kvm_stat

#!/usr/bin/python
#
# top-like utility for displaying kvm statistics
#
# Copyright 2006-2008 Qumranet Technologies
# Copyright 2008-2011 Red Hat, Inc.
#
# Authors:
#  Avi Kivity <avi@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2.  See
# the COPYING file in the top-level directory.
"""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.
"""

import curses
import sys
import os
import time
import optparse
import ctypes
import fcntl
import resource
import struct
import re
import subprocess
from collections import defaultdict

VMX_EXIT_REASONS = {
    'EXCEPTION_NMI':        0,
    'EXTERNAL_INTERRUPT':   1,
    'TRIPLE_FAULT':         2,
    'PENDING_INTERRUPT':    7,
    'NMI_WINDOW':           8,
    'TASK_SWITCH':          9,
    'CPUID':                10,
    'HLT':                  12,
    '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,
    'MWAIT_INSTRUCTION':    36,
    'MONITOR_INSTRUCTION':  39,
    'PAUSE_INSTRUCTION':    40,
    'MCE_DURING_VMENTRY':   41,
    'TPR_BELOW_THRESHOLD':  43,
    'APIC_ACCESS':          44,
    'EPT_VIOLATION':        48,
    'EPT_MISCONFIG':        49,
    'WBINVD':               54,
    'XSETBV':               55,
    'APIC_WRITE':           56,
    'INVPCID':              58,
}

SVM_EXIT_REASONS = {
    'READ_CR0':       0x000,
    'READ_CR3':       0x003,
    'READ_CR4':       0x004,
    'READ_CR8':       0x008,
    'WRITE_CR0':      0x010,
    '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,
    '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,
    'NPF':            0x400,
}

# EC definition of HSR (from arch/arm64/include/asm/kvm_arm.h)
AARCH64_EXIT_REASONS = {
    'UNKNOWN':      0x00,
    'WFI':          0x01,
    'CP15_32':      0x03,
    'CP15_64':      0x04,
    'CP14_MR':      0x05,
    'CP14_LS':      0x06,
    'FP_ASIMD':     0x07,
    'CP10_ID':      0x08,
    'CP14_64':      0x0C,
    'ILL_ISS':      0x0E,
    'SVC32':        0x11,
    'HVC32':        0x12,
    'SMC32':        0x13,
    'SVC64':        0x15,
    'HVC64':        0x16,
    'SMC64':        0x17,
    'SYS64':        0x18,
    'IABT':         0x20,
    'IABT_HYP':     0x21,
    'PC_ALIGN':     0x22,
    'DABT':         0x24,
    'DABT_HYP':     0x25,
    'SP_ALIGN':     0x26,
    'FP_EXC32':     0x28,
    'FP_EXC64':     0x2C,
    'SERROR':       0x2F,
    'BREAKPT':      0x30,
    'BREAKPT_HYP':  0x31,
    'SOFTSTP':      0x32,
    'SOFTSTP_HYP':  0x33,
    'WATCHPT':      0x34,
    'WATCHPT_HYP':  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,
}

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


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


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


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_reasons = {}


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


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

ARCH = Arch.get_arch()


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))


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


def get_pid_from_gname(gname):
    """Fuzzy function to convert guest name to QEMU process pid.

    Returns a list of potential pids, can be empty if no match found.
    Throws an exception on processing errors.

    """
    pids = []
    try:
        child = subprocess.Popen(['ps', '-A', '--format', 'pid,args'],
                                 stdout=subprocess.PIPE)
    except:
        raise Exception
    for line in child.stdout:
        line = line.lstrip().split(' ', 1)
        # perform a sanity check before calling the more expensive
        # function to possibly extract the guest name
        if ' -name ' in line[1] and gname == get_gname_from_pid(line[0]):
            pids.append(int(line[0]))
    child.stdout.close()

    return pids


def get_gname_from_pid(pid):
    """Returns the guest name for a QEMU process pid.

    Extracts the guest name from the QEMU comma line by processing the '-name'
    option. Will also handle names specified out of sequence.

    """
    name = ''
    try:
        line = open('/proc/{}/cmdline'.format(pid), 'rb').read().split('\0')
        parms = line[line.index('-name') + 1].split(',')
        while '' in parms:
            # commas are escaped (i.e. ',,'), hence e.g. 'foo,bar' results in
            # ['foo', '', 'bar'], which we revert here
            idx = parms.index('')
            parms[idx - 1] += ',' + parms[idx + 1]
            del parms[idx:idx+2]
        # the '-name' switch allows for two ways to specify the guest name,
        # where the plain name overrides the name specified via 'guest='
        for arg in parms:
            if '=' not in arg:
                name = arg
                break
            if arg[:6] == 'guest=':
                name = arg[6:]
    except (ValueError, IOError, IndexError):
        pass

    return name


def get_online_cpus():
    """Returns a list of cpu id integers."""
    with open('/sys/devices/system/cpu/online') as cpu_list:
        cpu_string = cpu_list.readline()
        return parse_int_list(cpu_string)


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_reasons:
        filters['kvm_exit'] = ('exit_reason', ARCH.exit_reasons)
    return filters

libc = ctypes.CDLL('libc.so.6', use_errno=True)
syscall = libc.syscall


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


def perf_event_open(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 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))

PERF_TYPE_TRACEPOINT = 2
PERF_FORMAT_GROUP = 1 << 3

PATH_DEBUGFS_TRACING = '/sys/kernel/debug/tracing'
PATH_DEBUGFS_KVM = '/sys/kernel/debug/kvm'


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

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

    """
    def __init__(self):
        self.group_leaders = []
        self.filters = get_filters()
        self._fields = self.get_available_fields()
        self._pid = 0

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

        All available events have directories under
        /sys/kernel/debug/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 = 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 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 = walkdir(path)[1]
        else:
            groupids = 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)

    def available_fields(self):
        return self.get_available_fields()

    @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):
        """Returns 'event name: current value' for all enabled events."""
        ret = defaultdict(int)
        for group in self.group_leaders:
            for name, val in group.read().iteritems():
                if name in self._fields:
                    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(object):
    """Provides data from the files that KVM creates in the kvm debugfs
    folder."""
    def __init__(self):
        self._fields = self.get_available_fields()
        self._baseline = {}
        self._pid = 0
        self.do_read = True
        self.paths = []
        self.reset()

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

        The fields are all available KVM debugfs files

        """
        return walkdir(PATH_DEBUGFS_KVM)[2]

    @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):
        if pid != 0:
            self._pid = pid

            vms = walkdir(PATH_DEBUGFS_KVM)[1]
            if len(vms) == 0:
                self.do_read = False

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

        else:
            self.paths = []
            self.do_read = True
        self.reset()

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

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

        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:
                    self._baseline[key] = value
                if self._baseline.get(key, -1) == -1:
                    self._baseline[key] = value
                results[field] = (results.get(field, 0) + value -
                                  self._baseline.get(key, 0))

        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)


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, providers, pid, fields=None):
        self.providers = providers
        self._pid_filter = pid
        self._fields_filter = fields
        self.values = {}
        self.update_provider_pid()
        self.update_provider_filters()

    def update_provider_filters(self):
        """Propagates fields filters to providers."""
        def wanted(key):
            if not self._fields_filter:
                return True
            return re.match(self._fields_filter, key) is not None

        # 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_fields = [key for key in provider.get_available_fields()
                               if wanted(key)]
            provider.fields = provider_fields

    def update_provider_pid(self):
        """Propagates pid filters to providers."""
        for provider in self.providers:
            provider.pid = self._pid_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 = {}
            self.update_provider_pid()

    def get(self):
        """Returns a dict with field -> (value, delta to last value) of all
        provider data."""
        for provider in self.providers:
            new = provider.read()
            for key in provider.fields:
                oldval = self.values.get(key, (0, 0))[0]
                newval = new.get(key, 0)
                newdelta = newval - oldval
                self.values[key] = (newval, newdelta)
        return self.values

LABEL_WIDTH = 40
NUMBER_WIDTH = 10
DELAY_INITIAL = 0.25
DELAY_REGULAR = 3.0
MAX_GUEST_NAME_LEN = 48
MAX_REGEX_LEN = 44
DEFAULT_REGEX = r'^[^\(]*$'


class Tui(object):
    """Instruments curses to draw a nice text ui."""
    def __init__(self, stats):
        self.stats = stats
        self.screen = None
        self.update_drilldown()

    def __enter__(self):
        """Initialises curses for later use.  Based on curses.wrapper
           implementation from the Python standard library."""
        self.screen = curses.initscr()
        curses.noecho()
        curses.cbreak()

        # The try/catch works around a minor bit of
        # over-conscientiousness in the curses module, the error
        # return from C start_color() is ignorable.
        try:
            curses.start_color()
        except curses.error:
            pass

        # Hide cursor in extra statement as some monochrome terminals
        # might support hiding but not colors.
        try:
            curses.curs_set(0)
        except curses.error:
            pass

        curses.use_default_colors()
        return self

    def __exit__(self, *exception):
        """Resets the terminal to its normal state.  Based on curses.wrappre
           implementation from the Python standard library."""
        if self.screen:
            self.screen.keypad(0)
            curses.echo()
            curses.nocbreak()
            curses.endwin()

    def update_drilldown(self):
        """Sets or removes a filter that only allows fields without braces."""
        if not self.stats.fields_filter:
            self.stats.fields_filter = DEFAULT_REGEX

        elif self.stats.fields_filter == DEFAULT_REGEX:
            self.stats.fields_filter = None

    def update_pid(self, pid):
        """Propagates pid selection to stats object."""
        self.stats.pid_filter = pid

    def refresh_header(self, pid=None):
        """Refreshes the header."""
        if pid is None:
            pid = self.stats.pid_filter
        self.screen.erase()
        gname = get_gname_from_pid(pid)
        if gname:
            gname = ('({})'.format(gname[:MAX_GUEST_NAME_LEN] + '...'
                                   if len(gname) > MAX_GUEST_NAME_LEN
                                   else gname))
        if pid > 0:
            self.screen.addstr(0, 0, 'kvm statistics - pid {0} {1}'
                               .format(pid, gname), curses.A_BOLD)
        else:
            self.screen.addstr(0, 0, 'kvm statistics - summary', curses.A_BOLD)
        if self.stats.fields_filter and self.stats.fields_filter \
           != DEFAULT_REGEX:
            regex = self.stats.fields_filter
            if len(regex) > MAX_REGEX_LEN:
                regex = regex[:MAX_REGEX_LEN] + '...'
            self.screen.addstr(1, 17, 'regex filter: {0}'.format(regex))
        self.screen.addstr(2, 1, 'Event')
        self.screen.addstr(2, 1 + LABEL_WIDTH + NUMBER_WIDTH -
                           len('Total'), 'Total')
        self.screen.addstr(2, 1 + LABEL_WIDTH + NUMBER_WIDTH + 7 -
                           len('%Total'), '%Total')
        self.screen.addstr(2, 1 + LABEL_WIDTH + NUMBER_WIDTH + 7 + 8 -
                           len('Current'), 'Current')
        self.screen.addstr(4, 1, 'Collecting data...')
        self.screen.refresh()

    def refresh_body(self, sleeptime):
        row = 3
        self.screen.move(row, 0)
        self.screen.clrtobot()
        stats = self.stats.get()

        def sortkey(x):
            if stats[x][1]:
                return (-stats[x][1], -stats[x][0])
            else:
                return (0, -stats[x][0])
        total = 0.
        for val in stats.values():
            total += val[0]
        for key in sorted(stats.keys(), key=sortkey):

            if row >= self.screen.getmaxyx()[0]:
                break
            values = stats[key]
            if not values[0] and not values[1]:
                break
            col = 1
            self.screen.addstr(row, col, key)
            col += LABEL_WIDTH
            self.screen.addstr(row, col, '%10d' % (values[0],))
            col += NUMBER_WIDTH
            self.screen.addstr(row, col, '%7.1f' % (values[0] * 100 / total,))
            col += 7
            if values[1] is not None:
                self.screen.addstr(row, col, '%8d' % (values[1] / sleeptime,))
            row += 1
        self.screen.refresh()

    def show_filter_selection(self):
        """Draws filter selection mask.

        Asks for a valid regex and sets the fields filter accordingly.

        """
        while True:
            self.screen.erase()
            self.screen.addstr(0, 0,
                               "Show statistics for events matching a regex.",
                               curses.A_BOLD)
            self.screen.addstr(2, 0,
                               "Current regex: {0}"
                               .format(self.stats.fields_filter))
            self.screen.addstr(3, 0, "New regex: ")
            curses.echo()
            regex = self.screen.getstr()
            curses.noecho()
            if len(regex) == 0:
                self.stats.fields_filter = DEFAULT_REGEX
                self.refresh_header()
                return
            try:
                re.compile(regex)
                self.stats.fields_filter = regex
                self.refresh_header()
                return
            except re.error:
                continue

    def show_vm_selection_by_pid(self):
        """Draws PID selection mask.

        Asks for a pid until a valid pid or 0 has been entered.

        """
        msg = ''
        while True:
            self.screen.erase()
            self.screen.addstr(0, 0,
                               'Show statistics for specific pid.',
                               curses.A_BOLD)
            self.screen.addstr(1, 0,
                               'This might limit the shown data to the trace '
                               'statistics.')
            self.screen.addstr(5, 0, msg)

            curses.echo()
            self.screen.addstr(3, 0, "Pid [0 or pid]: ")
            pid = self.screen.getstr()
            curses.noecho()

            try:
                if len(pid) > 0:
                    pid = int(pid)
                    if pid != 0 and not os.path.isdir(os.path.join('/proc/',
                                                                   str(pid))):
                        msg = '"' + str(pid) + '": Not a running process'
                        continue
                else:
                    pid = 0
                self.refresh_header(pid)
                self.update_pid(pid)
                break

            except ValueError:
                msg = '"' + str(pid) + '": Not a valid pid'
                continue

    def show_vm_selection_by_guest_name(self):
        """Draws guest selection mask.

        Asks for a guest name until a valid guest name or '' is entered.

        """
        msg = ''
        while True:
            self.screen.erase()
            self.screen.addstr(0, 0,
                               'Show statistics for specific guest.',
                               curses.A_BOLD)
            self.screen.addstr(1, 0,
                               'This might limit the shown data to the trace '
                               'statistics.')
            self.screen.addstr(5, 0, msg)
            curses.echo()
            self.screen.addstr(3, 0, "Guest [ENTER or guest]: ")
            gname = self.screen.getstr()
            curses.noecho()

            if not gname:
                self.refresh_header(0)
                self.update_pid(0)
                break
            else:
                pids = []
                try:
                    pids = get_pid_from_gname(gname)
                except:
                    msg = '"' + gname + '": Internal error while searching, ' \
                          'use pid filter instead'
                    continue
                if len(pids) == 0:
                    msg = '"' + gname + '": Not an active guest'
                    continue
                if len(pids) > 1:
                    msg = '"' + gname + '": Multiple matches found, use pid ' \
                          'filter instead'
                    continue
                self.refresh_header(pids[0])
                self.update_pid(pids[0])
                break

    def show_stats(self):
        """Refreshes the screen and processes user input."""
        sleeptime = DELAY_INITIAL
        self.refresh_header()
        while True:
            self.refresh_body(sleeptime)
            curses.halfdelay(int(sleeptime * 10))
            sleeptime = DELAY_REGULAR
            try:
                char = self.screen.getkey()
                if char == 'x':
                    self.refresh_header()
                    self.update_drilldown()
                    sleeptime = DELAY_INITIAL
                if char == 'q':
                    break
                if char == 'c':
                    self.stats.fields_filter = DEFAULT_REGEX
                    self.refresh_header(0)
                    self.update_pid(0)
                    sleeptime = DELAY_INITIAL
                if char == 'f':
                    self.show_filter_selection()
                    sleeptime = DELAY_INITIAL
                if char == 'g':
                    self.show_vm_selection_by_guest_name()
                    sleeptime = DELAY_INITIAL
                if char == 'p':
                    self.show_vm_selection_by_pid()
                    sleeptime = DELAY_INITIAL
                if char == 'r':
                    self.refresh_header()
                    self.stats.reset()
                    sleeptime = DELAY_INITIAL
            except KeyboardInterrupt:
                break
            except curses.error:
                continue


def batch(stats):
    """Prints statistics in a key, value format."""
    try:
        s = stats.get()
        time.sleep(1)
        s = stats.get()
        for key in sorted(s.keys()):
            values = s[key]
            print '%-42s%10d%10d' % (key, values[0], values[1])
    except KeyboardInterrupt:
        pass


def log(stats):
    """Prints statistics as reiterating key block, multiple value blocks."""
    keys = sorted(stats.get().iterkeys())

    def banner():
        for k in keys:
            print '%s' % k,
        print

    def statline():
        s = stats.get()
        for k in keys:
            print ' %9d' % s[k][1],
        print
    line = 0
    banner_repeat = 20
    while True:
        try:
            time.sleep(1)
            if line % banner_repeat == 0:
                banner()
            statline()
            line += 1
        except KeyboardInterrupt:
            break


def get_options():
    """Returns processed program arguments."""
    description_text = """
This script displays various statistics about VMs running under KVM.
The statistics are gathered from the KVM debugfs entries and / or the
currently available perf traces.

The monitoring takes additional cpu cycles and might affect the VM's
performance.

Requirements:
- Access to:
    /sys/kernel/debug/kvm
    /sys/kernel/debug/trace/events/*
    /proc/pid/task
- /proc/sys/kernel/perf_event_paranoid < 1 if user has no
  CAP_SYS_ADMIN and perf events are used.
- CAP_SYS_RESOURCE if the hard limit is not high enough to allow
  the large number of files that are possibly opened.

Interactive Commands:
   c     clear filter
   f     filter by regular expression
   g     filter by guest name
   p     filter by PID
   q     quit
   x     toggle reporting of stats for individual child trace events
   r     reset stats
Press any other key to refresh statistics immediately.
"""

    class PlainHelpFormatter(optparse.IndentedHelpFormatter):
        def format_description(self, description):
            if description:
                return description + "\n"
            else:
                return ""

    def cb_guest_to_pid(option, opt, val, parser):
        try:
            pids = get_pid_from_gname(val)
        except:
            raise optparse.OptionValueError('Error while searching for guest '
                                            '"{}", use "-p" to specify a pid '
                                            'instead'.format(val))
        if len(pids) == 0:
            raise optparse.OptionValueError('No guest by the name "{}" '
                                            'found'.format(val))
        if len(pids) > 1:
            raise optparse.OptionValueError('Multiple processes found (pids: '
                                            '{}) - use "-p" to specify a pid '
                                            'instead'.format(" ".join(pids)))
        parser.values.pid = pids[0]

    optparser = optparse.OptionParser(description=description_text,
                                      formatter=PlainHelpFormatter())
    optparser.add_option('-1', '--once', '--batch',
                         action='store_true',
                         default=False,
                         dest='once',
                         help='run in batch mode for one second',
                         )
    optparser.add_option('-l', '--log',
                         action='store_true',
                         default=False,
                         dest='log',
                         help='run in logging mode (like vmstat)',
                         )
    optparser.add_option('-t', '--tracepoints',
                         action='store_true',
                         default=False,
                         dest='tracepoints',
                         help='retrieve statistics from tracepoints',
                         )
    optparser.add_option('-d', '--debugfs',
                         action='store_true',
                         default=False,
                         dest='debugfs',
                         help='retrieve statistics from debugfs',
                         )
    optparser.add_option('-f', '--fields',
                         action='store',
                         default=None,
                         dest='fields',
                         help='fields to display (regex)',
                         )
    optparser.add_option('-p', '--pid',
                         action='store',
                         default=0,
                         type='int',
                         dest='pid',
                         help='restrict statistics to pid',
                         )
    optparser.add_option('-g', '--guest',
                         action='callback',
                         type='string',
                         dest='pid',
                         metavar='GUEST',
                         help='restrict statistics to guest by name',
                         callback=cb_guest_to_pid,
                         )
    (options, _) = optparser.parse_args(sys.argv)
    return options


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

    if options.tracepoints:
        providers.append(TracepointProvider())
    if options.debugfs:
        providers.append(DebugfsProvider())
    if len(providers) == 0:
        providers.append(TracepointProvider())

    return providers


def check_access(options):
    """Exits if the current user can't access all needed directories."""
    if not os.path.exists('/sys/kernel/debug'):
        sys.stderr.write('Please enable CONFIG_DEBUG_FS in your kernel.')
        sys.exit(1)

    if not os.path.exists(PATH_DEBUGFS_KVM):
        sys.stderr.write("Please make sure, that debugfs is mounted and "
                         "readable by the current user:\n"
                         "('mount -t debugfs debugfs /sys/kernel/debug')\n"
                         "Also ensure, that the kvm modules are loaded.\n")
        sys.exit(1)

    if not os.path.exists(PATH_DEBUGFS_TRACING) and (options.tracepoints or
                                                     not options.debugfs):
        sys.stderr.write("Please enable CONFIG_TRACING in your kernel "
                         "when using the option -t (default).\n"
                         "If it is enabled, make {0} readable by the "
                         "current user.\n"
                         .format(PATH_DEBUGFS_TRACING))
        if options.tracepoints:
            sys.exit(1)

        sys.stderr.write("Falling back to debugfs statistics!\n")
        options.debugfs = True
        time.sleep(5)

    return options


def main():
    options = get_options()
    options = check_access(options)

    if (options.pid > 0 and
        not os.path.isdir(os.path.join('/proc/',
                                       str(options.pid)))):
        sys.stderr.write('Did you use a (unsupported) tid instead of a pid?\n')
        sys.exit('Specified pid does not exist.')

    providers = get_providers(options)
    stats = Stats(providers, options.pid, fields=options.fields)

    if options.log:
        log(stats)
    elif not options.once:
        with Tui(stats) as tui:
            tui.show_stats()
    else:
        batch(stats)

if __name__ == "__main__":
    main()