On Mon, 2019-07-29 at 10:06 +0200, David Hildenbrand wrote: > > > Of course, other interfaces might make sense. > > > > > > You can then start using these memory blocks and hinder them from > > > getting onlined (as a safety net) via memory notifiers. > > > > > > That would at least avoid you having to call > > > add_memory/remove_memory/offline_pages/device_online/modifying > > > memblock > > > states manually. > > > > I see what you're saying and that definitely sounds safer. > > > > We would still need to call remove_memory and add_memory from > > memtrace > > as > > just offlining memory doesn't remove it from the linear page tables > > (if > > it's still in the page tables then hardware can prefetch it and if > > hardware tracing is using it then the box checkstops). > > That prefetching part is interesting (and nasty as well). If we could > at > least get rid of the manual onlining/offlining, I would be able to > sleep > better at night ;) One step at a time. >
What are your thoughts on adding remove to state_store in drivers/base/memory.c? And an accompanying add? So then userspace could do "echo remove > memory34/state"? Then most of the memtrace code could be moved to a userspace tool. The only bit that we would need to keep in the kernel is setting up debugfs files in memtrace_init_debugfs.
