Re: [PATCH] check for s390 crypto facility availablility

[Jan Glauber <jang@linux.vnet.ibm.com>]

On Fri, 2008-07-11 at 20:29 +0800, Herbert Xu wrote: 
> On Thu, Jul 10, 2008 at 03:00:43PM +0000, Jan Glauber wrote:
> > 
> > here is a small patch for the s390 crypto detection.
> > 
> > [PATCH] respect STFL bit for s390 crypto
> > 
> > From: <jang@linux.vnet.ibm.com>
> > 
> > For all s390 in-kernel crypto algorithms we check at module
> > load time whether the CPACF facility bit is on. If the facility
> > is not enabled we bail out.
> > 
> > Signed-off-by: <jang@linux.vnet.ibm.com>
> 
> Thanks Jan, the patch looks harmless enough.
> 
> > --- ./arch/s390/crypto/crypt_s390.h.stfle
> > +++ ./arch/s390/crypto/crypt_s390.h
> > @@ -294,6 +294,10 @@ static inline int crypt_s390_func_availa
> >  	unsigned char status[16];
> >  	int ret;
> >  
> > +	/* check if CPACF facility (bit 17) is available */
> > +	if (!(stfl() & 1ULL << (31 - 17)))
> > +		return 0;
> 
> However, the patch description doesn't exactly tell me what
> happens without this check.  I mean, does the machine go up
> in flames if the check would have bailed :)

I see ;- Will resend it with a hopefully better description.

> That leads to my next question, is this something that must
> go into 2.6.26 or can it wait?

It can clearly wait for 2.6.27.

> Cheers,

thanks, Jan