# Copyright 2020 Google, Inc.
#
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Import('*')

from gem5_scons import warning

import gem5_scons
host_isa = None
try:
    import platform
    host_isa = platform.machine()
except:
    pass

with gem5_scons.Configure(main) as conf:
    # Check if we should enable KVM-based hardware virtualization. The API
    # we rely on exists since version 2.6.36 of the kernel, but somehow
    # the KVM_API_VERSION does not reflect the change. We test for one of
    # the types as a fall back.
    conf.env['KVM_ISA'] = None
    if not conf.CheckHeader('linux/kvm.h', '<>'):
        print("Info: Compatible header file <linux/kvm.h> not found, "
              "disabling KVM support.")
    elif not conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ],
            'C', 'timer_create(CLOCK_MONOTONIC, NULL, NULL);'):
        warning("Cannot enable KVM, host doesn't support POSIX timers")
    elif host_isa == 'x86_64':
        if conf.CheckTypeSize('struct kvm_xsave',
                '#include <linux/kvm.h>') != 0:
            conf.env['KVM_ISA'] = 'x86'
        else:
            warning("KVM on x86 requires xsave support in kernel headers.")
    elif host_isa in ('armv7l', 'aarch64'):
        conf.env['KVM_ISA'] = 'arm'
    else:
        warning("Failed to determine host ISA.")

    if conf.env['KVM_ISA']:
        # Check if the exclude_host attribute is available. We want this to
        # get accurate instruction counts in KVM.
        conf.env['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
            'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')

        # Warn about missing optional functionality
        if not conf.env['HAVE_PERF_ATTR_EXCLUDE_HOST']:
            warning("perf_event headers lack support for the exclude_host "
                    "attribute. KVM instruction counts will be inaccurate.")

        export_vars.append('HAVE_PERF_ATTR_EXCLUDE_HOST')

if main['KVM_ISA']:
    sticky_vars.Add(BoolVariable('USE_KVM',
                'Enable hardware virtualized (KVM) CPU models', True))
else:
    main['USE_KVM'] = False
    warning("Can not enable KVM, host seems to lack KVM support")

export_vars.append('USE_KVM')