrequency = 125 * (Delta - (TimeStamp2 - TimeStamp1)) & 0x1FFFFFFFFFFFFFF;
  53     return STATUS_SUCCESS;
  54 }
  55
  56 NTSTATUS
  57 BlpTimeCalibratePerformanceCounter (
  58     VOID
  59     )
  60 {
  61     INT CpuInfo[4];
  62
  63     /* Check if the ISVM bit it set, meaning we're in a hypervisor */
  64     __cpuid(CpuInfo, 1);
  65     if (CpuInfo[2] & 0x80000000)
  66     {
  67         /* Get the Hypervisor Identification Leaf */
  68         __cpuid(CpuInfo, 0x40000001);
  69
  70         /* Is this Hyper-V? */
  71         if (CpuInfo[0] == '1#vH')
  72         {
  73             /* Get the Hypervisor Feature Identification Leaf */
  74             __cpuid(CpuInfo, 0x40000003);
  75
  76             /* Check if HV_X64_MSR_REFERENCE_TSC is present */
  77             if (CpuInfo[3] & 0x100)
  78             {
  79                 /* Read the TSC frequency from the MSR */
  80                 BlpTimePerformanceFrequency = __readmsr(0x40000022);
  81                 EfiPrintf(L"Using Hyper-V frequency as: %I64d\r\n", BlpTimePerformanceFrequency);
  82                 return STATUS_SUCCESS;
  83             }
  84         }
  85     }
  86
  87     /* On other systems, compute it */
  88     return BlpTimeMeasureTscFrequency();
  89 }
  90
  91 ULONGLONG
  92 BlTimeQueryPerformanceCounter (
  93     _Out_opt_ PLARGE_INTEGER Frequency
  94     )
  95 {
  96     /* Check if caller wants frequency */
  97     if (Frequency)
  98     {
  99         /* Return it */
 100         Frequency->QuadPart = BlpTimePerformanceFrequency;
 101     }
 102
 103     /* Return the TSC value */
 104     return __rdtsc();
 105 };