Commit 874b1cfa authored by Wei Huang's avatar Wei Huang Committed by Paolo Bonzini
Browse files

kvm_stat: Print errno when syscall to perf_event_open() fails 



kvm_stat uses syscall() to call perf_event_open(). If this function
call fails, the returned value is -1, which doesn't tell the details
of such failure (i.e. ENOSYS or EINVAL). This patch retrieves errno
and prints it when syscall() fails. The error message will look like
"Exception: perf_event_open failed, errno = 38".

Signed-off-by: default avatarWei Huang <wei@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2c9d535a

scripts/kvm/kvm_stat

+6 −1
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 


import curses

import sys, os, time, optparse, ctypes

from ctypes import *



class DebugfsProvider(object):

    def __init__(self):
@@ -247,6 +248,9 @@ import struct, array 


libc = ctypes.CDLL('libc.so.6')

syscall = libc.syscall

get_errno = libc.__errno_location

get_errno.restype = POINTER(c_int)



class perf_event_attr(ctypes.Structure):

    _fields_ = [('type', ctypes.c_uint32),

                ('size', ctypes.c_uint32),
@@ -330,7 +334,8 @@ class Event(object): 
            group_leader = group.events[0].fd

        fd = _perf_event_open(attr, -1, group.cpu, group_leader, 0)

        if fd == -1:

            raise Exception('perf_event_open failed')

            err = get_errno()[0]

            raise Exception('perf_event_open failed, errno = ' + err.__str__())

        if filter:

            import fcntl

            fcntl.ioctl(fd, ioctl_numbers['SET_FILTER'], filter)