Re: [PATCH v3 07/18] machine: Add a new function init_apicid_fn in MachineClass

[Babu Moger]

On 2/3/20 9:17 AM, Igor Mammedov wrote:
> On Wed, 29 Jan 2020 10:17:11 -0600
> Babu Moger <address@hidden> wrote:
> 
>> On 1/29/20 3:14 AM, Igor Mammedov wrote:
>>> On Tue, 28 Jan 2020 13:45:31 -0600
>>> Babu Moger <address@hidden> wrote:
>>>   
>>>> On 1/28/20 10:29 AM, Igor Mammedov wrote:  
>>>>> On Tue, 03 Dec 2019 18:37:42 -0600
>>>>> Babu Moger <address@hidden> wrote:
>>>>>     
>>>>>> Add a new function init_apicid_fn in MachineClass to initialize the mode
>>>>>> specific handlers to decode the apic ids.
>>>>>>
>>>>>> Signed-off-by: Babu Moger <address@hidden>
>>>>>> ---
>>>>>>  include/hw/boards.h |    1 +
>>>>>>  vl.c                |    3 +++
>>>>>>  2 files changed, 4 insertions(+)
>>>>>>
>>>>>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>>>>>> index d4fab218e6..ce5aa365cb 100644
>>>>>> --- a/include/hw/boards.h
>>>>>> +++ b/include/hw/boards.h
>>>>>> @@ -238,6 +238,7 @@ struct MachineClass {
>>>>>>                                                           unsigned 
>>>>>> cpu_index);
>>>>>>      const CPUArchIdList *(*possible_cpu_arch_ids)(MachineState 
>>>>>> *machine);
>>>>>>      int64_t (*get_default_cpu_node_id)(const MachineState *ms, int idx);
>>>>>> +    void (*init_apicid_fn)(MachineState *ms);    
>>>>> it's x86 specific, so why it wasn put into PCMachineClass?    
>>>>
>>>> Yes. It is x86 specific for now. I tried to make it generic function so
>>>> other OSes can use it if required(like we have done in
>>>> possible_cpu_arch_ids). It initializes functions required to build the
>>>> apicid for each CPUs. We need these functions much early in the
>>>> initialization. It should be initialized before parse_numa_opts or
>>>> machine_run_board_init(in v1.c) which are called from generic context. We
>>>> cannot use PCMachineClass at this time.  
>>>
>>> could you point to specific patches in this series that require
>>> apic ids being initialized before parse_numa_opts and elaborate why?
>>>
>>> we already have possible_cpu_arch_ids() which could be called very
>>> early and calculates APIC IDs in x86 case, so why not reuse it?  
>>
>>
>> The current code(before this series) parses the numa information and then
>> sequentially builds the apicid. Both are done together.
>>
>> But this series separates the numa parsing and apicid generation. Numa
>> parsing is done first and after that the apicid is generated. Reason is we
>> need to know the number of numa nodes in advance to decode the apicid.
>>
>> Look at this patch.
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fqemu-devel%2F157541988471.46157.6587693720990965800.stgit%40naples-babu.amd.com%2F&amp;data=02%7C01%7Cbabu.moger%40amd.com%7C0a643dd978f149acf9d108d7a8bc487a%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637163398941923379&amp;sdata=sP2TnNaqNXRGEeQNhJMna3wyeBqN0XbNKqgsCTVDaOQ%3D&amp;reserved=0
>>
>> static inline apic_id_t 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->llc_id << apicid_llc_offset_epyc(topo_info)) |
>> +           (topo_ids->die_id  << apicid_die_offset(topo_info)) |
>> +           (topo_ids->core_id << apicid_core_offset(topo_info)) |
>> +           topo_ids->smt_id;
>> +}
>>
>>
>> The function apicid_from_topo_ids_epyc builds the apicid. New decode adds
>> llc_id(which is numa id here) to the current decoding. Other fields are
>> mostly remains same.
> 
> If llc_id is the same as numa id, why not reuse CpuInstanceProperties::node-id
> instead of llc_id you are adding in previous patch 6/18?
> 
I tried to use that earlier. But dropped the idea as it required some
changes. Don't remember exactly now. I am going to investigate again if we
can use the node_id for our purpose here. Will let you know if I have any
issues.