Re: [Qemu-ppc] [Qemu-devel] [PATCH for 2.13] spapr: Correct max associativity domains value for non-NUMA configs

[David Gibson]

On Tue, Apr 17, 2018 at 07:17:51PM +0200, Greg Kurz wrote:
> Cc'ing David who should always be in the recipient list when posting ppc 
> related
> patches :)
> 
> On Tue, 17 Apr 2018 12:21:35 -0400
> Serhii Popovych <address@hidden> wrote:
> 
> > In non-NUMA configurations nb_numa_nodes is zero and we set 5th cell
> > in ibm,max-associativity-domains to -1. That causes to stall Linux
> > guests during boot after following line:
> > 
> > [    0.000000] NUMA associativity depth for CPU/Memory: 4
> > 
> > Make last possible NUMA in property zero to correct support for
> > non-NUMA guests.
> > 
> 
> Alternatively, as suggested by David in some other mail, you could drop the
> property in this case. I've checked it fixes the hang too, and it probably
> makes more sense than exposing only zeroes.

Actually, I think this is the better solution. qemu treats "not NUMA"
and "exactly one NUMA node" differently for historical reasons, but I
don't think that actually makes a whole lot of sense.  I think
advertising them identically so we don't generate more special cases
on the guest side is a better idea.

> > Fixes: c1df49a670ef ("spapr: Add ibm,max-associativity-domains property")
> 
> Since c1df49a670ef hasn't hit master yet, I guess we should squash this
> patch (or any alternative) there to preserve bisect, ie, either David
> does it for you or you post a v4 of your previous series.

Right, I've folded these together in my tree so we don't get an
interval of broken commits.

> 
> > Signed-off-by: Serhii Popovych <address@hidden>
> > ---
> >  hw/ppc/spapr.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 7b2bc4e..bff2125 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -914,7 +914,7 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr, 
> > void *fdt)
> >          cpu_to_be32(0),
> >          cpu_to_be32(0),
> >          cpu_to_be32(0),
> > -        cpu_to_be32(nb_numa_nodes - 1),
> > +        cpu_to_be32(nb_numa_nodes ? nb_numa_nodes - 1 : 0),
> >      };
> >  
> >      _FDT(rtas = fdt_add_subnode(fdt, 0, "rtas"));
> 
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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