[PATCH v3 2/5] python/qemu: accel: Add list_accel() method

[Wainer dos Santos Moschetta <wainersm@redhat.com>]

Since commit cbe6d6365a48 the command `qemu -accel help` returns
the list of accelerators enabled in the QEMU binary. This adds
the list_accel() method which return that same list.

Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 python/qemu/accel.py | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/python/qemu/accel.py b/python/qemu/accel.py
index cbeac10dd1..ddcdbfd9ae 100644
--- a/python/qemu/accel.py
+++ b/python/qemu/accel.py
@@ -14,7 +14,11 @@ accelerators.
 # the COPYING file in the top-level directory.
 #
 
+import logging
 import os
+import subprocess
+
+LOG = logging.getLogger(__name__)
 
 # Mapping host architecture to any additional architectures it can
 # support which often includes its 32 bit cousin.
@@ -23,6 +27,25 @@ ADDITIONAL_ARCHES = {
     "aarch64" : "armhf"
 }
 
+def list_accel(qemu_bin):
+    """
+    List accelerators enabled in the QEMU binary.
+
+    @param qemu_bin (str): path to the QEMU binary.
+    @raise Exception: if failed to run `qemu -accel help`
+    @return a list of accelerator names.
+    """
+    if not qemu_bin:
+        return []
+    try:
+        out = subprocess.check_output([qemu_bin, '-accel', 'help'],
+                                      universal_newlines=True)
+    except:
+        LOG.debug("Failed to get the list of accelerators in %s" % qemu_bin)
+        raise
+    # Skip the first line which is the header.
+    return [acc.strip() for acc in out.splitlines()[1:]]
+
 def kvm_available(target_arch=None):
     host_arch = os.uname()[4]
     if target_arch and target_arch != host_arch:
-- 
2.21.0