No description
Find a file
Logan Gunthorpe 9db8dc6d07 PCI: Don't disable bridge BARs when assigning bus resources
Some PCI bridges implement BARs in addition to bridge windows.  For
example, here's a PLX switch:

  04:00.0 PCI bridge: PLX Technology, Inc. PEX 8724 24-Lane, 6-Port PCI
            Express Gen 3 (8 GT/s) Switch, 19 x 19mm FCBGA (rev ca)
	    (prog-if 00 [Normal decode])
      Flags: bus master, fast devsel, latency 0, IRQ 30, NUMA node 0
      Memory at 90a00000 (32-bit, non-prefetchable) [size=256K]
      Bus: primary=04, secondary=05, subordinate=0a, sec-latency=0
      I/O behind bridge: 00002000-00003fff
      Memory behind bridge: 90000000-909fffff
      Prefetchable memory behind bridge: 0000380000800000-0000380000bfffff

Previously, when the kernel assigned resource addresses (with the
pci=realloc command line parameter, for example) it could clear the struct
resource corresponding to the BAR.  When this happened, lspci would report
this BAR as "ignored":

   Region 0: Memory at <ignored> (32-bit, non-prefetchable) [size=256K]

This is because the kernel reports a zero start address and zero flags
in the corresponding sysfs resource file and in /proc/bus/pci/devices.
Investigation with 'lspci -x', however, shows the BIOS-assigned address
will still be programmed in the device's BAR registers.

It's clearly a bug that the kernel lost track of the BAR value, but in most
cases, this still won't result in a visible issue because nothing uses the
memory, so nothing is affected.  However, when an IOMMU is in use, it will
not reserve this space in the IOVA because the kernel no longer thinks the
range is valid.  (See dmar_init_reserved_ranges() for the Intel
implementation of this.)

Without the proper reserved range, a DMA mapping may allocate an IOVA that
matches a bridge BAR, which results in DMA accesses going to the BAR
instead of the intended RAM.

The problem was in pci_assign_unassigned_root_bus_resources().  When any
resource from a bridge device fails to get assigned, the code set the
resource's flags to zero.  This makes sense for bridge windows, as they
will be re-enabled later, but for regular BARs, it makes the kernel
permanently lose track of the fact that they decode address space.

Change pci_assign_unassigned_root_bus_resources() and
pci_assign_unassigned_bridge_resources() so they only clear "res->flags"
for bridge *windows*, not bridge BARs.

Fixes: da7822e5ad ("PCI: update bridge resources to get more big ranges when allocating space (again)")
Link: https://lore.kernel.org/r/20200108213208.4612-1-logang@deltatee.com
[bhelgaas: commit log, check for pci_is_bridge()]
Reported-by: Kit Chow <kchow@gigaio.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2020-01-13 13:23:02 -06:00
arch ARM fixes for 5.5-rc: 2019-12-06 16:12:39 -08:00
block block: fix memleak of bio integrity data 2019-12-05 11:38:36 -07:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-11-25 19:49:58 -08:00
Documentation powerpc updates for 5.5 #2 2019-12-06 13:36:31 -08:00
drivers PCI: Don't disable bridge BARs when assigning bus resources 2020-01-13 13:23:02 -06:00
fs 9 cifs/smb3 fixes: two timestamp fixes, one oops fix (during oplock break) for stable, two fixes found in multichannel testing, two fixes for file create when using modeforsid mount parm 2019-12-08 12:12:18 -08:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
init init/Kconfig: fix indentation 2019-12-04 19:44:13 -08:00
ipc y2038: remove CONFIG_64BIT_TIME 2019-11-15 14:38:27 +01:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
lib lib/: fix Kconfig indentation 2019-12-07 11:00:19 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'akpm' (patches from Andrew) 2019-12-05 09:46:26 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
samples samples/bpf: Fix broken xdp_rxq_info due to map order assumptions 2019-12-04 17:54:15 -08:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
security + Features 2019-12-03 12:51:35 -08:00
sound sound updates #2 for 5.5-rc1 2019-12-06 13:06:14 -08:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
usr arch: sembuf.h: make uapi asm/sembuf.h self-contained 2019-12-04 19:44:14 -08:00
virt KVM: Fix jump label out_free_* in kvm_init() 2019-11-23 11:29:17 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap Merge mainline/master into arm/fixes 2019-12-05 13:18:54 -08:00
COPYING
CREDITS Linux 5.4-rc4 2019-10-29 04:43:29 -06:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
Makefile Linux 5.5-rc1 2019-12-08 14:57:55 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

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.