Re: [Qemu-devel] [Qemu-ppc] [PATCH 08/77] ppc: Add number of threads per core to the processor definition

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2015-11-16 at 16:16 +1100, David Gibson wrote:
> On Wed, Nov 11, 2015 at 11:27:21AM +1100, Benjamin Herrenschmidt
> wrote:
> > Also use it to clamp the max SMT mode and ensure that the cpu_dt_id
> > are offset by that value in order to preserve consistency with the
> > HW implementations.
> > 
> > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> 
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

In fact this is broken ;-) All the CPUs without thread get 0 in the new
field which trips at init time since we can create 0 threads :-) It
broke for example 32-bit stuff. I've fixed that in github.

> > ---
> >  target-ppc/cpu-qom.h        | 1 +
> >  target-ppc/translate_init.c | 8 +++++++-
> >  2 files changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
> > index 6967a80..fef23fd 100644
> > --- a/target-ppc/cpu-qom.h
> > +++ b/target-ppc/cpu-qom.h
> > @@ -68,6 +68,7 @@ typedef struct PowerPCCPUClass {
> >      uint32_t flags;
> >      int bfd_mach;
> >      uint32_t l1_dcache_size, l1_icache_size;
> > +    uint32_t threads_per_core;
> >  #if defined(TARGET_PPC64)
> >      const struct ppc_segment_page_sizes *sps;
> >  #endif
> > diff --git a/target-ppc/translate_init.c b/target-
> > ppc/translate_init.c
> > index c743eb1..1d402e1 100644
> > --- a/target-ppc/translate_init.c
> > +++ b/target-ppc/translate_init.c
> > @@ -8193,6 +8193,7 @@ POWERPC_FAMILY(POWER5P)(ObjectClass *oc, void
> > *data)
> >                   POWERPC_FLAG_BUS_CLK;
> >      pcc->l1_dcache_size = 0x8000;
> >      pcc->l1_icache_size = 0x10000;
> > +    pcc->threads_per_core = 2;
> >  }
> >  
> >  static void powerpc_get_compat(Object *obj, Visitor *v,
> > @@ -8339,6 +8340,7 @@ POWERPC_FAMILY(POWER7)(ObjectClass *oc, void
> > *data)
> >      pcc->l1_dcache_size = 0x8000;
> >      pcc->l1_icache_size = 0x8000;
> >      pcc->interrupts_big_endian =
> > ppc_cpu_interrupts_big_endian_lpcr;
> > +    pcc->threads_per_core = 4;
> >  }
> >  
> >  static void init_proc_POWER8(CPUPPCState *env)
> > @@ -8419,6 +8421,7 @@ POWERPC_FAMILY(POWER8)(ObjectClass *oc, void
> > *data)
> >      pcc->l1_dcache_size = 0x8000;
> >      pcc->l1_icache_size = 0x8000;
> >      pcc->interrupts_big_endian =
> > ppc_cpu_interrupts_big_endian_lpcr;
> > +    pcc->threads_per_core = 8;
> >  }
> >  #endif /* defined (TARGET_PPC64) */
> >  
> > @@ -9074,6 +9077,9 @@ static void ppc_cpu_realizefn(DeviceState
> > *dev, Error **errp)
> >  #endif
> >  
> >  #if !defined(CONFIG_USER_ONLY)
> > +    if (max_smt > pcc->threads_per_core) {
> > +        max_smt = pcc->threads_per_core;
> > +    }
> >      if (smp_threads > max_smt) {
> >          error_setg(errp, "Cannot support more than %d threads on
> > PPC with %s",
> >                     max_smt, kvm_enabled() ? "KVM" : "TCG");
> > @@ -9094,7 +9100,7 @@ static void ppc_cpu_realizefn(DeviceState
> > *dev, Error **errp)
> >      }
> >  
> >  #if !defined(CONFIG_USER_ONLY)
> > -    cpu->cpu_dt_id = (cs->cpu_index / smp_threads) * max_smt
> > +    cpu->cpu_dt_id = (cs->cpu_index / smp_threads) * pcc-
> > >threads_per_core
> >          + (cs->cpu_index % smp_threads);
> >  #endif
> >  
>