Re: [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children
From: Jerome Glisse
Date: Fri Jan 18 2019 - 15:26:30 EST
On Fri, Jan 18, 2019 at 11:58:54AM -0800, Dave Hansen wrote:
> On 1/16/19 11:16 AM, Jerome Glisse wrote:
> >> We *could* also simply truncate the existing top-level
> >> "Persistent Memory" resource and take over the released address
> >> space. But, this means that if we ever decide to hot-unplug the
> >> "RAM" and give it back, we need to recreate the original setup,
> >> which may mean going back to the BIOS tables.
> >> This should have no real effect on the existing collision
> >> detection because the areas that truly conflict should be marked
> >> IORESOURCE_BUSY.
> > Still i am worrying that this might allow device private to register
> > itself as a child of some un-busy resource as this patch obviously
> > change the behavior of register_memory_resource()
> > What about instead explicitly providing parent resource to add_memory()
> > and then to register_memory_resource() so if it is provided as an
> > argument (!NULL) then you can __request_region(arg_res, ...) otherwise
> > you keep existing code intact ?
> We don't have the locking to do this, do we? For instance, all the
> locking is done below register_memory_resource(), so any previous
> resource lookup is invalid by the time we get to register_memory_resource().
Yeah you are right, maybe just a bool then ? bool as_child