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mwait.py
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55 lines (50 loc) · 2.34 KB
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# Copyright (c) 2015, Intel Corporation
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
# * Neither the name of Intel Corporation nor the names of its contributors
# may be used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
# ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""bits.mwait module."""
from __future__ import print_function
import bits
import contextlib
default_hint = 0x20
def quirk_default_hint(hint):
"""Set the default mwait hint"""
global default_hint
print("QUIRK: Setting default mwait hint from {:#x} to {:#x}".format(default_hint, hint))
default_hint = hint
@contextlib.contextmanager
def use_hint(hint=None):
"""Context manager to temporarily set the mwait hint of all CPUs"""
global default_hint
if hint is None:
hint = default_hint
old_mwait = {}
try:
for apicid in bits.cpus():
old_mwait[apicid] = bits.get_mwait(apicid)
bits.set_mwait(apicid, True, hint)
yield
finally:
for apicid, old_mwait_values in old_mwait.iteritems():
bits.set_mwait(apicid, *old_mwait_values)