Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memorymapping is specified by user [v2]

[Toshi Kani]

On Mon, 2014-01-13 at 16:53 -0800, H. Peter Anvin wrote:
> On 01/13/2014 04:33 PM, Toshi Kani wrote:
> > 
> > I do not think it makes sense.  You needed memmap=exactmap as a
> > workaround because the kernel did not boot with the firmware's memory
> > info.  So, it's broken, and you requested the kernel to ignore the
> > firmware info.
> > 
> > Why do you think memory hotplug needs to be supported under such
> > condition, which has to use the broken firmware info?
> > 
> 
> Even more than memory hotplug: what do we do with NUMA?  Since we have
> already told the kernel "the firmware is bogus" it would seem that any
> NUMA optimizations would be a bit ... cantankerous at best, no?

Agreed that NUMA info can be bogus in this case, but is probably not
critical.

In majority of the cases, memmap=exactmap is used for kdump and the
firmware info is sane.  So, I think we should keep NUMA enabled since it
could be useful when multiple CPUs are enabled for kdump.

Thanks,
-Toshi


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