Re: [RFC Patch V1 00/30] Enable memoryless node on x86 platforms

On Mon, Jul 21, 2014 at 10:41:59AM -0700, Tony Luck wrote:
> On Mon, Jul 21, 2014 at 10:23 AM, Nishanth Aravamudan
> <[email protected]> wrote:
> > It seems like the issue is the order of onlining of resources on a
> > specific x86 platform?
> 
> Yes. When we online a node the BIOS hits us with some ACPI hotplug events:
> 
> First: Here are some new cpus
> Next: Here is some new memory
> Last; Here are some new I/O things (PCIe root ports, PCIe devices,
> IOAPICs, IOMMUs, ...)
> 
> So there is a period where the node is memoryless - although that will generally
> be resolved when the memory hot plug event arrives ... that isn't guaranteed to
> occur (there might not be any memory on the node, or what memory there is
> may have failed self-test and been disabled).

Right, but we could 'easily' capture that in arch code and make it look
like it was done in a 'sane' order. No need to wreck the rest of the
kernel to support this particular BIOS fuckup.