Re: [kvm-unit-tests PATCH v1 1/6] s390x: lib: css: disabling a subchannel

[Pierre Morel <pmorel@linux.ibm.com>]

On 3/19/21 10:02 AM, Janosch Frank wrote:
> On 3/18/21 2:26 PM, Pierre Morel wrote:
>> Some tests require to disable a subchannel.
>> Let's implement the css_disable() function.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> 
> Looks ok, minor nits below.
> 
>> ---
>>   lib/s390x/css.h     |  1 +
>>   lib/s390x/css_lib.c | 69 +++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 70 insertions(+)
>>
>> diff --git a/lib/s390x/css.h b/lib/s390x/css.h
>> index 7e3d261..b0de3a3 100644
>> --- a/lib/s390x/css.h
>> +++ b/lib/s390x/css.h
>> @@ -284,6 +284,7 @@ int css_enumerate(void);
>>   #define IO_SCH_ISC      3
>>   int css_enable(int schid, int isc);
>>   bool css_enabled(int schid);
>> +int css_disable(int schid);
>>   
>>   /* Library functions */
>>   int start_ccw1_chain(unsigned int sid, struct ccw1 *ccw);
>> diff --git a/lib/s390x/css_lib.c b/lib/s390x/css_lib.c
>> index efc7057..f8db205 100644
>> --- a/lib/s390x/css_lib.c
>> +++ b/lib/s390x/css_lib.c
>> @@ -186,6 +186,75 @@ bool css_enabled(int schid)
>>   	}
>>   	return true;
>>   }
>> +
>> +/*
>> + * css_disable: disable the subchannel
>> + * @schid: Subchannel Identifier
>> + * Return value:
>> + *   On success: 0
>> + *   On error the CC of the faulty instruction
>> + *      or -1 if the retry count is exceeded.
>> + */
>> +int css_disable(int schid)
>> +{
>> +	struct pmcw *pmcw = &schib.pmcw;
>> +	int retry_count = 0;
>> +	int cc;
>> +
>> +	/* Read the SCHIB for this subchannel */
>> +	cc = stsch(schid, &schib);
>> +	if (cc) {
>> +		report_info("stsch: sch %08x failed with cc=%d", schid, cc);
>> +		return cc;
>> +	}
>> +
>> +	if (!(pmcw->flags & PMCW_ENABLE)) {
>> +		report_info("stsch: sch %08x already disabled", schid);
>> +		return 0;
>> +	}
>> +
>> +retry:
>> +	/* Update the SCHIB to disable the subchannel */
>> +	pmcw->flags &= ~PMCW_ENABLE;
>> +
>> +	/* Tell the CSS we want to modify the subchannel */
>> +	cc = msch(schid, &schib);
>> +	if (cc) {
>> +		/*
>> +		 * If the subchannel is status pending or
>> +		 * if a function is in progress,
>> +		 * we consider both cases as errors.
>> +		 */
> 
> Weird indentation, the lines should be longer, no?
> 
>> +		report_info("msch: sch %08x failed with cc=%d", schid, cc);
>> +		return cc;
>> +	}
>> +
>> +	/*
>> +	 * Read the SCHIB again to verify the enablement
>> +	 */
> 
> Can be one line
> 
>> +	cc = stsch(schid, &schib);
>> +	if (cc) {
>> +		report_info("stsch: updating sch %08x failed with cc=%d",
>> +			    schid, cc);
>> +		return cc;
>> +	}
>> +
>> +	if (!(pmcw->flags & PMCW_ENABLE)) {
>> +		if (retry_count)
>> +			report_info("stsch: sch %08x successfully disabled after %d retries",
>> +				    schid, retry_count);
>> +		return 0;
>> +	}
>> +
>> +	if (retry_count++ < MAX_ENABLE_RETRIES) {
>> +		mdelay(10); /* the hardware was not ready, give it some time */
> 
> Personally I dislike comments at the end of lines except for
> constant/variable comments. Just put it before the delay.
> 
>> +		goto retry;
>> +	}
>> +
>> +	report_info("msch: modifying sch %08x failed after %d retries. pmcw flags: %04x",
>> +		    schid, retry_count, pmcw->flags);
>> +	return -1;
>> +}
>>   /*
>>    * css_enable: enable the subchannel with the specified ISC
>>    * @schid: Subchannel Identifier
>>
> 

Thanks, will do the changes
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen