Re: [PATCH 00/18] CXL RAM and the 'Soft Reserved' => 'System RAM' default

[Dan Williams <dan.j.williams@intel.com>]

David Hildenbrand wrote:
[..]
> My concern would be that in setups with a lot of CXL memory 
> (soft-reserved), having that much offline memory during boot might make 
> the kernel run out of memory. After all, offline memory consumes memory 
> for the memmap.
> 
> Is the assumption that something like that cannot happen because we'll 
> never ever have that much soft-reserved memory? :)

Right, the assumption is that platform firmware is going to pick a
reasonable general purpose pool that lets an OS boot. In the near term
it is difficult to get that wrong since it will encompass all locally
attached DDR-DRAM. In the longer term, where it becomes possible that
all memory is CXL attached, then platform firmware will need to mark
some or all of CXL memory as general purpose (not Soft Reserved).

> Note that this is a concern only applies when not using auto-onlining in 
> the kernel during boot, which (IMHO) is or will be the default in the 
> future.

Yes, I expect that to be the default as well and let those small few
that have custom requirements figure out how to override that default.