Re: [Qemu-block] Enable debugging in a running vServer

[Paolo Bonzini]

On 26/03/2015 15:54, Peter Lieven wrote:
> Hi Block people,
> 
> we recently observed some strange I/O stalls on some vServers. I suspect
> a bug in the target and
> already added some debugging output to libiscsi that could have helped
> to track the issue.
> 
> However, to enable this debugging I would need to call
> 
> iscsi_set_log_level
> 
> during runtime from the hmp or qmp.
> 
> I wonder what would be the best way to do this and/or if it would be
> interesting to have a generic
> way to tell a block backend to enter debugging whereas I would leave it
> up to the backend driver
> what exactly that means?
> 
> Other option would be to set an enviroment variable during runtime. But
> as far as I know thats
> not possible.

Depending on the kind of logging that you want, the best thing to do
would be to add tracepoint support (similar to QEMU's tracetool, perhaps
using it) to libiscsi.  But I understand that it would be a large work.

Paolo