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 from typing import List, Optional
  21
  22
  23 LOG = logging.getLogger(__name__)
  24
  25 # Mapping host architecture to any additional architectures it can
  26 # support which often includes its 32 bit cousin.
  27 ADDITIONAL_ARCHES = {
  28     "x86_64": "i386",
  29     "aarch64": "armhf",
  30     "ppc64le": "ppc64",
  31 }
  32
  33
  34 def list_accel(qemu_bin: str) -> List[str]:
  35     """
  36     List accelerators enabled in the QEMU binary.
  37
  38     @param qemu_bin (str): path to the QEMU binary.
  39     @raise Exception: if failed to run `qemu -accel help`
  40     @return a list of accelerator names.
  41     """
  42     if not qemu_bin:
  43         return []
  44     try:
  45         out = subprocess.check_output([qemu_bin, '-accel', 'help'],
  46                                       universal_newlines=True)
  47     except:
  48         LOG.debug("Failed to get the list of accelerators in %s", qemu_bin)
  49         raise
  50     # Skip the first line which is the header.
  51     return [acc.strip() for acc in out.splitlines()[1:]]
  52
  53
  54 def kvm_available(target_arch: Optional[str] = None,
  55                   qemu_bin: Optional[str] = None) -> bool:
  56     """
  57     Check if KVM is available using the following heuristic:
  58       - Kernel module is present in the host;
  59       - Target and host arches don't mismatch;
  60       - KVM is enabled in the QEMU binary.
  61
  62     @param target_arch (str): target architecture
  63     @param qemu_bin (str): path to the QEMU binary
  64     @return True if kvm is available, otherwise False.
  65     """
  66     if not os.access("/dev/kvm", os.R_OK | os.W_OK):
  67         return False
  68     if target_arch:
  69         host_arch = os.uname()[4]
  70         if target_arch != host_arch:
  71             if target_arch != ADDITIONAL_ARCHES.get(host_arch):
  72                 return False
  73     if qemu_bin and "kvm" not in list_accel(qemu_bin):
  74         return False
  75     return True
  76
  77
  78 def tcg_available(qemu_bin: str) -> bool:
  79     """
  80     Check if TCG is available.
  81
  82     @param qemu_bin (str): path to the QEMU binary
  83     """
  84     return 'tcg' in list_accel(qemu_bin)