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

build/android/install_emulator_deps.py

Index: build/android/install_emulator_deps.py
diff --git a/build/android/install_emulator_deps.py b/build/android/install_emulator_deps.py
index ec923dfc8a99b26e36d1ea4326b2a58565e7e086..31242659a1ee5cad1879e2ff4cec72531e6694eb 100755
--- a/build/android/install_emulator_deps.py
+++ b/build/android/install_emulator_deps.py
@@ -100,6 +100,24 @@ def CheckKVM():
     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')
@@ -138,7 +156,9 @@ def InstallKVM():
     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 '