Re: [PATCH v5 14/16] hw/i386: Move arch_id decode inside x86_cpus_init

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 9 Mar 2020 14:31:31 -0500
Babu Moger <babu.moger@amd.com> wrote:

> On 3/9/20 10:21 AM, Igor Mammedov wrote:
> > On Tue, 03 Mar 2020 13:58:24 -0600
> > Babu Moger <babu.moger@amd.com> wrote:
> >   
> >> Apicid calculation depends on knowing the total number of numa nodes
> >> for EPYC cpu models. Right now, we are calculating the arch_id while
> >> parsing the numa(parse_numa). At this time, it is not known how many
> >> total numa nodes are configured in the system.
> >>
> >> Move the arch_id inside x86_cpus_init. At this time smp parameter is already
> >> completed and numa node information is available.
> >>
> >> Signed-off-by: Babu Moger <babu.moger@amd.com>
> >> ---
> >>  hw/i386/x86.c |   17 +++++++++++------
> >>  1 file changed, 11 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> >> index d46dd4ad9e..66998b065c 100644
> >> --- a/hw/i386/x86.c
> >> +++ b/hw/i386/x86.c
> >> @@ -121,6 +121,9 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
> >>      MachineState *ms = MACHINE(x86ms);
> >>      MachineClass *mc = MACHINE_GET_CLASS(x86ms);
> >>  
> >> +    /* Initialize apicid handlers first */
> >> +    cpu_x86_init_apicid_fns(ms);
> >> +
> >>      x86_cpu_set_default_version(default_cpu_version);
> >>  
> >>      /*
> >> @@ -134,6 +137,12 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
> >>      x86ms->apic_id_limit = x86_cpu_apic_id_from_index(x86ms,
> >>                                                        ms->smp.max_cpus - 1) + 1;
> >>      possible_cpus = mc->possible_cpu_arch_ids(ms);
> >> +
> >> +    for (i = 0; i < ms->smp.cpus; i++) {
> >> +        ms->possible_cpus->cpus[i].arch_id =
> >> +            x86_cpu_apic_id_from_index(x86ms, i);
> >> +    }
> >> +
> >>      for (i = 0; i < ms->smp.cpus; i++) {
> >>          x86_cpu_new(x86ms, possible_cpus->cpus[i].arch_id, &error_fatal);
> >>      }
> >> @@ -158,8 +167,7 @@ int64_t x86_get_default_cpu_node_id(const MachineState *ms, int idx)
> >>     init_topo_info(&topo_info, x86ms);
> >>  
> >>     assert(idx < ms->possible_cpus->len);
> >> -   x86ms->topo_ids_from_apicid(ms->possible_cpus->cpus[idx].arch_id,
> >> -                               &topo_info, &topo_ids);
> >> +   x86_topo_ids_from_idx(&topo_info, idx, &topo_ids);  
> > not necessary if default x86ms->topo_ids_from_apicid were initialized from x86 machine class
> > 
> > I also wonder if this default contraption we have is going to work
> > in case of EPYC cpu (i.e. is would generate valid nodeids).  
> 
> From what I understand, we call this x86_get_default_cpu_node_id only when
> the user does not specify the numa binding requirements. We tried to
> generate the default node it for a given config. This works fine for EPYC
> also. I am not sure about changing this right now. what do you think?

if it work for EPYC with default x86_topo_ids_from_idx() then it's fine.

Just keep callback here, given that callback is always initialized early (class_init)
there is no point to create mix of callback/non-callback usage.
 
> > 
> > Bot instead of than trying to fix it if it's broken,
> > I'd rather deprecate and drop get_default_cpu_node_id() requiring users
> > to explicitly define CPU mapping to numa nodes.
> > That would be consistent with req for explicit RAM for numa nodes
> > (postponed till 5.1 due to libvirt not being ready),
> > i.e if one wants numa, one should explicitly provide necessary mapping
> > or machine won't start.
> > 
> >   
> >>     return topo_ids.pkg_id % ms->numa_state->num_nodes;
> >>  }
> >>  
> >> @@ -193,10 +201,7 @@ const CPUArchIdList *x86_possible_cpu_arch_ids(MachineState *ms)
> >>  
> >>          ms->possible_cpus->cpus[i].type = ms->cpu_type;
> >>          ms->possible_cpus->cpus[i].vcpus_count = 1;
> >> -        ms->possible_cpus->cpus[i].arch_id =
> >> -            x86_cpu_apic_id_from_index(x86ms, i);
> >> -        x86ms->topo_ids_from_apicid(ms->possible_cpus->cpus[i].arch_id,
> >> -                                 &topo_info, &topo_ids);
> >> +        x86_topo_ids_from_idx(&topo_info, i, &topo_ids);  
> > ditto
> >   
> >>          ms->possible_cpus->cpus[i].props.has_socket_id = true;
> >>          ms->possible_cpus->cpus[i].props.socket_id = topo_ids.pkg_id;
> >>          if (x86ms->smp_dies > 1) {
> >>  
> >   
>