Re: [kvm-unit-tests PATCH v3 2/7] s390x: Fully commit to stack save area for exceptions

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

On 3/4/21 12:37 PM, Thomas Huth wrote:
> On 22/02/2021 09.57, Janosch Frank wrote:
>> Having two sets of macros for saving registers on exceptions makes
>> maintaining harder. Also we have limited space in the lowcore to save
>> stuff and by using the stack as a save area, we can stack exceptions.
>>
>> So let's use the SAVE/RESTORE_REGS_STACK as the default. When we also
>> move the diag308 macro over we can remove the old SAVE/RESTORE_REGS
>> macros.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>> ---
> [...]
>> diff --git a/lib/s390x/asm/interrupt.h b/lib/s390x/asm/interrupt.h
>> index 1a2e2cd8..31e4766d 100644
>> --- a/lib/s390x/asm/interrupt.h
>> +++ b/lib/s390x/asm/interrupt.h
>> @@ -14,8 +14,8 @@
>>   #define EXT_IRQ_SERVICE_SIG	0x2401
>>   
>>   void register_pgm_cleanup_func(void (*f)(void));
>> -void handle_pgm_int(void);
>> -void handle_ext_int(void);
>> +void handle_pgm_int(struct stack_frame_int *stack);
>> +void handle_ext_int(struct stack_frame_int *stack);
>>   void handle_mcck_int(void);
>>   void handle_io_int(void);
> 
> So handle_io_int() does not get a *stack parameter here...
> 
>>   void handle_svc_int(void);
>> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
>> index 1ce36073..a59df80e 100644
>> --- a/lib/s390x/interrupt.c
>> +++ b/lib/s390x/interrupt.c
>> @@ -56,7 +56,7 @@ void register_pgm_cleanup_func(void (*f)(void))
>>   	pgm_cleanup_func = f;
>>   }
>>   
>> -static void fixup_pgm_int(void)
>> +static void fixup_pgm_int(struct stack_frame_int *stack)
>>   {
>>   	/* If we have an error on SIE we directly move to sie_exit */
>>   	if (lc->pgm_old_psw.addr >= (uint64_t)&sie_entry &&
>> @@ -76,7 +76,7 @@ static void fixup_pgm_int(void)
>>   		/* Handling for iep.c test case. */
>>   		if (lc->trans_exc_id & 0x80UL && lc->trans_exc_id & 0x04UL &&
>>   		    !(lc->trans_exc_id & 0x08UL))
>> -			lc->pgm_old_psw.addr = lc->sw_int_grs[14];
>> +			lc->pgm_old_psw.addr = stack->grs0[12];
> 
> I'd maybe put a "/* GR14 */" comment at the end of the line, to make it more 
> obvious which register we're aiming here at.

Will do although I'd like to extend it a bit:

/*



* We branched to the instruction that caused



* the exception so we can use the return



* address in GR14 to jump back and continue



* executing test code.



*/

> 
>>   		break;
>>   	case PGM_INT_CODE_SEGMENT_TRANSLATION:
>>   	case PGM_INT_CODE_PAGE_TRANSLATION:
>> @@ -115,7 +115,7 @@ static void fixup_pgm_int(void)
>>   	/* suppressed/terminated/completed point already at the next address */
>>   }
>>   
>> -void handle_pgm_int(void)
>> +void handle_pgm_int(struct stack_frame_int *stack)
>>   {
>>   	if (!pgm_int_expected) {
>>   		/* Force sclp_busy to false, otherwise we will loop forever */
>> @@ -130,10 +130,10 @@ void handle_pgm_int(void)
>>   	if (pgm_cleanup_func)
>>   		(*pgm_cleanup_func)();
>>   	else
>> -		fixup_pgm_int();
>> +		fixup_pgm_int(stack);
>>   }
>>   
>> -void handle_ext_int(void)
>> +void handle_ext_int(struct stack_frame_int *stack)
>>   {
>>   	if (!ext_int_expected &&
>>   	    lc->ext_int_code != EXT_IRQ_SERVICE_SIG) {
>> @@ -143,13 +143,13 @@ void handle_ext_int(void)
>>   	}
>>   
>>   	if (lc->ext_int_code == EXT_IRQ_SERVICE_SIG) {
>> -		lc->sw_int_crs[0] &= ~(1UL << 9);
>> +		stack->crs[0] &= ~(1UL << 9);
>>   		sclp_handle_ext();
>>   	} else {
>>   		ext_int_expected = false;
>>   	}
>>   
>> -	if (!(lc->sw_int_crs[0] & CR0_EXTM_MASK))
>> +	if (!(stack->crs[0] & CR0_EXTM_MASK))
>>   		lc->ext_old_psw.mask &= ~PSW_MASK_EXT;
>>   }
>>   
>> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
>> index ace0c0d9..35d20293 100644
>> --- a/s390x/cstart64.S
>> +++ b/s390x/cstart64.S
>> @@ -92,33 +92,36 @@ memsetxc:
>>   
>>   .section .text
>>   pgm_int:
>> -	SAVE_REGS
>> +	SAVE_REGS_STACK
>> +	lgr     %r2, %r15
>>   	brasl	%r14, handle_pgm_int
>> -	RESTORE_REGS
>> +	RESTORE_REGS_STACK
>>   	lpswe	GEN_LC_PGM_OLD_PSW
>>   
>>   ext_int:
>> -	SAVE_REGS
>> +	SAVE_REGS_STACK
>> +	lgr     %r2, %r15
>>   	brasl	%r14, handle_ext_int
>> -	RESTORE_REGS
>> +	RESTORE_REGS_STACK
>>   	lpswe	GEN_LC_EXT_OLD_PSW
>>   
>>   mcck_int:
>> -	SAVE_REGS
>> +	SAVE_REGS_STACK
>>   	brasl	%r14, handle_mcck_int
>> -	RESTORE_REGS
>> +	RESTORE_REGS_STACK
>>   	lpswe	GEN_LC_MCCK_OLD_PSW
>>   
>>   io_int:
>>   	SAVE_REGS_STACK
>> +	lgr     %r2, %r15
> 
> ... and here you're passing the stack pointer as a parameter, though 
> handle_io_int() does not use it... well, ok, it gets reworked again in the 
> next patch, but maybe you could still remove the above line when picking up 
> the patch?

Sure, I just fixed that up

> 
> Anyway:
> Acked-by: Thomas Huth <thuth@redhat.com>
> 
Thanks!