Re: [kvm-unit-tests PATCH v7 4/4] s390x: SCLP unit test

[David Hildenbrand <david@redhat.com>]

On 13.01.20 15:05, Claudio Imbrenda wrote:
> On Mon, 13 Jan 2020 14:10:10 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
> [...]
> 
>> :) I'm confused by the fact that you "expect_pgm_int()" but actually
>> don't expect one ...
>>
>> Please enlighten me why this isn't
>>
>> +	sclp_mark_busy();
>> +	h->length = 8;
>> +	sclp_setup_int();
>> +
>> +	asm volatile(
>> +		"       .insn   rre,0xb2204200,%1,%2\n"  /* servc
>> %1,%2 */
>> +		"       ipm     %0\n"
>> +		"       srl     %0,28"
>> +		: "=&d" (cc) : "d" (valid_code), "a" (__pa(pagebuf))
>> +		: "cc", "memory");
>> +	if (!cc)
>> +		sclp_wait_busy();
>> +	report(cc == 0, "Instruction format ignored bits");
>>
>> I feel like I am missing something important.
> 
> because if we take an unexpected pgm interrupt:
> * the interrupt handler will write stuff on the console using SCLP
> * it will wait for the busy flag to be cleared before doing so
> * thus it will hang.
> 
> this would be solved by adding special logic to the pgm interrupt
> handler (as we have discussed in your previous email)
> 

I see, so the issue should hold for all SCLP checks where we don't
expect an exception ... hmmm

-- 
Thanks,

David / dhildenb