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dingtianhong 0e40523287 PCI: fix oops when try to find Root Port for a PCI device Eric report a oops when booting the system after applying the commit `a99b646afa` ("PCI: Disable PCIe Relaxed..."): [ 4.241029] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050 [ 4.247001] IP: pci_find_pcie_root_port+0x62/0x80 [ 4.253011] PGD 0 [ 4.253011] P4D 0 [ 4.253011] [ 4.258013] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC [ 4.262015] Modules linked in: [ 4.265005] CPU: 31 PID: 1 Comm: swapper/0 Not tainted 4.13.0-dbx-DEV #316 [ 4.271002] Hardware name: Intel RML,PCH/Iota_QC_19, BIOS 2.40.0 06/22/2016 [ 4.279002] task: ffffa2ee38cfa040 task.stack: ffffa51ec0004000 [ 4.285001] RIP: 0010:pci_find_pcie_root_port+0x62/0x80 [ 4.290012] RSP: 0000:ffffa51ec0007ab8 EFLAGS: 00010246 [ 4.295003] RAX: 0000000000000000 RBX: ffffa2ee36bae000 RCX: 0000000000000006 [ 4.303002] RDX: 000000000000081c RSI: ffffa2ee38cfa8c8 RDI: ffffa2ee36bae000 [ 4.310013] RBP: ffffa51ec0007b58 R08: 0000000000000001 R09: 0000000000000000 [ 4.317001] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa51ec0007ad0 [ 4.324005] R13: ffffa2ee36bae098 R14: 0000000000000002 R15: ffffa2ee37204818 [ 4.331002] FS: 0000000000000000(0000) GS:ffffa2ee3fcc0000(0000) knlGS:0000000000000000 [ 4.339002] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 4.345001] CR2: 0000000000000050 CR3: 000000401000f000 CR4: 00000000001406e0 [ 4.351002] Call Trace: [ 4.354012] ? pci_configure_device+0x19f/0x570 [ 4.359002] ? pci_conf1_read+0xb8/0xf0 [ 4.363002] ? raw_pci_read+0x23/0x40 [ 4.366011] ? pci_read+0x2c/0x30 [ 4.370014] ? pci_read_config_word+0x67/0x70 [ 4.374012] pci_device_add+0x28/0x230 [ 4.378012] ? pci_vpd_f0_read+0x50/0x80 [ 4.382014] pci_scan_single_device+0x96/0xc0 [ 4.386012] pci_scan_slot+0x79/0xf0 [ 4.389001] pci_scan_child_bus+0x31/0x180 [ 4.394014] acpi_pci_root_create+0x1c6/0x240 [ 4.398013] pci_acpi_scan_root+0x15f/0x1b0 [ 4.402012] acpi_pci_root_add+0x2e6/0x400 [ 4.406012] ? acpi_evaluate_integer+0x37/0x60 [ 4.411002] acpi_bus_attach+0xdf/0x200 [ 4.415002] acpi_bus_attach+0x6a/0x200 [ 4.418014] acpi_bus_attach+0x6a/0x200 [ 4.422013] acpi_bus_scan+0x38/0x70 [ 4.426011] acpi_scan_init+0x10c/0x271 [ 4.429001] acpi_init+0x2fa/0x348 [ 4.433004] ? acpi_sleep_proc_init+0x2d/0x2d [ 4.437001] do_one_initcall+0x43/0x169 [ 4.441001] kernel_init_freeable+0x1d0/0x258 [ 4.445003] ? rest_init+0xe0/0xe0 [ 4.449001] kernel_init+0xe/0x150 ====================== cut here ============================= It looks like the pci_find_pcie_root_port() was trying to find the Root Port for the PCI device which is the Root Port already, it will return NULL and trigger the problem, so check the highest_pcie_bridge to fix thie problem. Fixes: `a99b646afa` ("PCI: Disable PCIe Relaxed Ordering if unsupported") Fixes: `c56d4450eb` ("PCI: Turn off Request Attributes to avoid Chelsio T5 Completion erratum") Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2017-08-15 17:25:16 -07:00
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README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.