On Wed, Jan 27, 2021 at 04:03:00PM +0100, Andreas Larsson wrote: > > > Commit cca079ef8ac29a7c02192d2bad2ffe4c0c5ffdd0 makes sparc32 use > memblocks instead of the previous bootmem solution. Unfortunately, due > to this: > > #define PAGE_OFFSET 0xf0000000 > #define __va(x) ((void *)((unsigned long) (x) - phys_base + > PAGE_OFFSET)) > #define phys_to_virt __va > > it makes physical addresses >= 0x10000000 past phys_base wrap around the > 32-bit memory space when converted to virtual addresses, e.g. in > memblock_alloc_try_nid. Physical memory exactly 0x10000000 past > phys_base is returned as an unintended NULL pointer, leading to a panic > in my boot when percpu memory allocation fails due to it. > > Unfortunately I have had 256 MB memory or less in a lot of my testing, > so this old one has slipped by me. > > Does anyone has any ideas or pointers on how to resolve this? I think the simplest way to work around this is to limit early allocations to 256M with addition of memblock_set_current_limit(SZ_256M); somewhere at setup_arch(). The page allocator will anyway see the entire memory, so I cannot think of any downside here. > Example follows where I have 512 MB memory at 0x40000000: > > ----->%>%>%>%----- > memblock_add: [0x40000000-0x5fffafff] bootmem_init+0x1f8/0x210 > 319MB HIGHMEM available. > memblock_reserve: [0x40000000-0x40e71fff] bootmem_init+0x178/0x210 > memblock_add: [0x40000000-0x40e71fff] bootmem_init+0x188/0x210 > memblock_alloc_try_nid: 5242880 bytes align=0x40000 nid=-1 from=0x00000000 > max_addr=0x00000000 srmmu_nocache_init+0x20/0x25c > memblock_reserve: [0x40e80000-0x4137ffff] > memblock_alloc_range_nid+0xcc/0x178 > memblock_alloc_try_nid: 2560 bytes align=0x20 nid=-1 from=0x00000000 > max_addr=0x00000000 srmmu_nocache_init+0x94/0x25c > memblock_reserve: [0x40e72000-0x40e729ff] > memblock_alloc_range_nid+0xcc/0x178 > memblock_alloc_try_nid: 4096 bytes align=0x20 nid=-1 from=0x00000000 > max_addr=0x00000000 sparc_context_init+0x1c/0xe4 > memblock_reserve: [0x40e72a00-0x40e739ff] > memblock_alloc_range_nid+0xcc/0x178 > Zone ranges: > DMA [mem 0x0000000040000000-0x000000004bffffff] > Normal empty > HighMem [mem 0x000000004c000000-0x000000005fffafff] > Movable zone start for each node > Early memory node ranges > node 0: [mem 0x0000000040000000-0x000000005fffafff] > Initmem setup node 0 [mem 0x0000000040000000-0x000000005fffafff] > ----->%>%>%>%----- > > then much much later memblock_alloc_internal gets 0x50000000 from > memblock_alloc_range_nid and returns a NULL pointer as result of > phys_to_virt. > > ----->%>%>%>%----- > memblock_alloc_try_nid: 40960 bytes align=0x1000 nid=-1 from=0x4fffffff > max_addr=0x00000000 pcpu_dfl_fc_alloc+0x28/0x40 > memblock_reserve: [0x50000000-0x50009fff] > memblock_alloc_range_nid+0xcc/0x178 > memblock_free: [0x40e7e000-0x40e7efff] pcpu_free_alloc_info+0x1c/0x30 > memblock_free: [0x40e7f000-0x40e7ffff] pcpu_embed_first_chunk+0x194/0x3b8 > Kernel panic - not syncing: Failed to initialize percpu areas. > CPU: 0 PID: 0 Comm: swapper Not tainted 5.11.0-rc3-00040-gbc4547251e1-dirty > #28 > ----->%>%>%>%----- > > Adding mem=256M to the command line solves the panic problem but makes > the extra memory not be available for normal allocation later on either. > > The two first memblock_add calls (seen in the first first set of > outputs) with overlapping address ranges that is done in bootmem_init > also looks a bit worrying, but removing the second one does not affect > this problem. > > -- > Best regards, > > Andreas Larsson > Cobham Gaisler -- Sincerely yours, Mike.
