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Alex Williamson bc93b9ae01 vfio-pci: Avoid recursive read-lock usage
A down_read on memory_lock is held when performing read/write accesses
to MMIO BAR space, including across the copy_to/from_user() callouts
which may fault.  If the user buffer for these copies resides in an
mmap of device MMIO space, the mmap fault handler will acquire a
recursive read-lock on memory_lock.  Avoid this by reducing the lock
granularity.  Sequential accesses requiring multiple ioread/iowrite
cycles are expected to be rare, therefore typical accesses should not
see additional overhead.

VGA MMIO accesses are expected to be non-fatal regardless of the PCI
memory enable bit to allow legacy probing, this behavior remains with
a comment added.  ioeventfds are now included in memory access testing,
with writes dropped while memory space is disabled.

Fixes: abafbc551f ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory")
Reported-by: Zhiyi Guo <zhguo@redhat.com>
Tested-by: Zhiyi Guo <zhguo@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
2020-08-17 11:08:18 -06:00
arch parisc: fix PMD pages allocation by restoring pmd_alloc_one() 2020-08-16 10:53:13 -07:00
block block-5.9-2020-08-14 2020-08-15 20:36:42 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-14 13:09:15 -07:00
Documentation Misc fixes and small updates all around the place: 2020-08-15 10:38:03 -07:00
drivers vfio-pci: Avoid recursive read-lock usage 2020-08-17 11:08:18 -06:00
fs io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
include io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
init OpenRISC updates for 5.9 2020-08-14 14:04:53 -07:00
ipc ipc/shm.c: remove the superfluous break 2020-08-12 10:58:02 -07:00
kernel io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
lib iomap: constify ioreadX() iomem argument (as in generic implementation) 2020-08-14 19:56:57 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'akpm' (patches from Andrew) 2020-08-15 08:02:03 -07:00
net 9p pull request for inclusion in 5.9 2020-08-15 08:34:36 -07:00
samples Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
scripts Kconfig updates for v5.9 2020-08-14 11:04:45 -07:00
security Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
sound sound fixes for 5.9-rc1 2020-08-14 15:58:57 -07:00
tools Cleanup, SECCOMP_FILTER support, message printing fixes, and other 2020-08-15 18:50:32 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +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 .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap mailmap: add entry for Greg Kurz 2020-08-14 19:56:56 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS perf tools changes for v5.9: 2nd batch 2020-08-15 11:17:15 -07:00
Makefile Linux 5.9-rc1 2020-08-16 13:04:57 -07:00
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.