Hi Michael, On 07/11/18 at 10:49pm, Michael Ellerman wrote: > akpm@xxxxxxxxxxxxxxxxxxxx writes: > > The mm-of-the-moment snapshot 2018-07-10-16-50 has been uploaded to > > > > http://www.ozlabs.org/~akpm/mmotm/ > ... > > > * mm-sparse-add-a-static-variable-nr_present_sections.patch > > * mm-sparsemem-defer-the-ms-section_mem_map-clearing.patch > > * mm-sparsemem-defer-the-ms-section_mem_map-clearing-fix.patch > > * mm-sparse-add-a-new-parameter-data_unit_size-for-alloc_usemap_and_memmap.patch > > * mm-sparse-optimize-memmap-allocation-during-sparse_init.patch > > * mm-sparse-optimize-memmap-allocation-during-sparse_init-checkpatch-fixes.patch > > > * mm-sparse-remove-config_sparsemem_alloc_mem_map_together.patch > > This seems to be breaking my powerpc pseries qemu boots. > > The boot log with some extra debug shows eg: > > $ make pseries_le_defconfig > $ qemu-system-ppc64 -nographic -vga none -M pseries -m 2G -kernel vmlinux > vmemmap_populate f000000000000000..f000000000024000, node 0 > * f000000000000000..f000000001000000 allocated at c000000076000000 > hash__vmemmap_create_mapping: start 0xf000000000000000 size 0x1000000 phys 0x76000000 > hash__vmemmap_create_mapping: failed -1 > > <repeated many times> > > Then there's lots of other warnings about bad page states and eventually > a NULL deref and we panic(). > > > The problem seems to be that we're calling down into > hash__vmemmap_create_mapping() for every call to vmemmap_populate(), > whereas previously we would only call hash__vmemmap_create_mapping() > once because our vmemmap_populated() would return true. > > There's actually a comment in sparse_init() that says: > > * powerpc need to call sparse_init_one_section right after each > * sparse_early_mem_map_alloc, so allocate usemap_map at first. > > So changing that behaviour does seem to be the problem. > > I assume that comment is talking about the fact that we use pfn_valid() > in vmemmap_populated(). > > I'm not clear on how to fix it though. Have you tried reverting that patch and building kernel to test again? Does it work?
