FYI, we noticed the following commit: https://github.com/0day-ci/linux Arnd-Bergmann/pci-add-new-method-for-register-PCI-hosts/20160430-070604 commit 5d7f599a3b4fa1e1bcb10108ad2f728d4117aec1 ("pci: add new method for register PCI hosts") on test machine: vm-lkp-wsx03-quantal-x86_64: 2 threads qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap with 360M memory caused below changes: +------------------------------------------+------------+------------+ | | a84e2b702b | 5d7f599a3b | +------------------------------------------+------------+------------+ | boot_successes | 4 | 0 | | boot_failures | 0 | 3 | | BUG:unable_to_handle_kernel | 0 | 3 | | Oops | 0 | 3 | | RIP:pci_create_root_bus_msi | 0 | 3 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 3 | | backtrace:acpi_bus_scan | 0 | 3 | | backtrace:acpi_scan_init | 0 | 3 | | backtrace:acpi_init | 0 | 3 | | backtrace:kernel_init_freeable | 0 | 3 | +------------------------------------------+------------+------------+ [ 1.017131] acpi PNP0A03:00: _OSC: OS supports [ASPM ClockPM Segments MSI] [ 1.018786] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM [ 1.020369] acpi PNP0A03:00: fail to add MMCONFIG information, can't access extended PCI configuration space under this bridge. [ 1.023216] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 [ 1.025687] IP: [] pci_create_root_bus_msi+0xa9/0xd4 [ 1.027400] PGD 0 [ 1.028402] Oops: 0002 [#1] SMP [ 1.029675] Modules linked in: [ 1.030833] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc2-00033-g5d7f599 #1 [ 1.033064] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 1.035492] task: ffff8800139e0000 ti: ffff8800139e8000 task.ti: ffff8800139e8000 [ 1.037783] RIP: 0010:[] [] pci_create_root_bus_msi+0xa9/0xd4 [ 1.040325] RSP: 0000:ffff8800139ebbd8 EFLAGS: 00010202 [ 1.041713] RAX: 0000000000000000 RBX: ffff880012ffc400 RCX: ffff880013b2d3c0 [ 1.043368] RDX: ffff880013b2d4e0 RSI: ffff880012ffc6c8 RDI: ffff880012ffc800 [ 1.045084] RBP: ffff8800139ebc10 R08: ffff880013b2d558 R09: 0000000000000000 [ 1.046799] R10: ffffea00004ecb40 R11: 000000000000ffff R12: ffff880013b2d578 [ 1.048447] R13: ffffffff823519e0 R14: 0000000000000000 R15: 0000000000000000 [ 1.050213] FS: 0000000000000000(0000) GS:ffff880014b00000(0000) knlGS:0000000000000000 [ 1.052748] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.054242] CR2: 0000000000000008 CR3: 0000000002206000 CR4: 00000000000006e0 [ 1.056014] Stack: [ 1.056932] ffff880013b2d558 0000000000000000 ffff880013b2d540 ffff880013b29280 [ 1.059563] ffffffff82351900 ffff880013b2d558 ffff880013b2d3c0 ffff8800139ebc20 [ 1.062296] ffffffff81510071 ffff8800139ebc80 ffffffff8153beaa ffff880013b2d740 [ 1.065172] Call Trace: [ 1.066875] [] pci_create_root_bus+0x11/0x13 [ 1.068622] [] acpi_pci_root_create+0x172/0x1de [ 1.070129] [] pci_acpi_scan_root+0x15b/0x191 [ 1.071603] [] acpi_pci_root_add+0x394/0x46c [ 1.073019] [] acpi_bus_attach+0xd4/0x171 [ 1.074350] [] acpi_bus_attach+0x12e/0x171 [ 1.075646] [] acpi_bus_attach+0x12e/0x171 [ 1.077012] [] acpi_bus_scan+0x5c/0x67 [ 1.078269] [] ? acpi_sleep_proc_init+0x28/0x28 [ 1.079631] [] acpi_scan_init+0x5b/0x190 [ 1.080913] [] ? acpi_sleep_proc_init+0x28/0x28 [ 1.082334] [] acpi_init+0x274/0x291 [ 1.083563] [] do_one_initcall+0xfd/0x18f [ 1.084856] [] kernel_init_freeable+0x196/0x21e [ 1.086268] [] kernel_init+0xe/0xfd [ 1.087491] [] ret_from_fork+0x22/0x50 [ 1.088809] [] ? rest_init+0x87/0x87 [ 1.090040] Code: 4c 89 88 e8 02 00 00 49 8b 00 49 39 c0 74 27 48 8b 83 c8 02 00 00 49 8b 08 49 8b 50 08 48 89 71 08 48 89 8b c8 02 00 00 48 89 02 <48> 89 50 08 4d 89 00 4d 89 40 08 48 89 df e8 85 fb ff ff 85 c0 [ 1.099281] RIP [] pci_create_root_bus_msi+0xa9/0xd4 [ 1.100837] RSP [ 1.101905] CR2: 0000000000000008 [ 1.102903] ---[ end trace 4d306c15f7e3fb5d ]--- [ 1.104056] Kernel panic - not syncing: Fatal exception FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap -kernel /pkg/linux/x86_64-lkp/gcc-4.9/5d7f599a3b4fa1e1bcb10108ad2f728d4117aec1/vmlinuz-4.6.0-rc2-00033-g5d7f599 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-lkp-wsx03-quantal-x86_64-3/bisect_boot-1-quantal-core-x86_64.cgz-x86_64-lkp-5d7f599a3b4fa1e1bcb10108ad2f728d4117aec1-20160430-100053-yxcns7-1.yaml ARCH=x86_64 kconfig=x86_64-lkp branch=linux-devel/devel-hourly-2016043008 commit=5d7f599a3b4fa1e1bcb10108ad2f728d4117aec1 BOOT_IMAGE=/pkg/linux/x86_64-lkp/gcc-4.9/5d7f599a3b4fa1e1bcb10108ad2f728d4117aec1/vmlinuz-4.6.0-rc2-00033-g5d7f599 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-lkp-wsx03-quantal-x86_64/quantal-core-x86_64.cgz/x86_64-lkp/gcc-4.9/5d7f599a3b4fa1e1bcb10108ad2f728d4117aec1/0 LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw ip=::::vm-lkp-wsx03-quantal-x86_64-3::dhcp drbd.minor_count=8' -initrd /fs/sdc1/initrd-vm-lkp-wsx03-quantal-x86_64-3 -m 360 -smp 2 -device e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -pidfile /dev/shm/kboot/pid-vm-lkp-wsx03-quantal-x86_64-3 -serial file:/dev/shm/kboot/serial-vm-lkp-wsx03-quantal-x86_64-3 -daemonize -display none -monitor null Thanks, Kernel Test Robot