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

[Igor Mammedov]

On Tue, 2 Jul 2019 16:50:24 +0800
Tao Xu <address@hidden> wrote:

> On 7/1/2019 7:25 PM, Igor Mammedov wrote:
> > On Fri, 14 Jun 2019 23:56:24 +0800
> > Tao Xu <address@hidden> 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?

> 
> 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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