Re: [Qemu-arm] [Qemu-devel] [PATCH v2 4/5] numa: fallback to default NUMA node instead of node 0

[Igor Mammedov]

On Fri, 26 May 2017 11:58:14 -0300
Eduardo Habkost <address@hidden> wrote:

> On Tue, May 23, 2017 at 05:44:03PM +0200, Igor Mammedov wrote:
> > On Tue, 23 May 2017 11:48:54 -0300
> > Eduardo Habkost <address@hidden> wrote:
> >   
> > > On Tue, May 23, 2017 at 04:38:49PM +0200, Igor Mammedov wrote:  
> > > > Do the same as we did in commit
> > > >   (57924bcd8 numa: introduce machine callback for VCPU to node mapping)
> > > > but only for incomplete mapping usecase, falling back to board
> > > > provided default cpu to node mapping if user hasn't provided
> > > > mapping for CPU explicitly.
> > > > 
> > > > Signed-off-by: Igor Mammedov <address@hidden>  
> > > 
> > > This breaks migration compatibility, doesn't it? I understand
> > > this use case is not supported, but if are going to break stuff
> > > for people using incomplete mappings (by rejecting the
> > > configuration on a future release), I would prefer to break it
> > > only once.  
> > it's firmware change and we generally don't care nor maintain firmware 
> > compat stuff
> > the same as with above mentioned 
> >  (57924bcd8 numa: introduce machine callback for VCPU to node mapping)  
> 
> 
> We normally keep resulting NUMA topology compatible, even if NUMA
> information is implemented only by firmware.  See how we set
> MachineClass::numa_auto_assign_ram and
> MachineClass::numa_mem_align_shift in older machine-types, for
> example.
> 
> Sometimes we didn't keep compatibility, though (e.g. on commit
> fb43b73b92 "pc: fix default VCPU to NUMA node mapping").
> 
> I wouldn't disagree with this change if we planned to support
> incomplete mappings forever.  But if we are going to remove
> support for incomplete mappings soon, I would prefer to break
> user expectations only once.
ok, I'll keep fix up to 0 and drop this patch.

> >   
> > >   
> > > > ---
> > > >  hw/core/machine.c | 3 ---
> > > >  1 file changed, 3 deletions(-)
> > > > 
> > > > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > > > index 964b75d..b8df15f 100644
> > > > --- a/hw/core/machine.c
> > > > +++ b/hw/core/machine.c
> > > > @@ -730,9 +730,6 @@ static void machine_numa_finish_init(MachineState 
> > > > *machine)
> > > >                  g_string_append_printf(s, "%sCPU %d [%s]",
> > > >                                         s->len ? ", " : "", i, cpu_str);
> > > >                  g_free(cpu_str);
> > > > -
> > > > -                /* non mapped cpus used to fallback to node 0 */
> > > > -                props.node_id = 0;
> > > >              }
> > > >  
> > > >              props.has_node_id = true;
> > > > -- 
> > > > 2.7.4
> > > >   
> > >   
> > 
> >   
>