build/android/install_emulator_deps.py: run kvm-ok as root when needed.

build/android/install_emulator_deps.py

 #!/usr/bin/env python
 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Installs deps for using SDK emulator for testing.
 
 The script will download the SDK and system images, if they are not present, and
 install and enable KVM, if virtualization has been enabled in the BIOS.
 """
@@ skipping 82 matching lines @@
                                      api_target, 'x86'))
 
 
 def CheckKVM():
   """Check if KVM is enabled.
 
   Returns:
     True if kvm-ok returns 0 (already enabled)
   """
   try:
+    # Note: Running kvm-ok as root is recommended, but not required, to get
+    #       better information in case of failure. I.e.:
+    #
+    #       If root:
+    #          - If /dev/kvm is available, returns 0 (success)
+    #
+    #          - Otherwise, print information explaining whether the CPU
+    #            supports KVM extensions, and whether they're disabled by the
+    #            BIOS, then return 1 (failure).
+    #
+    #       If _not_ root:
+    #          - If /dev/kvm is available, returns 0 (success)
+    #
+    #          - Otherwise, print a message asking to run it as root, and
+    #            return 1 (failure).
+    #
+    # Here, there is no need to run it as root, but it is done in InstallKVM()
+    # below.
     return not cmd_helper.RunCmd(['kvm-ok'])
   except OSError:
     logging.info('kvm-ok not installed')
     return False
 
 
 def GetSDK():
   """Download the SDK and unzip it into EMULATOR_SDK_ROOT."""
   logging.info('Download Android SDK.')
   sdk_url = '%s/%s' % (SDK_BASE_URL, SDK_ZIP)
@@ skipping 18 matching lines @@
   if rc:
     logging.critical('ERROR: Did not install KVM. Make sure hardware '
                      'virtualization is enabled in BIOS (i.e. Intel VT-x or '
                      'AMD SVM).')
   # TODO(navabi): Use modprobe kvm-amd on AMD processors.
   rc = cmd_helper.RunCmd(['sudo', 'modprobe', 'kvm-intel'])
   if rc:
     logging.critical('ERROR: Did not add KVM module to Linux Kernal. Make sure '
                      'hardware virtualization is enabled in BIOS.')
   # Now check to ensure KVM acceleration can be used.
-  rc = cmd_helper.RunCmd(['kvm-ok'])
+  # Run as root to get better diagnostics in case of failure (see note in
+  # CheckKVM() above).
+  rc = cmd_helper.RunCmd(['sudo', 'kvm-ok'])

[navabi, 2013/12/16 19:43:08]

Should we just call CheckKVM() here rather than doing "sudo kvm-ok", and then in
CheckKVM() use sudo to get better failure information?

[digit1, 2013/12/17 08:41:43]

Actually, it looks like all /usr/sbin binaries should require root, and aren't
necessarily in a regular user's $PATH. This means we should always call it with
'sudo', I've updated the patch.

This also means that install_emulator_deps.py will always ask for the sudo
password, even if there is nothing to install, if we want to avoid this, we
better just check for /dev/kvm in CheckKVM() instead, which can be done without
root privileges. What do you think?

[navabi, 2013/12/17 21:31:04]

I like that idea.

   if rc:
     logging.critical('ERROR: Can not use KVM acceleration. Make sure hardware '
                      'virtualization is enabled in BIOS (i.e. Intel VT-x or '
                      'AMD SVM).')
 
 
 def GetX86Image(api_level=DEFAULT_ANDROID_API_LEVEL):
   """Download x86 system image from Intel's website.
 
   Args:
@@ skipping 101 matching lines @@
 
   # Make sure KVM packages are installed and enabled.
   if CheckKVM():
     logging.info('KVM already installed and enabled.')
   else:
     InstallKVM()
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))