On 31/08/12 18:20, Daniel P. Berrange wrote:
On Fri, Aug 31, 2012 at 08:09:46AM -0700, Daniel P. Berrange wrote:
On Fri, Aug 31, 2012 at 03:23:18PM +0300, NoxDaFox wrote:
Here's the typical output:
File "/home/nox/workspace/NOX/src/NOX/hooks.py", line 134, in trigger
hook.trigger(event)
File "/home/nox/workspace/NOX/src/NOX/hooks.py", line 33, in trigger
self.handlers[event]()
File "/home/nox/workspace/NOX/hooks/volatility.py", line 81, in memory_dump
for block in Memory(self.ctx):
File "/home/see/workspace/NOX/src/NOX/lib/libtools.py", line 179, in next
libvirt.VIR_MEMORY_PHYSICAL)
File "/usr/lib/python2.7/dist-packages/libvirt.py", line 1759, in memoryPeek
ret = libvirtmod.virDomainMemoryPeek(self._o, start, size, flags)
SystemError: error return without exception set
Hmm, that's a peculiar message to see - I can't find anywhere in the
libvirt code that uses that particular messages, so I'm not sure what
has gone wrong here.
Oh, I think this might be a python message. Our C binding does
LIBVIRT_BEGIN_ALLOW_THREADS;
c_retval = virDomainMemoryPeek(domain, start, size, buf, flags);
LIBVIRT_END_ALLOW_THREADS;
if (c_retval< 0)
goto cleanup;
py_retval = PyString_FromStringAndSize(buf, size);
cleanup:
VIR_FREE(buf);
return py_retval;
}
In the 'c_retval< 0' check, I think we should have been doing
if (c_retval< 0) {
py_retval = VIR_PY_NONE;
goto cleanup;
}
so we actually return Python's idea of None, rather than C's NULL,
at which point you'd probably see the real error message from
libvirt/QEMU
Daniel
I looked more deeply into the code and I agree with you about the reason
of that weird behavior when the error shows.
What I don't get is why the error should show.
I made more tests on different platforms and the behavior seems more
random than expected.
What I'm doing is iterate over the memory, repeatedly calling the
memoryPeek() command on memory blocks of 64Kb as libvirt's RPC driver is
limited to this size.
Everything happens from separate processes peeking memory of separate
virtual machines in suspended state during all the process; this means
that whatever is happening on the guests is not running at the moment,
neither the guest itself.
Do you know which version of QEMU is supporting the dump-guest-memory?
NoxDaFox
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