On 05/11/20 at 10:19am, David Hildenbrand wrote: > On 09.05.20 17:14, Eric W. Biederman wrote: > >>> + * If the memory layout changes, any loaded kexec image should be evicted > >>> + * as it may contain a copy of the (now stale) memory map. This also means > >>> + * we don't need to check the memory is still present when re-assembling the > >>> + * new kernel at machine_kexec() time. > >>> + */ > >> > >> Onlining/offlining is not a change of the memory map. > > > > Phrasing it that way is non-sense. What is important is memory > > available in the system. A memory map is just a reflection upon that, > > a memory map is not the definition of truth. > > > > So if this notifier reflects when memory is coming and going on the > > system this is a reasonable approach. > > > > Do these notifiers might fire for special kinds of memory that should > > only be used for very special purposes? > > > > This change with the addition of some filters say to limit taking action > > to MEM_ONLINE and MEM_OFFLINE looks reasonable to me. Probably also > > filtering out special kinds of memory that is not gernally useful. > > There are cases, where this notifier will not get called (e.g., hotplug > a DIMM and don't online it) or will get called, although nothing changed > (offline+re-online to a different zone triggered by user space). AFAIK, > nothing in kexec (*besides kdump) cares about online vs. offline memory. > This is why this feels wrong. > > add_memory()/try_remove_memory() is the place where: > - Memblocks are created/deleted (if the memblock allocator is still > alive) > - Memory resources are created/deleted (e.g., reflected in /proc/iomem) > - Firmware memmap entries are created/deleted (/sys/firmware/memmap) > > My idea would be to add something like > kexec_map_add()/kexec_map_remove() where we have > firmware_map_add_hotplug()/firmware_map_remove(). From there, we can > unload the kexec image like done in this patch. Hi David, I may miss some details, do you know why we have to unload the kexec image when add/remove memory? If this is applied, even kexec_file_load is also affected. As we discussed, kexec_file_load is not impacted by kinds of memory adding/removing at all. Besides, if unload image in casae memory added/removed, we will accept that the later 'kexec -e' is actually rebooting? Thanks Baoquan > > And these callbacks might come in handy for fixing up the kexec initial > memmap in case of kexec_file_load(). AFAIKS on x86_64: > - Hotplugging a DIMM will not add that memory to > e820_table_kexec > - Hotunplugging a DIMM will not remove that memory from e820_table_kexec > > Maybe we have similar things to handle on other architectures. > > -- > Thanks, > > David / dhildenb > >
