Re: [kvm-unit-tests PATCH v4 07/13] s390x: Use interrupts in SCLP

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On 03.01.19 13:58, Thomas Huth wrote:
> On 2019-01-03 11:08, Janosch Frank wrote:
>> We need to properly implement interrupt handling for SCLP, because on
>> z/VM and LPAR SCLP calls are not synchronous!
>>
>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
[...]
>> +
>>  static void sclp_read_scp_info(ReadInfo *ri, int length)
>>  {
>>  	unsigned int commands[] = { SCLP_CMDW_READ_SCP_INFO_FORCED,
>>  				    SCLP_CMDW_READ_SCP_INFO };
>> -	int i;
>> +	int i, cc;
>>  
>>  	for (i = 0; i < ARRAY_SIZE(commands); i++) {
>>  		memset(&ri->h, 0, sizeof(ri->h));
>>  		ri->h.length = length;
>>  
>> -		if (sclp_service_call(commands[i], ri))
>> +		sclp_mark_busy();
>> +		cc = sclp_service_call(commands[i], ri);
>> +		sclp_wait_busy();
> 
> You already do the sclp_wait_busy() in sclp_service_call now, so I think
> you don't need the sclp_wait_busy() here anymore?

Yeah, that has to go.

> 
> Also, what about moving the sclp_mark_busy() calls to the beginning of
> sclp_service_call() instead?

Wouldn't that create a race on the data of __sccb and we could end with
garbled scb commands?


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