Dear stable kernel maintainers, can you please apply this patch to all 3.x and 4.x stable kernels? Based on upstream commit bf71bc16e02162388808949b179d59d0b571b965 which doesn't apply out of the box on older kernels. ----------- The Debian kernel v5.6 triggers this kernel panic: Kernel panic - not syncing: Bad Address (null pointer deref?) Bad Address (null pointer deref?): Code=26 (Data memory access rights trap) at addr 0000000000000000 CPU: 0 PID: 0 Comm: swapper Not tainted 5.6.0-2-parisc64 #1 Debian 5.6.14-1 IAOQ[0]: mem_init+0xb0/0x150 IAOQ[1]: mem_init+0xb4/0x150 RP(r2): start_kernel+0x6c8/0x1190 Backtrace: [<0000000040101ab4>] start_kernel+0x6c8/0x1190 [<0000000040108574>] start_parisc+0x158/0x1b8 on a HP-PARISC rp3440 machine with this memory layout: Memory Ranges: 0) Start 0x0000000000000000 End 0x000000003fffffff Size 1024 MB 1) Start 0x0000004040000000 End 0x00000040ffdfffff Size 3070 MB Fix the crash by avoiding virt_to_page() and similar functions in mem_init() until the memory zones have been fully set up. Signed-off-by: Helge Deller <deller@xxxxxx> diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c index aae9b0d71c1e..10a52664e29f 100644 --- a/arch/parisc/mm/init.c +++ b/arch/parisc/mm/init.c @@ -607,7 +607,7 @@ void __init mem_init(void) > BITS_PER_LONG); high_memory = __va((max_pfn << PAGE_SHIFT)); - set_max_mapnr(page_to_pfn(virt_to_page(high_memory - 1)) + 1); + set_max_mapnr(max_low_pfn); free_all_bootmem(); #ifdef CONFIG_PA11
