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 LOG = logging.getLogger(__name__)
  22
  23 # Mapping host architecture to any additional architectures it can
  24 # support which often includes its 32 bit cousin.
  25 ADDITIONAL_ARCHES = {
  26     "x86_64" : "i386",
  27     "aarch64" : "armhf",
  28     "ppc64le" : "ppc64",
  29 }
  30
  31 def list_accel(qemu_bin):
  32     """
  33     List accelerators enabled in the QEMU binary.
  34
  35     @param qemu_bin (str): path to the QEMU binary.
  36     @raise Exception: if failed to run `qemu -accel help`
  37     @return a list of accelerator names.
  38     """
  39     if not qemu_bin:
  40         return []
  41     try:
  42         out = subprocess.check_output([qemu_bin, '-accel', 'help'],
  43                                       universal_newlines=True)
  44     except:
  45         LOG.debug("Failed to get the list of accelerators in %s", qemu_bin)
  46         raise
  47     # Skip the first line which is the header.
  48     return [acc.strip() for acc in out.splitlines()[1:]]
  49
  50 def kvm_available(target_arch=None, qemu_bin=None):
  51     """
  52     Check if KVM is available using the following heuristic:
  53       - Kernel module is present in the host;
  54       - Target and host arches don't mismatch;
  55       - KVM is enabled in the QEMU binary.
  56
  57     @param target_arch (str): target architecture
  58     @param qemu_bin (str): path to the QEMU binary
  59     @return True if kvm is available, otherwise False.
  60     """
  61     if not os.access("/dev/kvm", os.R_OK | os.W_OK):
  62         return False
  63     if target_arch:
  64         host_arch = os.uname()[4]
  65         if target_arch != host_arch:
  66             if target_arch != ADDITIONAL_ARCHES.get(host_arch):
  67                 return False
  68     if qemu_bin and "kvm" not in list_accel(qemu_bin):
  69         return False
  70     return True
  71
  72 def tcg_available(qemu_bin):
  73     """
  74     Check if TCG is available.
  75
  76     @param qemu_bin (str): path to the QEMU binary
  77     """
  78     return 'tcg' in list_accel(qemu_bin)