Re: [RFC PATCH 2/2] cxl: Add tprintk support for header log hex dump

[Dave Jiang <dave.jiang@intel.com>]

On 1/18/23 2:43 AM, Jonathan Cameron wrote:
> On Tue, 17 Jan 2023 11:08:26 -0700
> Dave Jiang <dave.jiang@intel.com> wrote:
> 
>> On 1/13/23 8:40 AM, Jonathan Cameron wrote:
>>> May not make sense in general, but very helpful when writing multiple
>>> header logging support.
>>>
>>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>
>> The user logging software would be retrieving from the log data directly
>> instead of parsing the trace output right? Will people visually inspect
>> the formatted trace output? Useful for debugging?
> 
> Rather depends on the use case and rate of expected errors + if you are
> trying to debug errors before your logging infrastructure is up.
> 
> Sure in production, likely these tracepoints would just get stored to a DB for later
> querying.  But in debug, I often just use the kernel parameter
> to directly dump them in the main kernel log, or perf's own decoding of a trace.
> 
> The nearest equivalent to this is AER which does print the log.
> https://elixir.bootlin.com/linux/v6.2-rc4/source/include/ras/ras_event.h#L337
> 
> though that uses __print_array so maybe that's a better choice.
> Don't get the nice offsets though if we do that though...
> 
> I'm not fussed about this patch going upstream or not, it just makes testing
> patch 1 a lot easier :)

Thanks for the explanation.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> 
> Jonathan
> 
> 
>>
>>> ---
>>>    drivers/cxl/core/trace.h | 7 +++++--
>>>    1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h
>>> index 20ca2fe2ca8e..64f6ad13529d 100644
>>> --- a/drivers/cxl/core/trace.h
>>> +++ b/drivers/cxl/core/trace.h
>>> @@ -62,10 +62,13 @@ TRACE_EVENT(cxl_aer_uncorrectable_error,
>>>    		 */
>>>    		memcpy(__entry->header_log, hl, CXL_HEADERLOG_SIZE);
>>>    	),
>>> -	TP_printk("%s: status: '%s' first_error: '%s'",
>>> +	TP_printk("%s: status: '%s' first_error: '%s' header_log: %s",
>>>    		  __get_str(dev_name),
>>>    		  show_uc_errs(__entry->status),
>>> -		  show_uc_errs(__entry->first_error)
>>> +		  show_uc_errs(__entry->first_error),
>>> +		__print_hex_dump("", DUMP_PREFIX_OFFSET, 32, 4,
>>> +				(char *)__entry->header_log,
>>> +				CXL_HEADERLOG_SIZE_U32, false)
>>>    	)
>>>    );
>>>      
>