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

[Babu Moger]

On 8/20/20 7:57 AM, Igor Mammedov wrote:
> On Wed, 19 Aug 2020 17:42:58 -0500
> Babu Moger <babu.moger@amd.com> wrote:
> 
>> On 8/19/20 7:18 AM, Igor Mammedov wrote:
>>> 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://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.redhat.com%2Fshow_bug.cgi%3Fid%3D1828750&amp;data=02%7C01%7Cbabu.moger%40amd.com%7Cf7ad03f0c04d44dd104c08d84508b0b8%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637335250919794679&amp;sdata=JT8rq3Ag29WMgD8p2v2tm%2Fmdo8nBnLHb8V7QUbCHCLs%3D&amp;reserved=0
>>>> 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?  
>>
>> Yes. I am also thinking about it. We can go back to existing
>> apicid_die_width().
> 
> Given we are using die_id now, we probably can get rid of all
> topo hooks to generate apicid.

Sure. Will start working on it.  thanks

> 
>> Looking back again, I think all these code changes related to node_id is
>> causing more issues than fixes. We have added all these code to handle
>> some non- SPECed configurations like
>>  
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.redhat.com%2Fshow_bug.cgi%3Fid%3D1728166&amp;data=02%7C01%7Cbabu.moger%40amd.com%7Cf7ad03f0c04d44dd104c08d84508b0b8%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637335250919794679&amp;sdata=pOGISuQdHxFm5dEjybkGuDHfPCO1QqwE%2B%2FHR0fOAqnQ%3D&amp;reserved=0.
>>
>> Going forward it might create even more issues. Now, I think we should go
>> back and remove all these changes and just use the default decoding. Most
>> of the SPECed configuration would work just fine. With some non-SPECed
>> user inputs, it will create some sub-optimal configuration. If we can live
>> with that we will be just fine. I did not anticipate all these problems
>> when I originally started this work. Sorry, my bad.
> 
> Topology code is complex and sometimes it's easier to add a new thing,
> it's just that not every time it turns out as expected.
> We overlooked posiblilty to reuse die-id, which has lead to more
> complex and fragile outcome.
> 
> But it's fine, as long as it gets fixed in the end.

Sure. Thanks.

> 
> 
> 
>>> 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;
>>>>  
>>>>
>>>>  
>>>   
>>
>