Re: [PATCH v2] s390/ap: Support new APMLM field with PQAP/TAPQ instruction

[Harald Freudenberger <freude@linux.ibm.com>]

On 2026-10-07 16:05, Finn Callies wrote:
> On 06.10.26 16:58, Harald Freudenberger wrote:
>> There is a new field APMLM (AP message limit multiplier) defined
>> within the GR2 register on successful invocation of the TAPQ
>> subfunction for the PQAP instruction.
>> 
>> So the new formula to calculate the AP max message limit is now:
>> 
>>    if ml field <= 3
>>      AP max message limit is 12KB
>>    else
>>      AP max message limit = apml * (apmlm + 1) * 4KB
> 
> As per architecture it is more like:
> 
> if apml < 3 && apmlm == 0
> 	mapml = 12k
> else if apmlm == 0
> 	mapml = apml * 4k
this
> else if apml > 0
> 	mapml = apml * (apmlm + 1) * 4k
and this come to the same result.
And for ampl == 3 the formula results in 12KB,
> else
> 	// undefined
and this else is unreachable.
> 
> But yours is effectively the same.
Yep
> 
>> 
>> Also adapt the HWINFO mask to have this new apmlm field shine
>> through this bit filter mask.
>> 
>> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
>> ---
>>   arch/s390/include/asm/ap.h    | 4 ++--
>>   drivers/s390/crypto/ap_bus.h  | 2 +-
>>   drivers/s390/crypto/ap_card.c | 3 ++-
>>   3 files changed, 5 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch/s390/include/asm/ap.h b/arch/s390/include/asm/ap.h
>> index c91b6ace199d..01d575c35887 100644
>> --- a/arch/s390/include/asm/ap.h
>> +++ b/arch/s390/include/asm/ap.h
>> @@ -123,8 +123,8 @@ struct ap_tapq_hwinfo {
>>   			unsigned int	   : 14;
>>   			unsigned int at	   :  8; /* ap type */
>>   			unsigned int nd	   :  8; /* nr of domains */
>> -			unsigned int	   :  4;
>> -			unsigned int ml	   :  4; /* apxl ml */
>> +			unsigned int mlm   :  4; /* AP msg limit multiplier */
>> +			unsigned int ml	   :  4; /* AP msg limit */
>>   			unsigned int	   :  3;
>>   			unsigned int qd	   :  5; /* queue depth */
>>   		};
>> diff --git a/drivers/s390/crypto/ap_bus.h 
>> b/drivers/s390/crypto/ap_bus.h
>> index fb4d678336e4..34f9dcd96bc7 100644
>> --- a/drivers/s390/crypto/ap_bus.h
>> +++ b/drivers/s390/crypto/ap_bus.h
>> @@ -181,7 +181,7 @@ struct ap_card {
>>   	bool chkstop;			/* checkstop state */
>>   };
>>   -#define TAPQ_CARD_HWINFO_MASK 0xFFFF0000FFFF0F1FUL
>> +#define TAPQ_CARD_HWINFO_MASK 0xFFFF0000FFFFFF1FUL
>>   #define ASSOC_IDX_INVALID 0x10000
>>     #define to_ap_card(x) container_of((x), struct ap_card, 
>> ap_dev.device)
>> diff --git a/drivers/s390/crypto/ap_card.c 
>> b/drivers/s390/crypto/ap_card.c
>> index c86397f4ddcd..e9a8180f08c2 100644
>> --- a/drivers/s390/crypto/ap_card.c
>> +++ b/drivers/s390/crypto/ap_card.c
>> @@ -242,7 +242,8 @@ struct ap_card *ap_card_create(int id, struct 
>> ap_tapq_hwinfo hwinfo,
>>   	ac->hwinfo = hwinfo;
>>   	ac->id = id;
>>   	ac->maxmsgsize = hwinfo.ml > 3 ?
>> -		hwinfo.ml * AP_TAPQ_ML_FIELD_CHUNK_SIZE : AP_DEFAULT_MAX_MSG_SIZE;
>> +		hwinfo.ml * (hwinfo.mlm + 1) * AP_TAPQ_ML_FIELD_CHUNK_SIZE :
>> +		AP_DEFAULT_MAX_MSG_SIZE;
>>     	return ac;
>>   }
> 
> Reviewed-by: Finn Callies <fcallies@linux.ibm.com>
> 
> Have you tested it with your qemu support or my mocking?

Still untested. I am about to test this in my qemu AP emulation soon.