Re: [PATCH v4 3/3] hw/i386: Remove node_id, nr_nodes and nodes_per_pkg from topology

[Igor Mammedov]

On Fri, 14 Aug 2020 16:39:40 -0500
Babu Moger <babu.moger@amd.com> wrote:

> Remove node_id, nr_nodes and nodes_per_pkg from topology. Use
> die_id, nr_dies and dies_per_pkg which is already available.
> Removes the confusion over two variables.
> 
> With node_id removed in topology the uninitialized memory issue
> with -device and CPU hotplug will be fixed.
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1828750
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
>  hw/i386/pc.c               |    1 -
>  hw/i386/x86.c              |    1 -
>  include/hw/i386/topology.h |   40 +++++++++-------------------------------
>  target/i386/cpu.c          |   11 +++--------
>  target/i386/cpu.h          |    1 -
>  5 files changed, 12 insertions(+), 42 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 47c5ca3e34..0ae5cb3af4 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1498,7 +1498,6 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
>      init_topo_info(&topo_info, x86ms);
>  
>      env->nr_dies = x86ms->smp_dies;
> -    env->nr_nodes = topo_info.nodes_per_pkg;
>      env->pkg_offset = x86ms->apicid_pkg_offset(&topo_info);
>  
>      /*
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index e90c42d2fc..4efa1f8b87 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -62,7 +62,6 @@ inline void init_topo_info(X86CPUTopoInfo *topo_info,
>  {
>      MachineState *ms = MACHINE(x86ms);
>  
> -    topo_info->nodes_per_pkg = ms->numa_state->num_nodes / ms->smp.sockets;
>      topo_info->dies_per_pkg = x86ms->smp_dies;
>      topo_info->cores_per_die = ms->smp.cores;
>      topo_info->threads_per_core = ms->smp.threads;
> diff --git a/include/hw/i386/topology.h b/include/hw/i386/topology.h
> index 07239f95f4..05ddde7ba0 100644
> --- a/include/hw/i386/topology.h
> +++ b/include/hw/i386/topology.h
> @@ -47,14 +47,12 @@ typedef uint32_t apic_id_t;
>  
>  typedef struct X86CPUTopoIDs {
>      unsigned pkg_id;
> -    unsigned node_id;
>      unsigned die_id;
>      unsigned core_id;
>      unsigned smt_id;
>  } X86CPUTopoIDs;
>  
>  typedef struct X86CPUTopoInfo {
> -    unsigned nodes_per_pkg;
>      unsigned dies_per_pkg;
>      unsigned cores_per_die;
>      unsigned threads_per_core;
> @@ -89,11 +87,6 @@ static inline unsigned apicid_die_width(X86CPUTopoInfo 
> *topo_info)
>      return apicid_bitwidth_for_count(topo_info->dies_per_pkg);
>  }
>  
> -/* Bit width of the node_id field per socket */
> -static inline unsigned apicid_node_width_epyc(X86CPUTopoInfo *topo_info)
> -{
> -    return apicid_bitwidth_for_count(MAX(topo_info->nodes_per_pkg, 1));
> -}
>  /* Bit offset of the Core_ID field
>   */
>  static inline unsigned apicid_core_offset(X86CPUTopoInfo *topo_info)
> @@ -114,30 +107,23 @@ static inline unsigned apicid_pkg_offset(X86CPUTopoInfo 
> *topo_info)
>      return apicid_die_offset(topo_info) + apicid_die_width(topo_info);
>  }
>  
> -#define NODE_ID_OFFSET 3 /* Minimum node_id offset if numa configured */
> +#define EPYC_DIE_OFFSET 3 /* Minimum die_id offset if numa configured */
                                                      ^^

from EPYC's pov NUMA is always configured, there no 'if'

but I have a question, is it possible to drop EPYC_DIE_OFFSET
and reuse apicid_die_offset(), will it break something?

The reason for question is that, we (deviating from spec)
do allow for unbound core/threads number so die_id, already could
be shifted beyound ApicId[5:4], likewise we do allow for unbound
sockets so ApicId[6] is also out of spec.
If we are fine with ApicId being encoded in these cases out of
spec, then why should we insist on DIE_OFFSET minumum at all?
Why not just allow existing apicid_die_width() to encode die_id?

In this case it will produce SPECed ApicId if user has provided
-smp that matches currently released EPYC's and in all other cases
it will be out of spec ApicId like when we set sockets/cores/trheads
to out of spec values.
  
>  /*
> - * Bit offset of the node_id field
> - *
> - * Make sure nodes_per_pkg >  0 if numa configured else zero.
> + * Bit offset of the die_id field
>   */
> -static inline unsigned apicid_node_offset_epyc(X86CPUTopoInfo *topo_info)
> +static inline unsigned apicid_die_offset_epyc(X86CPUTopoInfo *topo_info)
>  {
> -    unsigned offset = apicid_die_offset(topo_info) +
> -                      apicid_die_width(topo_info);
> +    unsigned offset = apicid_core_offset(topo_info) +
> +                      apicid_core_width(topo_info);
>  
> -    if (topo_info->nodes_per_pkg) {
> -        return MAX(NODE_ID_OFFSET, offset);
> -    } else {
> -        return offset;
> -    }
> +    return MAX(EPYC_DIE_OFFSET, offset);
>  }
>  
>  /* Bit offset of the Pkg_ID (socket ID) field */
>  static inline unsigned apicid_pkg_offset_epyc(X86CPUTopoInfo *topo_info)
>  {
> -    return apicid_node_offset_epyc(topo_info) +
> -           apicid_node_width_epyc(topo_info);
> +    return apicid_die_offset_epyc(topo_info) + apicid_die_width(topo_info);
>  }
>  
>  /*
> @@ -150,8 +136,7 @@ x86_apicid_from_topo_ids_epyc(X86CPUTopoInfo *topo_info,
>                                const X86CPUTopoIDs *topo_ids)
>  {
>      return (topo_ids->pkg_id  << apicid_pkg_offset_epyc(topo_info)) |
> -           (topo_ids->node_id << apicid_node_offset_epyc(topo_info)) |
> -           (topo_ids->die_id  << apicid_die_offset(topo_info)) |
> +           (topo_ids->die_id  << apicid_die_offset_epyc(topo_info)) |
>             (topo_ids->core_id << apicid_core_offset(topo_info)) |
>             topo_ids->smt_id;
>  }
> @@ -160,15 +145,11 @@ static inline void 
> x86_topo_ids_from_idx_epyc(X86CPUTopoInfo *topo_info,
>                                                unsigned cpu_index,
>                                                X86CPUTopoIDs *topo_ids)
>  {
> -    unsigned nr_nodes = MAX(topo_info->nodes_per_pkg, 1);
>      unsigned nr_dies = topo_info->dies_per_pkg;
>      unsigned nr_cores = topo_info->cores_per_die;
>      unsigned nr_threads = topo_info->threads_per_core;
> -    unsigned cores_per_node = DIV_ROUND_UP((nr_dies * nr_cores * nr_threads),
> -                                            nr_nodes);
>  
>      topo_ids->pkg_id = cpu_index / (nr_dies * nr_cores * nr_threads);
> -    topo_ids->node_id = (cpu_index / cores_per_node) % nr_nodes;
>      topo_ids->die_id = cpu_index / (nr_cores * nr_threads) % nr_dies;
>      topo_ids->core_id = cpu_index / nr_threads % nr_cores;
>      topo_ids->smt_id = cpu_index % nr_threads;
> @@ -188,11 +169,8 @@ static inline void 
> x86_topo_ids_from_apicid_epyc(apic_id_t apicid,
>              (apicid >> apicid_core_offset(topo_info)) &
>              ~(0xFFFFFFFFUL << apicid_core_width(topo_info));
>      topo_ids->die_id =
> -            (apicid >> apicid_die_offset(topo_info)) &
> +            (apicid >> apicid_die_offset_epyc(topo_info)) &
>              ~(0xFFFFFFFFUL << apicid_die_width(topo_info));
> -    topo_ids->node_id =
> -            (apicid >> apicid_node_offset_epyc(topo_info)) &
> -            ~(0xFFFFFFFFUL << apicid_node_width_epyc(topo_info));
>      topo_ids->pkg_id = apicid >> apicid_pkg_offset_epyc(topo_info);
>  }
>  
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index c892432cae..ba0a24f6b8 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -345,7 +345,6 @@ static void encode_cache_cpuid8000001d(CPUCacheInfo 
> *cache,
>                                         uint32_t *ecx, uint32_t *edx)
>  {
>      uint32_t l3_cores;
> -    unsigned nodes = MAX(topo_info->nodes_per_pkg, 1);
>  
>      assert(cache->size == cache->line_size * cache->associativity *
>                            cache->partitions * cache->sets);
> @@ -355,10 +354,9 @@ static void encode_cache_cpuid8000001d(CPUCacheInfo 
> *cache,
>  
>      /* L3 is shared among multiple cores */
>      if (cache->level == 3) {
> -        l3_cores = DIV_ROUND_UP((topo_info->dies_per_pkg *
> -                                 topo_info->cores_per_die *
> +        l3_cores = DIV_ROUND_UP((topo_info->cores_per_die *
>                                   topo_info->threads_per_core),
> -                                 nodes);
> +                                 topo_info->dies_per_pkg);
>          *eax |= (l3_cores - 1) << 14;
>      } else {
>          *eax |= ((topo_info->threads_per_core - 1) << 14);
> @@ -387,7 +385,6 @@ static void encode_topo_cpuid8000001e(X86CPUTopoInfo 
> *topo_info, X86CPU *cpu,
>                                         uint32_t *ecx, uint32_t *edx)
>  {
>      X86CPUTopoIDs topo_ids = {0};
> -    unsigned long nodes = MAX(topo_info->nodes_per_pkg, 1);
>  
>      x86_topo_ids_from_apicid_epyc(cpu->apic_id, topo_info, &topo_ids);
>  
> @@ -433,7 +430,7 @@ static void encode_topo_cpuid8000001e(X86CPUTopoInfo 
> *topo_info, X86CPU *cpu,
>       * NodeId is combination of node and socket_id which is already decoded
>       * in apic_id. Just use it by shifting.
>       */
> -    *ecx = ((nodes - 1) << 8) | cpu->node_id;
> +    *ecx = ((topo_info->dies_per_pkg - 1) << 8) | cpu->node_id;
>      *edx = 0;
>  }
>  
> @@ -5484,7 +5481,6 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>      uint32_t signature[3];
>      X86CPUTopoInfo topo_info;
>  
> -    topo_info.nodes_per_pkg = env->nr_nodes;
>      topo_info.dies_per_pkg = env->nr_dies;
>      topo_info.cores_per_die = cs->nr_cores;
>      topo_info.threads_per_core = cs->nr_threads;
> @@ -6944,7 +6940,6 @@ static void x86_cpu_initfn(Object *obj)
>      FeatureWord w;
>  
>      env->nr_dies = 1;
> -    env->nr_nodes = 1;
>      cpu_set_cpustate_pointers(cpu);
>  
>      object_property_add(obj, "family", "int",
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index e1a5c174dc..4c89bee8d1 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1629,7 +1629,6 @@ typedef struct CPUX86State {
>      TPRAccess tpr_access_type;
>  
>      unsigned nr_dies;
> -    unsigned nr_nodes;
>      unsigned pkg_offset;
>  } CPUX86State;
>  
> 
>