[Qemu-devel] [PATCH][RESEND] qemu/kvm_stat: Fix I/O error from kvm_stat

[Hemant Kumar <hemant@linux.vnet.ibm.com>]

Running kvm_stat on a powerpc macine where the kernel is compiled with
KVM_BOOK3S_HV_EXIT_TIMING config option, generates the following error :

 # kvm_stat

Traceback (most recent call last):
  File "/usr/bin/kvm_stat", line 644, in <module>
    curses.wrapper(tui, stats)
  File "/usr/lib64/python2.7/curses/wrapper.py", line 43, in wrapper
    return func(stdscr, *args, **kwds)
  File "/usr/bin/kvm_stat", line 550, in tui
    refresh(sleeptime)
  File "/usr/bin/kvm_stat", line 526, in refresh
    s = stats.get()
  File "/usr/bin/kvm_stat", line 486, in get
    new = d.read()
  File "/usr/bin/kvm_stat", line 29, in read
    return dict([(key, val(key)) for key in self._fields])
  File "/usr/bin/kvm_stat", line 28, in val
    return int(file(self.base + '/' + key).read())
IOError: [Errno 21] Is a directory: '/sys/kernel/debug/kvm/vm12840'

The error says that its trying to read the contents of a directory as if
it were a file. The kernel here creates directories inside
"/sys/kernel/debug/kvm/" for the individual VMs running on the
machine. These directories contain timing information (for rm_entry,
rm_intr, rm_exit, guest, cede) related to each vcpu of each VM. All of
this is enabled with KVM_BOOK3S_HV_EXIT_TIMING config option for the
kernel.

kvm_stat script isn't supposed to parse/read these directories and isn't
even expecting any directories inside "/sys/kernel/debug/kvm/". This
patch fixes the problem by avoiding lookup for these directories.

Reported-by: Krishnaja Balachandran <kribalac@in.ibm.com>
Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
---
 scripts/kvm/kvm_stat | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/kvm/kvm_stat b/scripts/kvm/kvm_stat
index 7e5d256..1da7a53 100755
--- a/scripts/kvm/kvm_stat
+++ b/scripts/kvm/kvm_stat
@@ -18,7 +18,11 @@ from ctypes import *
 class DebugfsProvider(object):
     def __init__(self):
         self.base = '/sys/kernel/debug/kvm'
-        self._fields = os.listdir(self.base)
+        files = os.listdir(self.base)
+        self._fields = []
+        for f in files:
+            if os.path.isfile(self.base + '/' + f):
+                self._fields.append(f)
     def fields(self):
         return self._fields
     def select(self, fields):
-- 
1.9.3