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

Tony Krowiak
2018-08-10T15:50:07Z

On 08/10/2018 04:49 AM, 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.

The only case I can think of is if something is hosed and it causes an
exception. In that case, should we proceed?

>
>>>>> + */
>>>>> +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;
>>>>> +}