On Sat, Sep 10, 2016 at 08:14:04AM +0800, Rui Wang wrote: > Is it a Romley-EP ? What kind of SNB box is it? I'll try to find one > to reproduce the problem. You don't have to - I went and analyzed it for you but it is ACPI crap and I can't be bothered to think of a solution. It looks like a chicken-and-an-egg issue where you call acpi_ioapic_add() on the root_bus and something's not initialized there in the chain of parent and children nodes. But I could very well be wrong so let me dump the details, I'll let someone else make sense of it all. Provided I've not made a mistake somewhere, which is not uncommon. So the splat is: [ 4.396872] pci_bus 0000:3f: resource 5 [mem 0x00000000-0x3fffffffffff] [ 4.403493] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 4.411331] IP: [<ffffffff8143ef8d>] acpi_ns_walk_namespace+0x3d/0x18f [ 4.417878] PGD 0 [ 4.419900] Oops: 0000 [#1] PREEMPT SMP [ 4.423731] Modules linked in: [ 4.426791] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc5+ #13 [ 4.433122] Hardware name: Dell Inc. Precision T3600/0PTTT9, BIOS A13 05/11/2014 [ 4.440506] task: ffff88043be70000 task.stack: ffffc90000020000 [ 4.446405] RIP: 0010:[<ffffffff8143ef8d>] [<ffffffff8143ef8d>] acpi_ns_walk_namespace+0x3d/0x18f [ 4.455348] RSP: 0000:ffffc90000023d98 EFLAGS: 00010202 [ 4.460641] RAX: ffffffff82dd6ae0 RBX: 0000000000000001 RCX: 0000000000000001 [ 4.467752] RDX: 00000000ffffffff RSI: 0000000000000000 RDI: 0000000000000006 [ 4.474854] RBP: ffffc90000023de8 R08: ffffffff8144bfaa R09: 0000000000000000 [ 4.481962] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 [ 4.489071] R13: ffffffff8144bfaa R14: 0000000000000000 R15: 0000000000000000 [ 4.496187] FS: 0000000000000000(0000) GS:ffff88043de00000(0000) knlGS:0000000000000000 [ 4.504242] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 4.509967] CR2: 0000000000000018 CR3: 0000000003e05000 CR4: 00000000000406f0 [ 4.517078] Stack: [ 4.519079] 0000000000000018 ffffffff82dd6c58 ffffc90000023dc0 00000001ffffffff [ 4.526476] 0000000000000006 0000000000000000 0000000000001001 ffffffff8144bfaa [ 4.533876] 0000000000000000 0000000000000000 ffffc90000023e38 ffffffff8143f51d [ 4.541273] Call Trace: [ 4.543714] [<ffffffff8144bfaa>] ? setup_res+0x94/0x94 [ 4.548915] [<ffffffff8143f51d>] acpi_walk_namespace+0x9b/0xcf [ 4.554838] [<ffffffff81fc44c1>] ? ras_debugfs_init+0x1b/0x1b [ 4.560645] [<ffffffff8144c376>] acpi_ioapic_add+0x33/0x4c [ 4.566221] [<ffffffff81faf09a>] pci_assign_unassigned_resources+0x4e/0x56 [ 4.573151] [<ffffffff81fc44df>] pcibios_assign_resources+0x1e/0xb4 [ 4.579476] [<ffffffff81fc44c1>] ? ras_debugfs_init+0x1b/0x1b [ 4.585306] [<ffffffff81000440>] do_one_initcall+0x50/0x190 [ 4.590969] [<ffffffff81f73091>] kernel_init_freeable+0x11e/0x1a6 [ 4.597130] [<ffffffff81854d60>] ? rest_init+0x140/0x140 [ 4.602506] [<ffffffff81854d6e>] kernel_init+0xe/0x110 [ 4.607735] [<ffffffff8185f11a>] ret_from_fork+0x2a/0x40 [ 4.613110] Code: 41 54 41 89 cc 53 bb 01 00 00 00 48 83 ec 28 48 83 fe ff 89 7d d0 4c 0f 44 35 58 7b 99 01 89 55 c8 45 31 ff 41 83 e4 01 89 4d cc <4d> 8b 6e 18 4c 89 45 c0 4c 89 4d b8 c7 45 d4 00 00 00 00 4d 85 [ 4.632554] RIP [<ffffffff8143ef8d>] acpi_ns_walk_namespace+0x3d/0x18f [ 4.639148] RSP <ffffc90000023d98> [ 4.642619] CR2: 0000000000000018 [ 4.645944] ---[ end trace 2fbd1c53d9becc2a ]--- [ 4.650562] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 [ 4.650562] [ 4.659694] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 You can see from the call trace how it happens: pci_assign_unassigned_resources-> acpi_ioapic_add -> ... which you added. rIP is this: ffffffff8143ef50 <acpi_ns_walk_namespace>: ffffffff8143ef50: e8 6b 16 42 00 callq ffffffff818605c0 <__fentry__> ffffffff8143ef55: 55 push %rbp ffffffff8143ef56: 48 89 e5 mov %rsp,%rbp ffffffff8143ef59: 41 57 push %r15 ffffffff8143ef5b: 41 56 push %r14 ffffffff8143ef5d: 49 89 f6 mov %rsi,%r14 ffffffff8143ef60: 41 55 push %r13 ffffffff8143ef62: 41 54 push %r12 ffffffff8143ef64: 41 89 cc mov %ecx,%r12d ffffffff8143ef67: 53 push %rbx ffffffff8143ef68: bb 01 00 00 00 mov $0x1,%ebx ffffffff8143ef6d: 48 83 ec 28 sub $0x28,%rsp ffffffff8143ef71: 48 83 fe ff cmp $0xffffffffffffffff,%rsi ffffffff8143ef75: 89 7d d0 mov %edi,-0x30(%rbp) ffffffff8143ef78: 4c 0f 44 35 58 7b 99 cmove 0x1997b58(%rip),%r14 # ffffffff82dd6ad8 <acpi_gbl_root_node> ffffffff8143ef7f: 01 ffffffff8143ef80: 89 55 c8 mov %edx,-0x38(%rbp) ffffffff8143ef83: 45 31 ff xor %r15d,%r15d ffffffff8143ef86: 41 83 e4 01 and $0x1,%r12d ffffffff8143ef8a: 89 4d cc mov %ecx,-0x34(%rbp) ffffffff8143ef8d: 4d 8b 6e 18 mov 0x18(%r14),%r13 <--- faulting insn. ffffffff8143ef91: 4c 89 45 c0 mov %r8,-0x40(%rbp) ffffffff8143ef95: 4c 89 4d b8 mov %r9,-0x48(%rbp) ffffffff8143ef99: c7 45 d4 00 00 00 00 movl $0x0,-0x2c(%rbp) ffffffff8143efa0: 4d 85 ed test %r13,%r13 In the annotated asm, this is: .globl acpi_ns_walk_namespace .type acpi_ns_walk_namespace, @function acpi_ns_walk_namespace: .LFB1454: .loc 1 191 0 .cfi_startproc .LVL5: call __fentry__ pushq %rbp # .cfi_def_cfa_offset 16 .cfi_offset 6, -16 movq %rsp, %rbp #, .cfi_def_cfa_register 6 pushq %r15 # pushq %r14 # .cfi_offset 15, -24 .cfi_offset 14, -32 movq %rsi, %r14 # start_node, start_node pushq %r13 # pushq %r12 # .cfi_offset 13, -40 .cfi_offset 12, -48 .loc 1 249 0 movl %ecx, %r12d # flags, D.24037 .loc 1 191 0 pushq %rbx # .cfi_offset 3, -56 .loc 1 213 0 movl $1, %ebx #, level .LVL6: .loc 1 191 0 subq $40, %rsp #, .loc 1 205 0 cmpq $-1, %rsi #, start_node .loc 1 191 0 movl %edi, -48(%rbp) # type, %sfp .loc 1 205 0 cmove acpi_gbl_root_node(%rip), %r14 # acpi_gbl_root_node,, start_node .LVL7: .loc 1 191 0 movl %edx, -56(%rbp) # max_depth, %sfp .loc 1 198 0 xorl %r15d, %r15d # node_previously_visited .LVL8: .loc 1 249 0 andl $1, %r12d #, D.24037 .loc 1 191 0 movl %ecx, -52(%rbp) # flags, %sfp .LBB14: .LBB15: .loc 1 79 0 movq 24(%r14), %r13 # MEM[(struct acpi_namespace_node *)start_node_1].child, start_node <--- faulting insn and the relevant piece of C code is: if (start_node == ACPI_ROOT_OBJECT) { start_node = acpi_gbl_root_node; } /* Null child means "get first node" */ parent_node = start_node; child_node = acpi_ns_get_next_node(parent_node, NULL); And parent_node, i.e., start_node is NULL here and acpi_ns_get_next_node() tries to deref it to get the child: movq 24(%r14), %r13 HTH. -- Regards/Gruss, Boris. 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