Re: [PATCH v8 04/22] s390/zcrypt: Integrate ap_asm.h into include/asm/ap.h.

Tony Krowiak
2018-08-10T15:53:57Z

On 08/10/2018 05:37 AM, Harald Freudenberger wrote:
> On 10.08.2018 10:49, Cornelia Huck wrote:
>> On Thu, 9 Aug 2018 12:06:56 -0400
>> Tony Krowiak <akrowiak@linux.ibm.com> wrote:
>>
>>> On 08/09/2018 05:17 AM, Harald Freudenberger wrote:
>>>> On 09.08.2018 11:06, Cornelia Huck wrote:
>>>>> On Wed, 8 Aug 2018 10:44:14 -0400
>>>>> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>>>>>
>>>>>> From: Harald Freudenberger <freude@de.ibm.com>
>>>>>>
>>>>>> Move all the inline functions from the ap bus header
>>>>>> file ap_asm.h into the in-kernel api header file
>>>>>> arch/s390/include/asm/ap.h so that KVM can make use
>>>>>> of all the low level AP functions.
>>>>>>
>>>>>> Signed-off-by: Harald Freudenberger <freude@de.ibm.com>
>>>>>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>>>> You should add your own s-o-b if you are sending on patches written by
>>>>> others (even if it does not matter in the end, when they are merged
>>>>> through a different path anyway.)
>>>>>
>>>>>> ---
>>>>>> arch/s390/include/asm/ap.h | 284 ++++++++++++++++++++++++++++++++++++----
>>>>>> drivers/s390/crypto/ap_asm.h | 261 ------------------------------------
>>>>>> drivers/s390/crypto/ap_bus.c | 21 +---
>>>>>> drivers/s390/crypto/ap_bus.h | 1 +
>>>>>> drivers/s390/crypto/ap_card.c | 1 -
>>>>>> drivers/s390/crypto/ap_queue.c | 1 -
>>>>>> 6 files changed, 259 insertions(+), 310 deletions(-)
>>>>>> delete mode 100644 drivers/s390/crypto/ap_asm.h
>>>>>>
>>>>>> diff --git a/arch/s390/include/asm/ap.h b/arch/s390/include/asm/ap.h
>>>>>> index c1bedb4..046e044 100644
>>>>>> --- a/arch/s390/include/asm/ap.h
>>>>>> +++ b/arch/s390/include/asm/ap.h
>>>>>> @@ -47,6 +47,50 @@ struct ap_queue_status {
>>>>>> };
>>>>>>
>>>>>> /**
>>>>>> + * ap_intructions_available() - Test if AP instructions are available.
>>>>>> + *
>>>>>> + * Returns 0 if the AP instructions are installed.
>>>>> Stumbled over this when I was looking at the usage in patch 7: if I see
>>>>> a function called '_available' return 0, I'd assume that whatever the
>>>>> function tests for is *not* available.
>>>>>
>>>>> Rather call this function ap_instructions_check_availability() (and
>>>>> keep the return code convention), or switch this to return 0 if not
>>>>> available and !0 if available?
>>>> Good catch, Cony you are right. I'll fix this to return 1 if AP instructions
>>>> are available and 0 if not. However, this patch will come via Martin's pipe
>>>> to the Linus Torwald kernel sources.
>>> Is your intent to simply indicate whether the AP instructions are
>>> available or
>>> not; or is the intention to indicate whether the AP instructions are
>>> available
>>> and if not, they why? In the former, then I agree that a boolean should be
>>> returned; however, if the case is the latter, then what you have is fine but
>>> maybe the function name should be changed as Connie suggests.
>> So, can this actually fail for any reason other than "instructions not
>> installed"? Even if it did, the end result is that the instructions are
>> not usable -- I don't think the "why" would be interesting at that
>> point.
> I can not think of any other reason why the PQAP(TAPQ) would fail
> other than the AP instructions are not available at all. However,
> the old implementation returned -ENODEV on failure and 0 on
> success. The new implementation now returns 1 for success
> and 0 for failure. This is just one of a couple of functions related
> to ap xxx available. I'll rework them all to return a boolean value
> soon.

How would you recommend I proceed given I have functions that call this
interface that check the rc and I've had to include your patches in
this series because of that dependence?

>>>>>> + */
>>>>>> +static inline int ap_instructions_available(void)
>>>>>> +{
>>>>>> + register unsigned long reg0 asm ("0") = AP_MKQID(0, 0);
>>>>>> + register unsigned long reg1 asm ("1") = -ENODEV;
>>>>>> + register unsigned long reg2 asm ("2");
>>>>>> +
>>>>>> + asm volatile(
>>>>>> + " .long 0xb2af0000\n" /* PQAP(TAPQ) */
>>>>>> + "0: la %0,0\n"
>>>>>> + "1:\n"
>>>>>> + EX_TABLE(0b, 1b)
>>>>>> + : "+d" (reg1), "=d" (reg2)
>>>>>> + : "d" (reg0)
>>>>>> + : "cc");
>>>>>> + return reg1;
>>>>>> +}