Re: [Qemu-devel] QMP: RFC: I/O error info & query-stop-reason

[Daniel P. Berrange]

On Mon, Jun 06, 2011 at 08:08:51AM -0500, Anthony Liguori wrote:
> On 06/06/2011 04:25 AM, Kevin Wolf wrote:
> >Am 02.06.2011 20:09, schrieb Luiz Capitulino:
> >>>>I'm ok with either way. But in case you meant the second one, I guess
> >>>>we should make "reason" a dictionary so that we can group related
> >>>>information when we extend the field, for example:
> >>>>
> >>>>   "reason": { "no space": false, "no permission": true }
> >
> >Splitting up enums into a number of booleans looks like a bad idea to
> >me. It makes things more verbose than they should be, and even worse, it
> >implies that more than one field could be true.
> 
> I agree.  What I had suggested was to not have a reason at all.
> 
> >
> >If this new schema thing doesn't support proper enums, that's something
> >that should be changed.
> 
> It does BTW.
> 
> >>>
> >>>Why would we ever have "no permission"?
> >>
> >>It's an I/O error. I have a report from a developer who was getting
> >>the BLOCK_IO_ERROR event and had to debug qemu to know the error cause,
> >>it turned out to be no permission.
> >
> >And I want to add that it's a PITA to handle bug report when the only
> >message you get from qemu is "something went wrong". Sorry, that's not
> >useful at all. I want to see the real error reason (and at least for
> >debugging this means, I want to see the errno value/string).
> >
> >Finding out that it was -EACCES in fact cost me (and QA who ran into the
> >problem) much more time than it should have. It's simply too much that
> >you need to attach gdb to find out what really happened.
> 
> You want a log file and you want libvirt to actually let QEMU write
> to a log file.

Anything QEMU writes to stderr or stdout gets recorded in a
per-VM logfile already at /var/log/libvirt/qemu/$GUESTNAME.log

Regards,
Daniel
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