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

from gem5_scons import warning

import gem5_scons

# ISA code can set this to indicate what ISA KVM can target.
main['CONF'].setdefault('KVM_ISA', '')

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.

    main['CONF']['HAVE_KVM'] = False

    if not conf.CheckHeader('linux/kvm.h', '<>'):
        warning("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")
    else:
        # Generic support is available. We'll let the ISAs figure out if
        # it's really supported.
        conf.env['CONF']['HAVE_KVM'] = True

        # Check if the exclude_host attribute is available. We want this to
        # get accurate instruction counts in KVM.
        conf.env['CONF']['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['CONF']['HAVE_PERF_ATTR_EXCLUDE_HOST']:
            warning("perf_event headers lack support for the exclude_host "
                    "attribute. KVM instruction counts will be inaccurate.")

if not main['CONF']['KVM_ISA']:
    warning("Can not enable KVM, host seems to lack KVM support")