Re: CXL Boot to Bash - Section 3: Memory (block) Hotplug

[Oscar Salvador]

On Tue, Mar 11, 2025 at 12:08:03PM -0400, Zi Yan wrote:
> Or a new option for memmap_on_memory like “use_whole_block”, then hotplug
> code checks altmap is NULL or not when a memory block is plugged.
> If altmap is NULL, the hot plugged memory block is used as memmap,
> otherwise, the memory block is plugged as normal memory. The code also
> needs to maintain which part of the altmap is used to tell whether
> the memmap’d memory block can be offline or not.

One of the first versions of memmap_on_memory did not have the restrictions of
working only per memblock, so one could hot-plug more than a memory-block worth
of memory using memmap_on_memory, meaning that we could end up with memblocks
only containing memmap pages.

Now, we decided to go with only one memblock at a time because of simplicity
and also because we did not have any real-world scenarios that needed that
besides being able to have larger contiguos memory for e.g: hugetlb.

If people think that there is more to it, we could revisit that and see how it
would look nowadays. Maybe it is not too much of a surgery. (or maybe it is :-))
 

-- 
Oscar Salvador
SUSE Labs