Re: [Qemu-devel] [RFC v2 PATCH 08/13] tcg/s390: Add support for fence

[Richard Henderson]

On 06/02/2016 12:31 PM, Sergey Fedorov wrote:
> On 31/05/16 21:39, Pranith Kumar wrote:
> > Cc: Alexander Graf <address@hidden>
> > Signed-off-by: Richard Henderson <address@hidden>
> > Signed-off-by: Pranith Kumar <address@hidden>
> > ---
> >  tcg/s390/tcg-target.inc.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/tcg/s390/tcg-target.inc.c b/tcg/s390/tcg-target.inc.c
> > index e95b04b..b4f14bc 100644
> > --- a/tcg/s390/tcg-target.inc.c
> > +++ b/tcg/s390/tcg-target.inc.c
> > @@ -341,6 +341,7 @@ static tcg_insn_unit *tb_ret_addr;
> >  #define FACILITY_EXT_IMM       (1ULL << (63 - 21))
> >  #define FACILITY_GEN_INST_EXT  (1ULL << (63 - 34))
> >  #define FACILITY_LOAD_ON_COND   (1ULL << (63 - 45))
> > +#define FACILITY_FAST_BCR_SER   FACILITY_LOAD_ON_COND
> >
> >  static uint64_t facilities;
> >
> > @@ -2157,6 +2158,13 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode 
> > opc,
> >          tgen_deposit(s, args[0], args[2], args[3], args[4]);
> >          break;
> >
> > +    case INDEX_op_mb:
> > +        /* The host memory model is quite strong, we simply need to
> > +           serialize the instruction stream.  */
> > +        tcg_out_insn(s, RR, BCR,
> > +                    facilities & FACILITY_FAST_BCR_SER ? 14 : 15, 0);
> > +        break;
> > +
>
> Do we? What does that mean?

It's the difference between ACQ_REL and SEQ_CST for s390x.  FWIW.


r~