- and I remember that PG_reserved on memory holes is relevant to
detect MMIO pages. (e.g., looking at KVM code ...)
I can see kvm_is_reserved_pfn() which checks both pfn_valid and
PageReserved. How does this help to detect memory holes though?
Any driver might be setting the page reserved.
Also is the hole inside a hotplugable memory something we really have to
care about. Has anybody actually seen a platform to require that?
That's what I was asking. I can see "support" for this was added basically
right from the beginning. I'd say we rip that out and cleanup/simplify. I am
not aware of a platform that requires this. Especially, memory holes on
DIMMs (detected during boot) seem like an unlikely thing.
The thing is that the hotplug development shows ad-hoc decisions
throughout the code. It is even worse that it is hard to guess whether
some hludges are a result of a careful design or ad-hoc trial and
failure approach on setups that never were production. Building on top
of that be preserving hacks is not going to improve the situation. So I
am perfectly fine to focus on making the most straightforward setups
work reliably. Even when there is a risk of breaking some odd setups. We
can fix them up later but we would have at least a specific example and
Alright, I'll prepare a simple patch that rejects offlining memory with
Is offlining an interesting path? I would expect onlining to be much
more interesting one.