Re: [Qemu-devel] [RFC PATCH v2 10/15] cpu-model/s390: Add cpu class initialization routines

[Michael Mueller <mimu@linux.vnet.ibm.com>]

On Fri, 20 Feb 2015 20:21:45 +0100
Alexander Graf <agraf@suse.de> wrote:

> 
> 
> 
> > Am 20.02.2015 um 19:59 schrieb Michael Mueller <mimu@linux.vnet.ibm.com>:
> > 
> > On Fri, 20 Feb 2015 10:11:55 -0800
> > Richard Henderson <rth@twiddle.net> wrote:
> > 
> >>> +static inline uint64_t big_endian_bit(unsigned long nr)
> >>> +{
> >>> +    return 1ul << (BITS_PER_LONG - (nr % BITS_PER_LONG));
> >>> +};  
> >> 
> >> This is buggy.  NR=0 should map to 63, not 64.
> > 
> > I'm sure I was asked to replace my constant 64 and 63 with that defines and at the end I
> > messed it up... :-(
> > 
> >> 
> >>> +    return !!(*ptr & big_endian_bit(nr));  
> >> 
> >> Personally I dislike !! as an idiom.  Given that big_endian_bit isn't used
> >> anywhere else, can we integrate it and change this to
> >> 
> >> static inline int test_facility(unsigned long nr, uint64_t *fac_list)
> >> {
> >>  unsigned long word = nr / BITS_PER_LONG;
> >>  unsigned long be_bit = 63 - (nr % BITS_PER_LONG);
> >>  return (fac_list[word] >> be_bit) & 1;
> >> }
> > 
> > Yes, I just use it in this context. I will integrate your version.
> > 
> > BTW I changed the whole facility defining code to be generated by an external helper at
> > compile time. That is more simple and safe to change. I will send it with v3. See attachment
> > for an example of the generated header file.
> 
> Please make sure to use ULL with constants and uint64_t on variables. Long is almost always
> wrong in QEMU.

yep

> 
> Alex
> 
> > 
> > Thanks,
> > Michael
> > 
> > <gen-facilities.h>
>