Re: [Qemu-devel] [PATCH 0/5] Add some tracepoints for clarification of the cause of troubles

[Kazuya Saito]

(2013/03/26 16:15), Paolo Bonzini wrote:
> Il 26/03/2013 08:13, Kazuya Saito ha scritto:
>>>>
>>>> I'm not sure 4-5 are that useful, but the first 3 patches are definitely
>>>> good stuff.
>> Thanks. I'll modify the patch you pointed out about CPU number and
>> re-post it.
>> I'd like to add tracepoints to the virtual device creation/deletion
>> part.  I had an issue that when a Windows guest OS booted up, it didn't
>> have a virtual NIC device which it should have had.  It took us time to
>> figure out which the guest OS or the QEMU had the issue.  If I have
>> had the tracepoints in the virtual device creation/deletion should have
>> eased the situation much better.
> 
> Wouldn't you get the same information from the command line?

I think the information you said is different from what I meant. The
information I wanted to know is whether QEMU creates/deletes a device
successfully or not. We cannot get it from the command line.
I was sure I specified a NIC device for the guest, but the Windows guest
didn't have it when it booted.  There were two possibilities.  One was
QEMU failed to create the NIC device, and the other was QEMU created it
successfully and the Windows guest failed to detect it.  Since QEMU
output limited message at the moment, it was difficult to prove that
it was not QEMU's issue.  I took a coredump of the QEMU and proved the
QEMU must have a valid structures for the NIC device.  I believe the
tracepoints could have allowed me to figure out where the issue existed
a lot faster and easier.  (And it turned out it was the Windows' issue.)

Kazuya