linux-kernel - Re: [PATCH v8 04/22] s390/zcrypt: Integrate ap

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Date:   Fri, 10 Aug 2018 11:53:57 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Harald Freudenberger <freude@...ux.ibm.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com
Subject: Re: [PATCH v8 04/22] s390/zcrypt: Integrate ap_asm.h into
 include/asm/ap.h.

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@...ux.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@...ux.vnet.ibm.com> wrote:
>>>>>   
>>>>>> From: Harald Freudenberger <freude@...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@...ibm.com>
>>>>>> Signed-off-by: Christian Borntraeger <borntraeger@...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;
>>>>>> +}