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     EarlyPrint(L"Computed frequency as: %I64d\n", BlpTimePerformanceFrequency);
  54     return STATUS_SUCCESS;
  55 }
  56
  57 NTSTATUS
  58 BlpTimeCalibratePerformanceCounter (
  59     VOID
  60     )
  61 {
  62     INT CpuInfo[4];
  63
  64     /* Check if the ISVM bit it set, meaning we're in a hypervisor */
  65     __cpuid(CpuInfo, 1);
  66     if (CpuInfo[2] & 0x80000000)
  67     {
  68         /* Get the Hypervisor Identification Leaf */
  69         __cpuid(CpuInfo, 0x40000001);
  70
  71         /* Is this Hyper-V? */
  72         if (CpuInfo[0] == '1#vH')
  73         {
  74             /* Get the Hypervisor Feature Identification Leaf */
  75             __cpuid(CpuInfo, 0x40000003);
  76
  77             /* Check if HV_X64_MSR_REFERENCE_TSC is present */
  78             if (CpuInfo[3] & 0x100)
  79             {
  80                 /* Read the TSC frequency from the MSR */
  81                 BlpTimePerformanceFrequency = __readmsr(0x40000022);
  82                 EarlyPrint(L"Using frequency as: %I64d\n", BlpTimePerformanceFrequency);
  83                 return STATUS_SUCCESS;
  84             }
  85         }
  86     }
  87
  88     /* On other systems, compute it */
  89     return BlpTimeMeasureTscFrequency();
  90 }