Hi Serge, On Thu, Oct 06, 2016 at 12:34:15PM +0300, Serge Semin wrote: > Hello linux folks, > > Sometime ago I discovered a kernel panic popping up when PCI subsystem was > trying to enumerate PCI express bus with ASPM service enabled. Here it is: > > [ 5.089667] CPU 0 Unable to handle kernel paging request at virtual > address 00000060, epc == 80317004, ra == 80316ac8 > [ 5.120952] Oops[#1]: > ... > [ 5.528438] Call Trace: > [ 5.535640] [<80317004>] pcie_aspm_init_link_state+0x6c0/0x814 > [ 5.552843] [<80300c44>] pci_scan_slot+0x140/0x148 > [ 5.566957] [<80301dcc>] pci_scan_child_bus+0x50/0x1b0 > [ 5.582096] [<80301944>] pci_scan_bridge+0x25c/0x694 > [ 5.596724] [<80301e78>] pci_scan_child_bus+0xfc/0x1b0 > [ 5.611862] [<80301944>] pci_scan_bridge+0x25c/0x694 > [ 5.626488] [<80301e78>] pci_scan_child_bus+0xfc/0x1b0 > [ 5.641628] [<8030215c>] pci_scan_root_bus+0x64/0x124 > [ 5.656528] [<804ca298>] pcibios_scanbus+0xa8/0x188 > > I more than sure you are familiar with the issue, since I've found the > mailing discussion: "PCI: avoid NULL deref in alloc_pcie_link_state" > https://patchwork.kernel.org/patch/2751651/ > https://bugzilla.kernel.org/show_bug.cgi?id=60111 I'm trying to puzzle out a few things here. Maybe you can help me out? - Does this issue exist in current upstream kernels? Your dmesg shows a v3.19-based kernel. c8fc9339409d ("PCI/ASPM: Use dev->has_secondary_link to find downstream links"), which appeared in v4.2, fixes a problem very similar to what you're reporting. - When we dereference the NULL pointer, which device did we call pcie_aspm_init_link_state() for? - https://bugzilla.kernel.org/attachment.cgi?id=240981 is the failing dmesg log, and it shows "vgaarb: device added: PCI:0000:04:00.0". Your lspci output (https://bugzilla.kernel.org/attachment.cgi?id=241001) shows 04:00.0 is a downstream port, but vga_arbiter_add_pci_device() only prints that message for VGA class devices. https://bugzilla.kernel.org/attachment.cgi?id=240991, the successful dmesg log, shows "vgaarb: device added: PCI:0000:06:00.0". That makes more sense because 06:00.0 is class 0300, which is a VGA device. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
