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

[Tao Xu]

On 7/8/2019 5:09 PM, Igor Mammedov wrote:
> 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?

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