[telemetry] Read MSRs from a separate privileged process.

tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py

Index: tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py
diff --git a/tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py b/tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py
index 80b9f5f26838a4f67e879d172f7c0f0a2fbb27c1..038346dfebad4fa71614f4f346a388ca514833f9 100644
--- a/tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py
+++ b/tools/telemetry/telemetry/core/platform/power_monitor/msr_power_monitor.py
@@ -2,19 +2,12 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import atexit
-import ctypes
 import logging
-import os
 import platform
 import re
-import sys
-import zipfile
 
 from telemetry import decorators
 from telemetry.core.platform import power_monitor
-from telemetry.util import cloud_storage
-from telemetry.util import path
 
 
 MSR_RAPL_POWER_UNIT = 0x606
@@ -26,100 +19,6 @@ IA32_PACKAGE_THERM_STATUS = 0x1b1
 IA32_TEMPERATURE_TARGET = 0x1a2
 
 
-WINRING0_STATUS_MESSAGES = (
-    'No error',
-    'Unsupported platform',
-    'Driver not loaded. You may need to run as Administrator',
-    'Driver not found',
-    'Driver unloaded by other process',
-    'Driver not loaded because of executing on Network Drive',
-    'Unknown error',
-)
-
-
-# The DLL initialization is global, so put it in a global variable.
-_winring0 = None
-
-
-class WinRing0Error(OSError):
-  pass
-
-
-@decorators.Cache
-def WinRing0Path():
-  python_is_64_bit = sys.maxsize > 2 ** 32
-  win_binary_dir = os.path.join(path.GetTelemetryDir(), 'bin', 'win')
-  dll_file_name = 'WinRing0x64.dll' if python_is_64_bit else 'WinRing0.dll'
-  dll_path = os.path.join(win_binary_dir, dll_file_name)
-
-  os_is_64_bit = 'PROGRAMFILES(X86)' in os.environ
-  executable_dir = os.path.dirname(sys.executable)
-  driver_file_name = 'WinRing0x64.sys' if os_is_64_bit else 'WinRing0.sys'
-  driver_path = os.path.join(executable_dir, driver_file_name)
-
-  # Check for WinRing0 and download if needed.
-  if not (os.path.exists(dll_path) and os.path.exists(driver_path)):
-    zip_path = os.path.join(win_binary_dir, 'winring0.zip')
-    cloud_storage.GetIfChanged(zip_path, bucket=cloud_storage.PUBLIC_BUCKET)
-    try:
-      with zipfile.ZipFile(zip_path, 'r') as zip_file:
-        # Install DLL.
-        if not os.path.exists(dll_path):
-          zip_file.extract(dll_file_name, win_binary_dir)
-        # Install kernel driver.
-        if not os.path.exists(driver_path):
-          zip_file.extract(driver_file_name, executable_dir)
-    finally:
-      os.remove(zip_path)
-
-  return dll_path
-
-
-def _Initialize():
-  global _winring0
-  if not _winring0:
-    winring0 = ctypes.WinDLL(WinRing0Path())
-    if not winring0.InitializeOls():
-      winring0_status = winring0.GetDllStatus()
-      raise WinRing0Error(winring0_status,
-                          'Unable to initialize WinRing0: %s' %
-                          WINRING0_STATUS_MESSAGES[winring0_status])
-    _winring0 = winring0
-    atexit.register(_Deinitialize)
-
-
-def _Deinitialize():
-  global _winring0
-  if _winring0:
-    _winring0.DeinitializeOls()
-    _winring0 = None
-
-
-def _ReadMsr(msr_number):
-  low = ctypes.c_uint()
-  high = ctypes.c_uint()
-  _winring0.Rdmsr(ctypes.c_uint(msr_number),
-                  ctypes.byref(low), ctypes.byref(high))
-  return high.value << 32 | low.value
-
-
-@decorators.Cache
-def _EnergyMultiplier():
-  return 0.5 ** ((_ReadMsr(MSR_RAPL_POWER_UNIT) >> 8) & 0x1f)
-
-
-def _PackageEnergyJoules():
-  return _ReadMsr(MSR_PKG_ENERGY_STATUS) * _EnergyMultiplier()
-
-
-def _TemperatureCelsius():
-  tcc_activation_temp = _ReadMsr(IA32_TEMPERATURE_TARGET) >> 16 & 0x7f
-  if tcc_activation_temp <= 0:
-    tcc_activation_temp = 105
-  package_temp_headroom = _ReadMsr(IA32_PACKAGE_THERM_STATUS) >> 16 & 0x7f
-  return tcc_activation_temp - package_temp_headroom
-
-
 def _JoulesToMilliwattHours(value_joules):
   return value_joules * 1000 / 3600.
 
@@ -149,16 +48,15 @@ class MsrPowerMonitor(power_monitor.PowerMonitor):
       return False
 
     try:
-      _Initialize()
-    except OSError:
-      return False
-
-    if _PackageEnergyJoules() <= 0:
-      logging.info('Cannot monitor power: no energy readings.')
-      return False
-
-    if _TemperatureCelsius() <= 0:
-      logging.info('Cannot monitor power: no temperature readings.')
+      if self._PackageEnergyJoules() <= 0:
+        logging.info('Cannot monitor power: no energy readings.')
+        return False
+
+      if self._TemperatureCelsius() <= 0:
+        logging.info('Cannot monitor power: no temperature readings.')
+        return False
+    except OSError as e:
+      logging.info('Cannot monitor power: %s' % e)
       return False
 
     return True
@@ -166,16 +64,15 @@ class MsrPowerMonitor(power_monitor.PowerMonitor):
   def StartMonitoringPower(self, browser):
     assert self._start_energy_j is None and self._start_temp_c is None, (
         'Called StartMonitoringPower() twice.')
-    _Initialize()
-    self._start_energy_j = _PackageEnergyJoules()
-    self._start_temp_c = _TemperatureCelsius()
+    self._start_energy_j = self._PackageEnergyJoules()
+    self._start_temp_c = self._TemperatureCelsius()
 
   def StopMonitoringPower(self):
     assert not(self._start_energy_j is None or self._start_temp_c is None), (
         'Called StopMonitoringPower() before StartMonitoringPower().')
 
-    energy_consumption_j = _PackageEnergyJoules() - self._start_energy_j
-    average_temp_c = (_TemperatureCelsius() + self._start_temp_c) / 2.
+    energy_consumption_j = self._PackageEnergyJoules() - self._start_energy_j
+    average_temp_c = (self._TemperatureCelsius() + self._start_temp_c) / 2.
     assert energy_consumption_j >= 0, ('Negative energy consumption. (Starting '
                                        'energy was %s.)' % self._start_energy_j)
 
@@ -191,3 +88,20 @@ class MsrPowerMonitor(power_monitor.PowerMonitor):
             },
         },
     }
+
+  @decorators.Cache
+  def _EnergyMultiplier(self):
+    return 0.5 ** ((self._backend.ReadMsr(MSR_RAPL_POWER_UNIT) >> 8) & 0x1f)
+
+  def _PackageEnergyJoules(self):
+    return (self._backend.ReadMsr(MSR_PKG_ENERGY_STATUS) *
+            self._EnergyMultiplier())
+
+  def _TemperatureCelsius(self):
+    tcc_activation_temp = (
+        self._backend.ReadMsr(IA32_TEMPERATURE_TARGET) >> 16 & 0x7f)
+    if tcc_activation_temp <= 0:
+      tcc_activation_temp = 105
+    package_temp_headroom = (
+        self._backend.ReadMsr(IA32_PACKAGE_THERM_STATUS) >> 16 & 0x7f)
+    return tcc_activation_temp - package_temp_headroom