Re: [RFC PATCH 1/4] vfio-ccw: Refactor how the traces are built

[Eric Farman <farman@linux.ibm.com>]

On 10/15/19 9:46 AM, Cornelia Huck wrote:
> On Mon, 14 Oct 2019 20:08:52 +0200
> Eric Farman <farman@linux.ibm.com> wrote:
> 
>> Commit 3cd90214b70f ("vfio: ccw: add tracepoints for interesting error
>> paths") added a quick trace point to determine where a channel program
>> failed while being processed.  It's a great addition, but adding more
>> traces to vfio-ccw is more cumbersome than it needs to be.
>>
>> Let's refactor how this is done, so that additional traces are easier
>> to add and can exist outside of the FSM if we ever desire.
>>
>> Signed-off-by: Eric Farman <farman@linux.ibm.com>
>> ---
>>  drivers/s390/cio/Makefile         |  4 ++--
>>  drivers/s390/cio/vfio_ccw_cp.h    |  1 +
>>  drivers/s390/cio/vfio_ccw_fsm.c   |  3 ---
>>  drivers/s390/cio/vfio_ccw_trace.c | 12 ++++++++++++
>>  drivers/s390/cio/vfio_ccw_trace.h |  2 ++
>>  5 files changed, 17 insertions(+), 5 deletions(-)
>>  create mode 100644 drivers/s390/cio/vfio_ccw_trace.c
> 
> Looks good.
> 
> I'm wondering whether we could consolidate tracepoints and s390dbf
> usage somehow. These two complement each other in a way (looking at a
> live system vs. looking at a crash dump, integration with other parts
> of the system), but they currently also cover at least partially
> different code paths. Not sure how much sense it makes to have double
> coverage at least for a subset of the functionality.
> 

Yeah, there's gaps that could/should be closed, and maybe this patch
makes it easier to add traces to paths that s390dbf currently cover and
could benefit from having both.  Some more consideration of what is
covered and where, and what is missing, is certainliy needed.

 - Eric