Re: [kvm-unit-tests PATCH v11 8/9] s390x: css: msch, enable test

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

On 2020-07-09 13:40, Cornelia Huck wrote:
> On Thu,  9 Jul 2020 10:07:47 +0200
> Pierre Morel <pmorel@linux.ibm.com> wrote:
> 
>> A second step when testing the channel subsystem is to prepare a channel
>> for use.
>> This includes:
>> - Get the current subchannel Information Block (SCHIB) using STSCH
>> - Update it in memory to set the ENABLE bit and the specified ISC
>> - Tell the CSS that the SCHIB has been modified using MSCH
>> - Get the SCHIB from the CSS again to verify that the subchannel is
>>    enabled and uses the specified ISC.
>> - If the command succeeds but subchannel is not enabled or the ISC
>>    field is not as expected, retry a predefined retries count.
>> - If the command fails, report the failure and do not retry, even
>>    if cc indicates a busy/status pending as we do not expect this.
>>
>> This tests the MSCH instruction to enable a channel successfully.
>> Retries are done and in case of error, and if the retries count
>> is exceeded, a report is made.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> Acked-by: Thomas Huth <thuth@redhat.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>>   lib/s390x/css.h     |  8 +++--
>>   lib/s390x/css_lib.c | 72 +++++++++++++++++++++++++++++++++++++++++++++
>>   s390x/css.c         | 15 ++++++++++
>>   3 files changed, 92 insertions(+), 3 deletions(-)
> 
> (...)
> 
>> +/*
>> + * css_msch: enable subchannel and set with specified ISC
> 
> "css_enable: enable the subchannel with the specified ISC"
> 
> ?
> 
>> + * @schid: Subchannel Identifier
>> + * @isc  : number of the interruption subclass to use
>> + * Return value:
>> + *   On success: 0
>> + *   On error the CC of the faulty instruction
>> + *      or -1 if the retry count is exceeded.
>> + */
>> +int css_enable(int schid, int isc)
>> +{
>> +	struct pmcw *pmcw = &schib.pmcw;
>> +	int retry_count = 0;
>> +	uint16_t flags;
>> +	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;
>> +	}
>> +
>> +	flags = PMCW_ENABLE | (isc << PMCW_ISC_SHIFT);
>> +	if ((pmcw->flags & flags) == flags) {
> 
> I think you want (pmcw->flags & PMCW_ENABLE) == PMCW_ENABLE -- this
> catches the case of "subchannel has been enabled before, but with a
> different isc".

If with a different ISC, we need to modify the ISC.
Don't we ?

> 
>> +		report_info("stsch: sch %08x already enabled", schid);
>> +		return 0;
>> +	}



> 
> (...)
> 


-- 
Pierre Morel
IBM Lab Boeblingen