Bharata B Rao <bhar...@linux.vnet.ibm.com> writes: > For a PowerKVM guest, it is possible to specify a DIMM device in > addition to the system RAM at boot time. When such a cold plugged DIMM > device is removed from a radix guest, we hit the following warning in the > guest kernel resulting in the eventual failure of memory unplug: > > remove_pud_table: unaligned range > WARNING: CPU: 3 PID: 164 at arch/powerpc/mm/pgtable-radix.c:597 > remove_pagetable+0x468/0xca0 > Call Trace: > remove_pagetable+0x464/0xca0 (unreliable) > radix__remove_section_mapping+0x24/0x40 > remove_section_mapping+0x28/0x60 > arch_remove_memory+0xcc/0x120 > remove_memory+0x1ac/0x270 > dlpar_remove_lmb+0x1ac/0x210 > dlpar_memory+0xbc4/0xeb0 > pseries_hp_work_fn+0x1a4/0x230 > process_one_work+0x1cc/0x660 > worker_thread+0xac/0x6d0 > kthread+0x16c/0x1b0 > ret_from_kernel_thread+0x5c/0x74 > > The DIMM memory that is cold plugged gets merged to the same memblock > region as RAM and hence gets mapped at 1G alignment. However since the > removal is done for one LMB (lmb size 256MB) at a time, the address > of the LMB (which is 256MB aligned) would get flagged as unaligned > in remove_pud_table() resulting in the above failure. > > This problem is not seen for hot plugged memory because for the > hot plugged memory, the mappings are created separately for each > LMB and hence they all get aligned at 256MB. > > To fix this problem for the cold plugged memory, let us mark the > cold plugged memblock region explicitly as HOTPLUGGED so that the > region doesn't get merged with RAM. All the memory that is discovered > via ibm,dynamic-memory-configuration is marked so(1). Next identify > such regions in radix_init_pgtable() and create separate mappings > within that region for each LMB so that they get don't get aligned > like RAM region at 1G (2). > > (1) For PowerKVM guests, all boot time memory is represented via > memory@XXXX nodes and hot plugged/pluggable memory is represented via > ibm,dynamic-memory-reconfiguration property. We are marking all > hotplugged memory that is in ASSIGNED state during boot as HOTPLUGGED. > With this only cold plugged memory gets marked for PowerKVM but > need to check how this will affect PowerVM guests.
Can you verify this on PowerVM too ? ie we should in most case not find anything under ibm,dynamic-memory-reconfiguration ? -aneesh