The source for the Linux kernel used in Windows Subsystem for Linux 2 (WSL2)
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Alistair Popple b756a3b5e7 mm: device exclusive memory access
Some devices require exclusive write access to shared virtual memory (SVM)
ranges to perform atomic operations on that memory.  This requires CPU
page tables to be updated to deny access whilst atomic operations are
occurring.

In order to do this introduce a new swap entry type
(SWP_DEVICE_EXCLUSIVE).  When a SVM range needs to be marked for exclusive
access by a device all page table mappings for the particular range are
replaced with device exclusive swap entries.  This causes any CPU access
to the page to result in a fault.

Faults are resovled by replacing the faulting entry with the original
mapping.  This results in MMU notifiers being called which a driver uses
to update access permissions such as revoking atomic access.  After
notifiers have been called the device will no longer have exclusive access
to the region.

Walking of the page tables to find the target pages is handled by
get_user_pages() rather than a direct page table walk.  A direct page
table walk similar to what migrate_vma_collect()/unmap() does could also
have been utilised.  However this resulted in more code similar in
functionality to what get_user_pages() provides as page faulting is
required to make the PTEs present and to break COW.

[dan.carpenter@oracle.com: fix signedness bug in make_device_exclusive_range()]
  Link: https://lkml.kernel.org/r/YNIz5NVnZ5GiZ3u1@mwanda

Link: https://lkml.kernel.org/r/20210616105937.23201-8-apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-01 11:06:03 -07:00
Documentation mm: device exclusive memory access 2021-07-01 11:06:03 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
arch mm: remove special swap entry functions 2021-07-01 11:06:03 -07:00
block block-5.13-2021-05-22 2021-05-22 07:40:34 -10:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto async_xor: check src_offs is not NULL before updating it 2021-06-10 19:40:14 -07:00
drivers mm: rename migrate_pgmap_owner 2021-07-01 11:06:03 -07:00
fs mm: remove special swap entry functions 2021-07-01 11:06:03 -07:00
include mm: device exclusive memory access 2021-07-01 11:06:03 -07:00
init pid: take a reference when initializing `cad_pid` 2021-06-05 08:58:11 -07:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel mm: replace CONFIG_FLAT_NODE_MEM_MAP with CONFIG_FLATMEM 2021-06-29 10:53:55 -07:00
lib mm: rename migrate_pgmap_owner 2021-07-01 11:06:03 -07:00
mm mm: device exclusive memory access 2021-07-01 11:06:03 -07:00
net net/ipv5/tcp: use vma_lookup() in tcp_zerocopy_receive() 2021-06-29 10:53:51 -07:00
samples VFIO fixes for v5.13-rc5 2021-06-03 11:52:24 -07:00
scripts kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21 2021-06-29 10:53:54 -07:00
security trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
sound ASoC: rt5645: Avoid upgrading static warnings to errors 2021-06-24 12:22:27 +02:00
tools selftests/vm: add test for MADV_POPULATE_(READ|WRITE) 2021-06-30 20:47:31 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt virt/kvm: use vma_lookup() instead of find_vma_intersection() 2021-06-29 10:53:51 -07:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Marek's other e-mail address and identity without diacritics 2021-06-24 19:40:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
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 MAINTAINERS: add tools/testing/selftests/vm/ to MEMORY MANAGEMENT 2021-06-30 20:47:30 -07:00
Makefile Linux 5.13 2021-06-27 15:21:11 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README

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.