On 26.06.19 10:15, Oscar Salvador wrote: > On Wed, Jun 26, 2019 at 10:11:06AM +0200, David Hildenbrand wrote: >> Back then, I already mentioned that we might have some users that >> remove_memory() they never added in a granularity it wasn't added. My >> concerns back then were never fully sorted out. >> >> arch/powerpc/platforms/powernv/memtrace.c >> >> - Will remove memory in memory block size chunks it never added >> - What if that memory resides on a DIMM added via MHP_MEMMAP_DEVICE? >> >> Will it at least bail out? Or simply break? >> >> IOW: I am not yet 100% convinced that MHP_MEMMAP_DEVICE is save to be >> introduced. > > Uhm, I will take a closer look and see if I can clear your concerns. > TBH, I did not try to use arch/powerpc/platforms/powernv/memtrace.c > yet. > > I will get back to you once I tried it out. > BTW, I consider the code in arch/powerpc/platforms/powernv/memtrace.c very ugly and dangerous. We should never allow to manually offline/online pages / hack into memory block states. What I would want to see here is rather: 1. User space offlines the blocks to be used 2. memtrace installs a hotplug notifier and hinders the blocks it wants to use from getting onlined. 3. memory is not added/removed/onlined/offlined in memtrace code. CCing the DEVs. -- Thanks, David / dhildenb
