python/qemu/accel.py

   1 """
   2 QEMU accel module:
   3
   4 This module provides utilities for discover and check the availability of
   5 accelerators.
   6 """
   7 # Copyright (C) 2015-2016 Red Hat Inc.
   8 # Copyright (C) 2012 IBM Corp.
   9 #
  10 # Authors:
  11 #  Fam Zheng <famz@redhat.com>
  12 #
  13 # This work is licensed under the terms of the GNU GPL, version 2.  See
  14 # the COPYING file in the top-level directory.
  15 #
  16
  17 import logging
  18 import os
  19 import subprocess
  20
  21
  22 LOG = logging.getLogger(__name__)
  23
  24 # Mapping host architecture to any additional architectures it can
  25 # support which often includes its 32 bit cousin.
  26 ADDITIONAL_ARCHES = {
  27     "x86_64": "i386",
  28     "aarch64": "armhf",
  29     "ppc64le": "ppc64",
  30 }
  31
  32
  33 def list_accel(qemu_bin):
  34     """
  35     List accelerators enabled in the QEMU binary.
  36
  37     @param qemu_bin (str): path to the QEMU binary.
  38     @raise Exception: if failed to run `qemu -accel help`
  39     @return a list of accelerator names.
  40     """
  41     if not qemu_bin:
  42         return []
  43     try:
  44         out = subprocess.check_output([qemu_bin, '-accel', 'help'],
  45                                       universal_newlines=True)
  46     except:
  47         LOG.debug("Failed to get the list of accelerators in %s", qemu_bin)
  48         raise
  49     # Skip the first line which is the header.
  50     return [acc.strip() for acc in out.splitlines()[1:]]
  51
  52
  53 def kvm_available(target_arch=None, qemu_bin=None):
  54     """
  55     Check if KVM is available using the following heuristic:
  56       - Kernel module is present in the host;
  57       - Target and host arches don't mismatch;
  58       - KVM is enabled in the QEMU binary.
  59
  60     @param target_arch (str): target architecture
  61     @param qemu_bin (str): path to the QEMU binary
  62     @return True if kvm is available, otherwise False.
  63     """
  64     if not os.access("/dev/kvm", os.R_OK | os.W_OK):
  65         return False
  66     if target_arch:
  67         host_arch = os.uname()[4]
  68         if target_arch != host_arch:
  69             if target_arch != ADDITIONAL_ARCHES.get(host_arch):
  70                 return False
  71     if qemu_bin and "kvm" not in list_accel(qemu_bin):
  72         return False
  73     return True
  74
  75
  76 def tcg_available(qemu_bin):
  77     """
  78     Check if TCG is available.
  79
  80     @param qemu_bin (str): path to the QEMU binary
  81     """
  82     return 'tcg' in list_accel(qemu_bin)