Re: [PATCH 3/3] acpi, memory-hotplug: Support getting hotplug info from SRAT.

[Tang Chen <tangchen@cn.fujitsu.com>]

On 01/29/2013 01:45 AM, Luck, Tony wrote:
>> I will post a patch to fix it. How about always keep node0 unhotpluggable ?
>
> Node 0 (or more specifically the node that contains memory<4GB) will be
> full of BIOS reserved holes in the memory map.

Hi Tony,

One thing I'm not sure, is memory<4GB always on node 0 ?
On my box, it is on node 0.

But since node id is 1-1 mapped to PXM in SRAT, if SRAT entries are not 
ordered by
physical address, memory<4GB may not on node 0. I think this is 
something related
to firmware. i didn't find anything about the order problem in ACPI 
specification.

So, do we just check if the node id != 0, or we need to check if we have 
reserved
enough for kernel, such as 4GB ?

Thanks. :)

>It probably isn't removable
> even if Linux thinks it is.  Someday we might have a smart BIOS that can
> relocate itself to another node - but for now making node0 unhotpluggable
> looks to be a plausible interim move.
>
> Ultimately we'd like to be able to remove any node (just not all of them at
> the same time ... just like we can now offline any cpu - but not all of them
> together).
>
> -Tony
>

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