#! /usr/bin/python3 -sP
# SPDX-License-Identifier: GPL-2.0-only
#
# top-like utility for displaying kvm statistics
#
# Copyright 2006-2008 Qumranet Technologies
# Copyright 2008-2011 Red Hat, Inc.
#
# Authors:
#  Avi Kivity <avi@redhat.com>
#
"""The kvm_stat module outputs statistics about running KVM VMs

Three different ways of output formatting are available:
- as a top-like text ui
- in a key -> value format
- in an all keys, all values format

The data is sampled from the KVM's debugfs entries and its perf events.
"""
from __future__ import print_function

import curses
import sys
import locale
import os
import time
import argparse
import ctypes
import fcntl
import resource
import struct
import re
import subprocess
import signal
from collections import defaultdict, namedtuple
from functools import reduce
from datetime import datetime

VMX_EXIT_REASONS = {
    'EXCEPTION_NMI':        0,
    'EXTERNAL_INTERRUPT':   1,
    'TRIPLE_FAULT':         2,
    'INIT_SIGNAL':          3,
    'SIPI_SIGNAL':          4,
    'INTERRUPT_WINDOW':     7,
    'NMI_WINDOW':           8,
    'TASK_SWITCH':          9,
    'CPUID':                10,
    'HLT':                  12,
    'INVD':                 13,
    'INVLPG':               14,
    'RDPMC':                15,
    'RDTSC':                16,
    'VMCALL':               18,
    'VMCLEAR':              19,
    'VMLAUNCH':             20,
    'VMPTRLD':              21,
    'VMPTRST':              22,
    'VMREAD':               23,
    'VMRESUME':             24,
    'VMWRITE':              25,
    'VMOFF':                26,
    'VMON':                 27,
    'CR_ACCESS':            28,
    'DR_ACCESS':            29,
    'IO_INSTRUCTION':       30,
    'MSR_READ':             31,
    'MSR_WRITE':            32,
    'INVALID_STATE':        33,
    'MSR_LOAD_FAIL':        34,
    'MWAIT_INSTRUCTION':    36,
    'MONITOR_TRAP_FLAG':    37,
    'MONITOR_INSTRUCTION':  39,
    'PAUSE_INSTRUCTION':    40,
    'MCE_DURING_VMENTRY':   41,
    'TPR_BELOW_THRESHOLD':  43,
    'APIC_ACCESS':          44,
    'EOI_INDUCED':          45,
    'GDTR_IDTR':            46,
    'LDTR_TR':              47,
    'EPT_VIOLATION':        48,
    'EPT_MISCONFIG':        49,
    'INVEPT':               50,
    'RDTSCP':               51,
    'PREEMPTION_TIMER':     52,
    'INVVPID':              53,
    'WBINVD':               54,
    'XSETBV':               55,
    'APIC_WRITE':           56,
    'RDRAND':               57,
    'INVPCID':              58,
    'VMFUNC':               59,
    'ENCLS':                60,
    'RDSEED':               61,
    'PML_FULL':             62,
    'XSAVES':               63,
    'XRSTORS':              64,
    'UMWAIT':               67,
    'TPAUSE':               68,
    'BUS_LOCK':             74,
    'NOTIFY':               75,
}

SVM_EXIT_REASONS = {
    'READ_CR0':       0x000,
    'READ_CR2':       0x002,
    'READ_CR3':       0x003,
    'READ_CR4':       0x004,
    'READ_CR8':       0x008,
    'WRITE_CR0':      0x010,
    'WRITE_CR2':      0x012,
    'WRITE_CR3':      0x013,
    'WRITE_CR4':      0x014,
    'WRITE_CR8':      0x018,
    'READ_DR0':       0x020,
    'READ_DR1':       0x021,
    'READ_DR2':       0x022,
    'READ_DR3':       0x023,
    'READ_DR4':       0x024,
    'READ_DR5':       0x025,
    'READ_DR6':       0x026,
    'READ_DR7':       0x027,
    'WRITE_DR0':      0x030,
    'WRITE_DR1':      0x031,
    'WRITE_DR2':      0x032,
    'WRITE_DR3':      0x033,
    'WRITE_DR4':      0x034,
    'WRITE_DR5':      0x035,
    'WRITE_DR6':      0x036,
    'WRITE_DR7':      0x037,
    'EXCP_BASE':      0x040,
    'LAST_EXCP':      0x05f,
    'INTR':           0x060,
    'NMI':            0x061,
    'SMI':            0x062,
    'INIT':           0x063,
    'VINTR':          0x064,
    'CR0_SEL_WRITE':  0x065,
    'IDTR_READ':      0x066,
    'GDTR_READ':      0x067,
    'LDTR_READ':      0x068,
    'TR_READ':        0x069,
    'IDTR_WRITE':     0x06a,
    'GDTR_WRITE':     0x06b,
    'LDTR_WRITE':     0x06c,
    'TR_WRITE':       0x06d,
    'RDTSC':          0x06e,
    'RDPMC':          0x06f,
    'PUSHF':          0x070,
    'POPF':           0x071,
    'CPUID':          0x072,
    'RSM':            0x073,
    'IRET':           0x074,
    'SWINT':          0x075,
    'INVD':           0x076,
    'PAUSE':          0x077,
    'HLT':            0x078,
    'INVLPG':         0x079,
    'INVLPGA':        0x07a,
    'IOIO':           0x07b,
    'MSR':            0x07c,
    'TASK_SWITCH':    0x07d,
    'FERR_FREEZE':    0x07e,
    'SHUTDOWN':       0x07f,
    'VMRUN':          0x080,
    'VMMCALL':        0x081,
    'VMLOAD':         0x082,
    'VMSAVE':         0x083,
    'STGI':           0x084,
    'CLGI':           0x085,
    'SKINIT':         0x086,
    'RDTSCP':         0x087,
    'ICEBP':          0x088,
    'WBINVD':         0x089,
    'MONITOR':        0x08a,
    'MWAIT':          0x08b,
    'MWAIT_COND':     0x08c,
    'XSETBV':         0x08d,
    'RDPRU':          0x08e,
    'EFER_WRITE_TRAP':           0x08f,
    'CR0_WRITE_TRAP':            0x090,
    'CR1_WRITE_TRAP':            0x091,
    'CR2_WRITE_TRAP':            0x092,
    'CR3_WRITE_TRAP':            0x093,
    'CR4_WRITE_TRAP':            0x094,
    'CR5_WRITE_TRAP':            0x095,
    'CR6_WRITE_TRAP':            0x096,
    'CR7_WRITE_TRAP':            0x097,
    'CR8_WRITE_TRAP':            0x098,
    'CR9_WRITE_TRAP':            0x099,
    'CR10_WRITE_TRAP':           0x09a,
    'CR11_WRITE_TRAP':           0x09b,
    'CR12_WRITE_TRAP':           0x09c,
    'CR13_WRITE_TRAP':           0x09d,
    'CR14_WRITE_TRAP':           0x09e,
    'CR15_WRITE_TRAP':           0x09f,
    'INVPCID':        0x0a2,
    'NPF':            0x400,
    'AVIC_INCOMPLETE_IPI':       0x401,
    'AVIC_UNACCELERATED_ACCESS': 0x402,
    'VMGEXIT':        0x403,
}

# EC definition of HSR (from arch/arm64/include/asm/esr.h)
AARCH64_EXIT_REASONS = {
    'UNKNOWN':      0x00,
    'WFx':          0x01,
    'CP15_32':      0x03,
    'CP15_64':      0x04,
    'CP14_MR':      0x05,
    'CP14_LS':      0x06,
    'FP_ASIMD':     0x07,
    'CP10_ID':      0x08,
    'PAC':          0x09,
    'CP14_64':      0x0C,
    'BTI':          0x0D,
    'ILL':          0x0E,
    'SVC32':        0x11,
    'HVC32':        0x12,
    'SMC32':        0x13,
    'SVC64':        0x15,
    'HVC64':        0x16,
    'SMC64':        0x17,
    'SYS64':        0x18,
    'SVE':          0x19,
    'ERET':         0x1A,
    'FPAC':         0x1C,
    'SME':          0x1D,
    'IMP_DEF':      0x1F,
    'IABT_LOW':     0x20,
    'IABT_CUR':     0x21,
    'PC_ALIGN':     0x22,
    'DABT_LOW':     0x24,
    'DABT_CUR':     0x25,
    'SP_ALIGN':     0x26,
    'FP_EXC32':     0x28,
    'FP_EXC64':     0x2C,
    'SERROR':       0x2F,
    'BREAKPT_LOW':  0x30,
    'BREAKPT_CUR':  0x31,
    'SOFTSTP_LOW':  0x32,
    'SOFTSTP_CUR':  0x33,
    'WATCHPT_LOW':  0x34,
    'WATCHPT_CUR':  0x35,
    'BKPT32':       0x38,
    'VECTOR32':     0x3A,
    'BRK64':        0x3C,
}

# From include/uapi/linux/kvm.h, KVM_EXIT_xxx
USERSPACE_EXIT_REASONS = {
    'UNKNOWN':          0,
    'EXCEPTION':        1,
    'IO':               2,
    'HYPERCALL':        3,
    'DEBUG':            4,
    'HLT':              5,
    'MMIO':             6,
    'IRQ_WINDOW_OPEN':  7,
    'SHUTDOWN':         8,
    'FAIL_ENTRY':       9,
    'INTR':             10,
    'SET_TPR':          11,
    'TPR_ACCESS':       12,
    'S390_SIEIC':       13,
    'S390_RESET':       14,
    'DCR':              15,
    'NMI':              16,
    'INTERNAL_ERROR':   17,
    'OSI':              18,
    'PAPR_HCALL':       19,
    'S390_UCONTROL':    20,
    'WATCHDOG':         21,
    'S390_TSCH':        22,
    'EPR':              23,
    'SYSTEM_EVENT':     24,
    'S390_STSI':        25,
    'IOAPIC_EOI':       26,
    'HYPERV':           27,
    'ARM_NISV':         28,
    'X86_RDMSR':        29,
    'X86_WRMSR':        30,
    'DIRTY_RING_FULL':  31,
    'AP_RESET_HOLD':    32,
    'X86_BUS_LOCK':     33,
    'XEN':              34,
    'RISCV_SBI':        35,
    'RISCV_CSR':        36,
    'NOTIFY':           37,
}

IOCTL_NUMBERS = {
    'SET_FILTER':  0x40082406,
    'ENABLE':      0x00002400,
    'DISABLE':     0x00002401,
    'RESET':       0x00002403,
}

signal_received = False

ENCODING = locale.getpreferredencoding(False)
TRACE_FILTER = re.compile(r'^[^\(]*$')


class Arch(object):
    """Encapsulates global architecture specific data.

    Contains the performance event open syscall and ioctl numbers, as
    well as the VM exit reasons for the architecture it runs on.

    """
    @staticmethod
    def get_arch():
        machine = os.uname()[4]

        if machine.startswith('ppc'):
            return ArchPPC()
        elif machine.startswith('aarch64'):
            return ArchA64()
        elif machine.startswith('s390'):
            return ArchS390()
        else:
            # X86_64
            for line in open('/proc/cpuinfo'):
                if not line.startswith('flags'):
                    continue

                flags = line.split()
                if 'vmx' in flags:
                    return ArchX86(VMX_EXIT_REASONS)
                if 'svm' in flags:
                    return ArchX86(SVM_EXIT_REASONS)
                return

    def tracepoint_is_child(self, field):
        if (TRACE_FILTER.match(field)):
            return None
        return field.split('(', 1)[0]


class ArchX86(Arch):
    def __init__(self, exit_reasons):
        self.sc_perf_evt_open = 298
        self.ioctl_numbers = IOCTL_NUMBERS
        self.exit_reason_field = 'exit_reason'
        self.exit_reasons = exit_reasons

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        return None


class ArchPPC(Arch):
    def __init__(self):
        self.sc_perf_evt_open = 319
        self.ioctl_numbers = IOCTL_NUMBERS
        self.ioctl_numbers['ENABLE'] = 0x20002400
        self.ioctl_numbers['DISABLE'] = 0x20002401
        self.ioctl_numbers['RESET'] = 0x20002403

        # PPC comes in 32 and 64 bit and some generated ioctl
        # numbers depend on the wordsize.
        char_ptr_size = ctypes.sizeof(ctypes.c_char_p)
        self.ioctl_numbers['SET_FILTER'] = 0x80002406 | char_ptr_size << 16
        self.exit_reason_field = 'exit_nr'
        self.exit_reasons = {}

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        return None


class ArchA64(Arch):
    def __init__(self):
        self.sc_perf_evt_open = 241
        self.ioctl_numbers = IOCTL_NUMBERS
        self.exit_reason_field = 'esr_ec'
        self.exit_reasons = AARCH64_EXIT_REASONS

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        return None


class ArchS390(Arch):
    def __init__(self):
        self.sc_perf_evt_open = 331
        self.ioctl_numbers = IOCTL_NUMBERS
        self.exit_reason_field = None
        self.exit_reasons = None

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        if field.startswith('instruction_'):
            return 'exit_instruction'


ARCH = Arch.get_arch()


class perf_event_attr(ctypes.Structure):
    """Struct that holds the necessary data to set up a trace event.

    For an extensive explanation see perf_event_open(2) and
    include/uapi/linux/perf_event.h, struct perf_event_attr

    All fields that are not initialized in the constructor are 0.

    """
    _fields_ = [('type', ctypes.c_uint32),
                ('size', ctypes.c_uint32),
                ('config', ctypes.c_uint64),
                ('sample_freq', ctypes.c_uint64),
                ('sample_type', ctypes.c_uint64),
                ('read_format', ctypes.c_uint64),
                ('flags', ctypes.c_uint64),
                ('wakeup_events', ctypes.c_uint32),
                ('bp_type', ctypes.c_uint32),
                ('bp_addr', ctypes.c_uint64),
                ('bp_len', ctypes.c_uint64),
                ]

    def __init__(self):
        super(self.__class__, self).__init__()
        self.type = PERF_TYPE_TRACEPOINT
        self.size = ctypes.sizeof(self)
        self.read_format = PERF_FORMAT_GROUP


PERF_TYPE_TRACEPOINT = 2
PERF_FORMAT_GROUP = 1 << 3


class Group(object):
    """Represents a perf event group."""

    def __init__(self):
        self.events = []

    def add_event(self, event):
        self.events.append(event)

    def read(self):
        """Returns a dict with 'event name: value' for all events in the
        group.

        Values are read by reading from the file descriptor of the
        event that is the group leader. See perf_event_open(2) for
        details.

        Read format for the used event configuration is:
        struct read_format {
            u64 nr; /* The number of events */
            struct {
                u64 value; /* The value of the event */
            } values[nr];
        };

        """
        length = 8 * (1 + len(self.events))
        read_format = 'xxxxxxxx' + 'Q' * len(self.events)
        return dict(zip([event.name for event in self.events],
                        struct.unpack(read_format,
                                      os.read(self.events[0].fd, length))))


class Event(object):
    """Represents a performance event and manages its life cycle."""
    def __init__(self, name, group, trace_cpu, trace_pid, trace_point,
                 trace_filter, trace_set='kvm'):
        self.libc = ctypes.CDLL('libc.so.6', use_errno=True)
        self.syscall = self.libc.syscall
        self.name = name
        self.fd = None
        self._setup_event(group, trace_cpu, trace_pid, trace_point,
                          trace_filter, trace_set)

    def __del__(self):
        """Closes the event's file descriptor.

        As no python file object was created for the file descriptor,
        python will not reference count the descriptor and will not
        close it itself automatically, so we do it.

        """
        if self.fd:
            os.close(self.fd)

    def _perf_event_open(self, attr, pid, cpu, group_fd, flags):
        """Wrapper for the sys_perf_evt_open() syscall.

        Used to set up performance events, returns a file descriptor or -1
        on error.

        Attributes are:
        - syscall number
        - struct perf_event_attr *
        - pid or -1 to monitor all pids
        - cpu number or -1 to monitor all cpus
        - The file descriptor of the group leader or -1 to create a group.
        - flags

        """
        return self.syscall(ARCH.sc_perf_evt_open, ctypes.pointer(attr),
                            ctypes.c_int(pid), ctypes.c_int(cpu),
                            ctypes.c_int(group_fd), ctypes.c_long(flags))

    def _setup_event_attribute(self, trace_set, trace_point):
        """Returns an initialized ctype perf_event_attr struct."""

        id_path = os.path.join(PATH_DEBUGFS_TRACING, 'events', trace_set,
                               trace_point, 'id')

        event_attr = perf_event_attr()
        event_attr.config = int(open(id_path).read())
        return event_attr

    def _setup_event(self, group, trace_cpu, trace_pid, trace_point,
                     trace_filter, trace_set):
        """Sets up the perf event in Linux.

        Issues the syscall to register the event in the kernel and
        then sets the optional filter.

        """

        event_attr = self._setup_event_attribute(trace_set, trace_point)

        # First event will be group leader.
        group_leader = -1

        # All others have to pass the leader's descriptor instead.
        if group.events:
            group_leader = group.events[0].fd

        fd = self._perf_event_open(event_attr, trace_pid,
                                   trace_cpu, group_leader, 0)
        if fd == -1:
            err = ctypes.get_errno()
            raise OSError(err, os.strerror(err),
                          'while calling sys_perf_event_open().')

        if trace_filter:
            fcntl.ioctl(fd, ARCH.ioctl_numbers['SET_FILTER'],
                        trace_filter)

        self.fd = fd

    def enable(self):
        """Enables the trace event in the kernel.

        Enabling the group leader makes reading counters from it and the
        events under it possible.

        """
        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['ENABLE'], 0)

    def disable(self):
        """Disables the trace event in the kernel.

        Disabling the group leader makes reading all counters under it
        impossible.

        """
        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['DISABLE'], 0)

    def reset(self):
        """Resets the count of the trace event in the kernel."""
        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['RESET'], 0)


class Provider(object):
    """Encapsulates functionalities used by all providers."""
    def __init__(self, pid):
        self.child_events = False
        self.pid = pid

    @staticmethod
    def is_field_wanted(fields_filter, field):
        """Indicate whether field is valid according to fields_filter."""
        if not fields_filter:
            return True
        return re.match(fields_filter, field) is not None

    @staticmethod
    def walkdir(path):
        """Returns os.walk() data for specified directory.

        As it is only a wrapper it returns the same 3-tuple of (dirpath,
        dirnames, filenames).
        """
        return next(os.walk(path))


class TracepointProvider(Provider):
    """Data provider for the stats class.

    Manages the events/groups from which it acquires its data.

    """
    def __init__(self, pid, fields_filter):
        self.group_leaders = []
        self.filters = self._get_filters()
        self.update_fields(fields_filter)
        super(TracepointProvider, self).__init__(pid)

    @staticmethod
    def _get_filters():
        """Returns a dict of trace events, their filter ids and
        the values that can be filtered.

        Trace events can be filtered for special values by setting a
        filter string via an ioctl. The string normally has the format
        identifier==value. For each filter a new event will be created, to
        be able to distinguish the events.

        """
        filters = {}
        filters['kvm_userspace_exit'] = ('reason', USERSPACE_EXIT_REASONS)
        if ARCH.exit_reason_field and ARCH.exit_reasons:
            filters['kvm_exit'] = (ARCH.exit_reason_field, ARCH.exit_reasons)
        return filters

    def _get_available_fields(self):
        """Returns a list of available events of format 'event name(filter
        name)'.

        All available events have directories under
        /sys/kernel/tracing/events/ which export information
        about the specific event. Therefore, listing the dirs gives us
        a list of all available events.

        Some events like the vm exit reasons can be filtered for
        specific values. To take account for that, the routine below
        creates special fields with the following format:
        event name(filter name)

        """
        path = os.path.join(PATH_DEBUGFS_TRACING, 'events', 'kvm')
        fields = self.walkdir(path)[1]
        extra = []
        for field in fields:
            if field in self.filters:
                filter_name_, filter_dicts = self.filters[field]
                for name in filter_dicts:
                    extra.append(field + '(' + name + ')')
        fields += extra
        return fields

    def update_fields(self, fields_filter):
        """Refresh fields, applying fields_filter"""
        self.fields = [field for field in self._get_available_fields()
                       if self.is_field_wanted(fields_filter, field)]
        # add parents for child fields - otherwise we won't see any output!
        for field in self._fields:
            parent = ARCH.tracepoint_is_child(field)
            if (parent and parent not in self._fields):
                self.fields.append(parent)

    @staticmethod
    def _get_online_cpus():
        """Returns a list of cpu id integers."""
        def parse_int_list(list_string):
            """Returns an int list from a string of comma separated integers and
            integer ranges."""
            integers = []
            members = list_string.split(',')

            for member in members:
                if '-' not in member:
                    integers.append(int(member))
                else:
                    int_range = member.split('-')
                    integers.extend(range(int(int_range[0]),
                                          int(int_range[1]) + 1))

            return integers

        with open('/sys/devices/system/cpu/online') as cpu_list:
            cpu_string = cpu_list.readline()
            return parse_int_list(cpu_string)

    def _setup_traces(self):
        """Creates all event and group objects needed to be able to retrieve
        data."""
        fields = self._get_available_fields()
        if self._pid > 0:
            # Fetch list of all threads of the monitored pid, as qemu
            # starts a thread for each vcpu.
            path = os.path.join('/proc', str(self._pid), 'task')
            groupids = self.walkdir(path)[1]
        else:
            groupids = self._get_online_cpus()

        # The constant is needed as a buffer for python libs, std
        # streams and other files that the script opens.
        newlim = len(groupids) * len(fields) + 50
        try:
            softlim_, hardlim = resource.getrlimit(resource.RLIMIT_NOFILE)

            if hardlim < newlim:
                # Now we need CAP_SYS_RESOURCE, to increase the hard limit.
                resource.setrlimit(resource.RLIMIT_NOFILE, (newlim, newlim))
            else:
                # Raising the soft limit is sufficient.
                resource.setrlimit(resource.RLIMIT_NOFILE, (newlim, hardlim))

        except ValueError:
            sys.exit("NOFILE rlimit could not be raised to {0}".format(newlim))

        for groupid in groupids:
            group = Group()
            for name in fields:
                tracepoint = name
                tracefilter = None
                match = re.match(r'(.*)\((.*)\)', name)
                if match:
                    tracepoint, sub = match.groups()
                    tracefilter = ('%s==%d\0' %
                                   (self.filters[tracepoint][0],
                                    self.filters[tracepoint][1][sub]))

                # From perf_event_open(2):
                # pid > 0 and cpu == -1
                # This measures the specified process/thread on any CPU.
                #
                # pid == -1 and cpu >= 0
                # This measures all processes/threads on the specified CPU.
                trace_cpu = groupid if self._pid == 0 else -1
                trace_pid = int(groupid) if self._pid != 0 else -1

                group.add_event(Event(name=name,
                                      group=group,
                                      trace_cpu=trace_cpu,
                                      trace_pid=trace_pid,
                                      trace_point=tracepoint,
                                      trace_filter=tracefilter))

            self.group_leaders.append(group)

    @property
    def fields(self):
        return self._fields

    @fields.setter
    def fields(self, fields):
        """Enables/disables the (un)wanted events"""
        self._fields = fields
        for group in self.group_leaders:
            for index, event in enumerate(group.events):
                if event.name in fields:
                    event.reset()
                    event.enable()
                else:
                    # Do not disable the group leader.
                    # It would disable all of its events.
                    if index != 0:
                        event.disable()

    @property
    def pid(self):
        return self._pid

    @pid.setter
    def pid(self, pid):
        """Changes the monitored pid by setting new traces."""
        self._pid = pid
        # The garbage collector will get rid of all Event/Group
        # objects and open files after removing the references.
        self.group_leaders = []
        self._setup_traces()
        self.fields = self._fields

    def read(self, by_guest=0):
        """Returns 'event name: current value' for all enabled events."""
        ret = defaultdict(int)
        for group in self.group_leaders:
            for name, val in group.read().items():
                if name not in self._fields:
                    continue
                parent = ARCH.tracepoint_is_child(name)
                if parent:
                    name += ' ' + parent
                ret[name] += val
        return ret

    def reset(self):
        """Reset all field counters"""
        for group in self.group_leaders:
            for event in group.events:
                event.reset()


class DebugfsProvider(Provider):
    """Provides data from the files that KVM creates in the kvm debugfs
    folder."""
    def __init__(self, pid, fields_filter, include_past):
        self.update_fields(fields_filter)
        self._baseline = {}
        self.do_read = True
        self.paths = []
        super(DebugfsProvider, self).__init__(pid)
        if include_past:
            self._restore()

    def _get_available_fields(self):
        """"Returns a list of available fields.

        The fields are all available KVM debugfs files

        """
        exempt_list = ['halt_poll_fail_ns', 'halt_poll_success_ns', 'halt_wait_ns']
        fields = [field for field in self.walkdir(PATH_DEBUGFS_KVM)[2]
                  if field not in exempt_list]

        return fields

    def update_fields(self, fields_filter):
        """Refresh fields, applying fields_filter"""
        self._fields = [field for field in self._get_available_fields()
                        if self.is_field_wanted(fields_filter, field)]
        # add parents for child fields - otherwise we won't see any output!
        for field in self._fields:
            parent = ARCH.debugfs_is_child(field)
            if (parent and parent not in self._fields):
                self.fields.append(parent)

    @property
    def fields(self):
        return self._fields

    @fields.setter
    def fields(self, fields):
        self._fields = fields
        self.reset()

    @property
    def pid(self):
        return self._pid

    @pid.setter
    def pid(self, pid):
        self._pid = pid
        if pid != 0:
            vms = self.walkdir(PATH_DEBUGFS_KVM)[1]
            if len(vms) == 0:
                self.do_read = False

            self.paths = list(filter(lambda x: "{}-".format(pid) in x, vms))

        else:
            self.paths = []
            self.do_read = True

    def _verify_paths(self):
        """Remove invalid paths"""
        for path in self.paths:
            if not os.path.exists(os.path.join(PATH_DEBUGFS_KVM, path)):
                self.paths.remove(path)
                continue

    def read(self, reset=0, by_guest=0):
        """Returns a dict with format:'file name / field -> current value'.

        Parameter 'reset':
          0   plain read
          1   reset field counts to 0
          2   restore the original field counts

        """
        results = {}

        # If no debugfs filtering support is available, then don't read.
        if not self.do_read:
            return results
        self._verify_paths()

        paths = self.paths
        if self._pid == 0:
            paths = []
            for entry in os.walk(PATH_DEBUGFS_KVM):
                for dir in entry[1]:
                    paths.append(dir)
        for path in paths:
            for field in self._fields:
                value = self._read_field(field, path)
                key = path + field
                if reset == 1:
                    self._baseline[key] = value
                if reset == 2:
                    self._baseline[key] = 0
                if self._baseline.get(key, -1) == -1:
                    self._baseline[key] = value
                parent = ARCH.debugfs_is_child(field)
                if parent:
                    field = field + ' ' + parent
                else:
                    if by_guest:
                        field = key.split('-')[0]    # set 'field' to 'pid'
                increment = value - self._baseline.get(key, 0)
                if field in results:
                    results[field] += increment
                else:
                    results[field] = increment

        return results

    def _read_field(self, field, path):
        """Returns the value of a single field from a specific VM."""
        try:
            return int(open(os.path.join(PATH_DEBUGFS_KVM,
                                         path,
                                         field))
                       .read())
        except IOError:
            return 0

    def reset(self):
        """Reset field counters"""
        self._baseline = {}
        self.read(1)

    def _restore(self):
        """Reset field counters"""
        self._baseline = {}
        self.read(2)


EventStat = namedtuple('EventStat', ['value', 'delta'])


class Stats(object):
    """Manages the data providers and the data they provide.

    It is used to set filters on the provider's data and collect all
    provider data.

    """
    def __init__(self, options):
        self.providers = self._get_providers(options)
        self._pid_filter = options.pid
        self._fields_filter = options.fields
        self.values = {}
        self._child_events = False

    def _get_providers(self, options):
        """Returns a list of data providers depending on the passed options."""
        providers = []

        if options.debugfs:
            providers.append(DebugfsProvider(options.pid, options.fields,
                                             options.debugfs_include_past))
        if options.tracepoints or not providers:
            providers.append(TracepointProvider(options.pid, options.fields))

        return providers

    def _update_provider_filters(self):
        """Propagates fields filters to providers."""
        # As we reset the counters when updating the fields we can
        # also clear the cache of old values.
        self.values = {}
        for provider in self.providers:
            provider.update_fields(self._fields_filter)

    def reset(self):
        self.values = {}
        for provider in self.providers:
            provider.reset()

    @property
    def fields_filter(self):
        return self._fields_filter

    @fields_filter.setter
    def fields_filter(self, fields_filter):
        if fields_filter != self._fields_filter:
            self._fields_filter = fields_filter
            self._update_provider_filters()

    @property
    def pid_filter(self):
        return self._pid_filter

    @pid_filter.setter
    def pid_filter(self, pid):
        if pid != self._pid_filter:
            self._pid_filter = pid
            self.values = {}
            for provider in self.providers:
                provider.pid = self._pid_filter

    @property
    def child_events(self):
        return self._child_events

    @child_events.setter
    def child_events(self, val):
        self._child_events = val
        for provider in self.providers:
            provider.child_events = val

    def get(self, by_guest=0):
        """Returns a dict with field -> (value, delta to last value) of all
        provider data.
        Key formats:
          * plain: 'key' is event name
          * child-parent: 'key' is in format '<child> <parent>'
          * pid: 'key' is the pid of the guest, and the record contains the
               aggregated event data
        These formats are generated by the providers, and handled in class TUI.
        """
        for provider in self.providers:
            new = provider.read(by_guest=by_guest)
            for key in new:
                oldval = self.values.get(key, EventStat(0, 0)).value
                newval = new.get(key, 0)
                newdelta = newval - oldval
                self.values[key] = EventStat(newval, newdelta)
        return self.values

    def toggle_display_guests(self, to_pid):
        """Toggle between collection of stats by individual event and by
        guest pid

        Events reported by DebugfsProvider change when switching to/from
        reading by guest values. Hence we have to remove the excess event
        names from self.values.

        """
        if any(isinstance(ins, TracepointProvider) for ins in self.providers):
            return 1
        if to_pid:
            for provider in self.providers:
                if isinstance(provider, DebugfsProvider):
        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