Re: [Qemu-devel] [PATCH v5 6/8] hmat acpi: Build Memory Subsystem Address Range Structure(s) in ACPI HMAT

[Tao Xu <tao3.xu@intel.com>]

On 7/8/2019 5:09 PM, Igor Mammedov wrote:
> On Tue, 2 Jul 2019 16:50:24 +0800
> Tao Xu <tao3.xu@intel.com> wrote:
> 
>> On 7/1/2019 7:25 PM, Igor Mammedov wrote:
>>> On Fri, 14 Jun 2019 23:56:24 +0800
>>> Tao Xu <tao3.xu@intel.com> wrote:
>>>    
>> ...
>>>> @@ -2710,6 +2711,8 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
>>>>                acpi_add_table(table_offsets, tables_blob);
>>>>                build_slit(tables_blob, tables->linker, machine);
>>>>            }
>>>> +        acpi_add_table(table_offsets, tables_blob);
>>>> +        build_hmat(tables_blob, tables->linker, machine);
>>> I'm not sure if we should add it unconditionally.
>>> Is this table used in any meaningful manner by guest when
>>> it's incomplete (i.e. populated only with SPA records)?
>>>    
>> Hi Igor,
>>
>> In ACPI 6.2, the linux kernel use it to show the memory ranges'
>> node-id(Proximity Domain). In ACPI 6.3, the linux kernel use it to show
>> the numa node's closest initiator(Generic Initiator or Processor, directly
>> attached). It is useful for a memory only numa node, because with
>> SPA(renamed as "Memory Proximity Domain Attributes Structure" in ACPI
>> 6.3) the user-space can know the topology of hardware heterogeneous
>> memory. I think I should add a doc to describe the use case in QEMU.
> Could you point out to me the specific kernel code that parses and uses HMAT?
> 

OK, it is in drivers/acpi/hmat/hmat.c

>>
>> Therefore, the numa CLI may be lack of a input which can indicate the
>> Initiator of a memory only numa node. Dan suggested me to add a new
>> parameter for that[1].
>>
>> Maybe like:
>> -numa node,mem=4G,nodeid=2,initiator=0
>>
>> [1] https://patchwork.kernel.org/cover/10934417/
>>
>> Thanks
>>
>> Tao
>>
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