On Thu, May 14, 2026 at 03:05:59PM +0200, Igor Mammedov wrote: > > I don't recall but I likely asked before > why not use device memory instead for it (aka DIMM device or some device > derived > from device memory object and then add e820 entry for it). > > It would be a way more simpler approach and impl. without need to resplit > anything in e820. > And no need for messing with firmware (SeaBIOS: RamSizeOver4G patch) nor EDK2. >
David previously addressed your question on the original patch version: https://lore.kernel.org/qemu-devel/[email protected]/ I wondered the same in my reply: I'm afraid it cannot be a DIMM/NVDIMM, these ranges are only described in E820 as "hotplug area". I think it must be something that's present in the memory map right from the start, where the OS would identify it as SP and treat it accordingly. We're trending towards devices being given dedicated nodes for their memory, so this actually makes sense as an extension to NUMA. While heterogenous device/memory nodes are possible - they're also pretty nonsensical outside of specifically the simple use case of: This node has both hotpluggable and not-hotpluggable memory. Which can already be accomplished another way. For a device being given a node with memory, marking it reserved or spm in e820 is needed to make the memory hotpluggable in the future (as that node has to be reserved and the hotplug memory region accounted for). Unless I am misunderstanding your feedback here - please let me know. ~Gregory
