Re: [PATCH kvm-unit-tests 1/2] s390x: diag288: Add missing clobber

[Janosch Frank <frankja@linux.ibm.com>]

On 12/17/21 14:47, Thomas Huth wrote:
> On 17/12/2021 11.31, Nico Boehr wrote:
>> We clobber r0 and thus should let the compiler know we're doing so.
>>
>> Because we change from basic to extended ASM, we need to change the
>> register names, as %r0 will be interpreted as a token in the assembler
>> template.
>>
>> For consistency, we align with the common style in kvm-unit-tests which
>> is just 0.
>>
>> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
>> ---
>>    s390x/diag288.c | 7 ++++---
>>    1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/s390x/diag288.c b/s390x/diag288.c
>> index 072c04a5cbd6..da7b06c365bf 100644
>> --- a/s390x/diag288.c
>> +++ b/s390x/diag288.c
>> @@ -94,11 +94,12 @@ static void test_bite(void)
>>    	/* Arm watchdog */
>>    	lc->restart_new_psw.mask = extract_psw_mask() & ~PSW_MASK_EXT;
>>    	diag288(CODE_INIT, 15, ACTION_RESTART);
>> -	asm volatile("		larl	%r0, 1f\n"
>> -		     "		stg	%r0, 424\n"
>> +	asm volatile("		larl	0, 1f\n"
>> +		     "		stg	0, 424\n"
> 
> Would it work to use %%r0 instead?

Yes, but I told him that looks weird, so that one is on me.
@claudio @thomas What's your preferred way of dealing with this?

> 
>>    		     "0:	nop\n"
>>    		     "		j	0b\n"
>> -		     "1:");
>> +		     "1:"
>> +		     : : : "0");
>>    	report_pass("restart");
>>    }
> 
> Anyway:
> Reviewed-by: Thomas Huth <thuth@redhat.com>
>