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

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Date:   Fri, 10 Aug 2018 10:49:29 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     Harald Freudenberger <freude@...ux.ibm.com>,
        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 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.

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