On Tue, Jan 31, 2017 at 08:45:01PM +0000, Jayachandran C wrote:
> Commit 51ebfc92b72b4f7dac1ab45683bf56741e454b8c ("PCI: Enumerate
> switches below PCI-to-PCIe bridges") sets the has_secondary_link
> value for device type PCI_EXP_TYPE_PCIE_BRIDGE. With this change
> the function alloc_pcie_link_state() can be called with devices
> of this type as well.
You mean like this:
https://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/commit/?h=for-linus&id=672980c62c684a625fe3a688ca8c6214062d712b
Practically identical to yours :)
> On Cavium ThunderX2, this causes a crash given below:
> [ 2.794915] pci_bus 0000:00: root bus resource [bus 00-ff]
> [ 2.801569] Unable to handle kernel NULL pointer dereference at virtual address 00000090
> [ 2.809749] pgd = ffff0000094d0000
> [ 2.813178] [00000090] *pgd=0000008ffbfe0003, *pud=0000008ffbfe0003, *pmd=0000008ffbfd0003, *pte=0
> [ 2.823556] Internal error: Oops: 96000005 [#1] SMP
> [ 2.828479] Modules linked in:
> [ 2.831558] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.10.0-rc6+ #56
> [ 2.838063] Hardware name: www.cavium.com Cavium CN99XX/CN99XX, BIOS 13:17:48 Jan 19 2017
> [ 2.846326] task: ffff808f46630e00 task.stack: ffff808f4031c000
> [ 2.852309] PC is at pcie_aspm_init_link_state+0x1cc/0x868
> [ 2.857848] LR is at pcie_aspm_init_link_state+0x180/0x868
> [ 2.863387] pc : [<ffff0000084fbf8c>] lr : [<ffff0000084fbf40>] pstate: 20400049
> <...>
> [ 3.618537] [<ffff0000084fbf8c>] pcie_aspm_init_link_state+0x1cc/0x868
> [ 3.625133] [<ffff0000084e2ab4>] pci_scan_slot+0x10c/0x150
> [ 3.630672] [<ffff0000084e3c84>] pci_scan_child_bus+0x3c/0x1b0
> [ 3.636563] [<ffff0000084e38e4>] pci_scan_bridge+0x26c/0x5d0
> [ 3.642278] [<ffff0000084e3d04>] pci_scan_child_bus+0xbc/0x1b0
> [ 3.648169] [<ffff0000084e38e4>] pci_scan_bridge+0x26c/0x5d0
> [ 3.653884] [<ffff0000084e3d04>] pci_scan_child_bus+0xbc/0x1b0
> [ 3.659776] [<ffff00000853f720>] acpi_pci_root_create+0x18c/0x1f8
> [ 3.665934] [<ffff0000080972c4>] pci_acpi_scan_root+0x134/0x220
> [ 3.671912] [<ffff00000853f2b8>] acpi_pci_root_add+0x388/0x458
> [ 3.677804] [<ffff000008539d7c>] acpi_bus_attach+0xf4/0x1c4
> [ 3.683431] [<ffff000008539ddc>] acpi_bus_attach+0x154/0x1c4
> [ 3.689145] [<ffff000008539ddc>] acpi_bus_attach+0x154/0x1c4
> [ 3.694860] [<ffff000008539fc8>] acpi_bus_scan+0x80/0xac
> [ 3.700226] [<ffff000008dbd5ac>] acpi_scan_init+0xe8/0x248
> [ 3.705765] [<ffff000008dbd264>] acpi_init+0x2d4/0x344
> [ 3.710955] [<ffff00000808395c>] do_one_initcall+0x5c/0x168
> [ 3.716584] [<ffff000008d80dd0>] kernel_init_freeable+0x1ac/0x268
> [ 3.722742] [<ffff00000898d748>] kernel_init+0x18/0x110
> [ 3.728017] [<ffff0000080836b0>] ret_from_fork+0x10/0x20
> [ 3.733380] Code: 540001a0 f9400ac2 f9400842 f9401c42 (f9404842)
>
> This is caused by dereference of pdev->bus->parent->self on a device
> of type PCI_EXP_TYPE_PCIE_BRIDGE. Fix this by skipping the parent
> link state check for device type PCI_EXP_TYPE_PCIE_BRIDGE as well.
>
> Fixes: 51ebfc92b72b ("PCI: Enumerate switches below PCI-to-PCIe bridges")
> Signed-off-by: Jayachandran C <jnair@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/pci/pcie/aspm.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 17ac1dc..f631eeb 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -536,7 +536,8 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
> INIT_LIST_HEAD(&link->children);
> INIT_LIST_HEAD(&link->link);
> link->pdev = pdev;
> - if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) {
> + if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&
> + pci_pcie_type(pdev) != PCI_EXP_TYPE_PCIE_BRIDGE) {
> struct pcie_link_state *parent;
> parent = pdev->bus->parent->self->link_state;
> if (!parent) {
> --
> 2.7.4
>
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