On Tue, Aug 21, 2018 at 03:17:10PM +0200, David Hildenbrand wrote: > > add_device_memory is in charge of > > I wouldn't use the terminology of onlining/offlining here. That applies > rather to memory that is exposed to the rest of the system (e.g. buddy > allocator, has underlying memory block devices). I guess it is rather a > pure setup/teardown of that device memory. Hi David, I am not sure if you are referring to: " a) calling either arch_add_memory() or add_pages(), depending on whether we want a linear mapping b) online the memory sections that correspond to the pfn range c) calling move_pfn_range_to_zone() being zone ZONE_DEVICE to expand zone/pgdat spanned pages and initialize its pages " Well, that is partialy true. I mean, in order to make this work, we need to offline/online the memory sections, because shrink_pages will rely on that from now on. Is what we do when online/offline pages, but since device memory does not go through the "official" channels, we need to do it there as well. Sure I can use another terminology, but since that is what offline/online_mem_sections do, I just came up with that. > I would really like to see the mem_hotplug_begin/end also getting moved > inside add_device_memory()/del_device_memory(). (just like for > add/remove_memory) > > I wonder if kasan_ stuff actually requires this lock, or if it could > also be somehow moved inside add_device_memory/del_device_memory. Yes, that was my first approach, but then I saw that the kasan stuff is being handled whithin those locks, so I was not sure and I backed off leaving the mem_hotplug_begin/end where they were. Maybe Jerome can shed some light and, and we can just handle the kasan stuff out of the locks. > Maybe shorten that a bit > > "HMM/devm memory does not have IORESOURCE_SYSTEM_RAM set. They use > devm_request_mem_region/devm_release_mem_region to add/release a > resource. Just back off here." Uhm, fair enough. > Any reason for these indirections? I wanted to hide the internals in the memory_hotplug code. I thought about removing them, but I finally left them. If people think that we are better off without them, I can just remove them. > I guess for readability, this patch could be split up into several > patches. E.g. factoring out of add_device_memory/del_device_memory, > release_mem_region_adjustable change ... Yes, really true. But I wanted first to gather feedback mainly from HMM/devm people to see if they saw an outright bug within the series because I am not so familiar with that part of the code. Feedback from Jerome/Dan will be appreciate as well to see if this is a good direction. But you are right, in the end, this will have to be slipt up into several parts to ease the review. Thanks for reviewing this David! I will try to address your concerns. Thanks -- Oscar Salvador SUSE L3
