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David Hildenbrand 7acddcc1ae mm/gup: don't implicitly set FOLL_HONOR_NUMA_FAULT 
Commit 0b9d705297 ("mm: numa: Support NUMA hinting page faults from
gup/gup_fast") from 2012 documented as the primary reason why we would want
to handle NUMA hinting faults from GUP:

  KVM secondary MMU page faults will trigger the NUMA hinting page
  faults through gup_fast -> get_user_pages -> follow_page ->
  handle_mm_fault.

That is still the case today, and relevant KVM code has been converted to
manually set FOLL_HONOR_NUMA_FAULT. So let's stop setting
FOLL_HONOR_NUMA_FAULT for all GUP users and cross fingers that not that
many other ones that really require such handling for autonuma remain.

Possible interaction with MMU notifiers:

 Assume a driver obtains a page using get_user_pages() to map it into
 a secondary MMU, and uses the MMU notifier framework to get notified on
 changes.

 Assume get_user_pages() succeeded on a PROT_NONE-mapped page (because
 FOLL_HONOR_NUMA_FAULT is not set) in an accessible VMA and the page is
 mapped into a secondary MMU. Once user space would turn that mapping
 inaccessible using mprotect(PROT_NONE), the actual PTE in the page table
 might not change. If the MMU notifier would be smart and optimize for that
 case "why notify if the PTE didn't change", that could be problematic.

 At least change_pmd_range() with MMU_NOTIFY_PROTECTION_VMA for now does an
 unconditional mmu_notifier_invalidate_range_start() ->
 mmu_notifier_invalidate_range_end() and should be fine.

 Note that even if a PTE in an accessible VMA is pte_protnone(), the
 underlying page might be accessed by a secondary MMU that does not set
 FOLL_HONOR_NUMA_FAULT, and test_young() MMU notifiers would return "true".

Link: https://lkml.kernel.org/r/20230803143208.383663-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: liubo <liubo254@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
History 2023-08-21 14:28:41 -07:00
arch merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
block block-6.5-2023-07-21 2023-07-22 11:05:15 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: algif_hash - Fix race between MORE and non-MORE sends 2023-07-08 22:48:42 +10:00
Documentation mm/ksm: add pages scanned metric 2023-08-21 13:38:02 -07:00
drivers mm,thp: fix nodeN/meminfo output alignment 2023-08-21 13:38:01 -07:00
fs merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
include merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
init mm: remove arguments of show_mem() 2023-08-18 10:12:02 -07:00
io_uring io_uring-6.5-2023-07-28 2023-07-28 10:19:44 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel memfd: replace ratcheting feature from vm.memfd_noexec with hierarchy 2023-08-21 13:37:59 -07:00
lib merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/gup: don't implicitly set FOLL_HONOR_NUMA_FAULT 2023-08-21 14:28:41 -07:00
net mm: allow per-VMA locks on file-backed VMAs 2023-08-18 10:12:51 -07:00
rust rust: error: impl Debug for Error with errname() integration 2023-06-13 01:24:42 +02:00
samples arm64: ftrace: Add direct call trampoline samples support 2023-07-10 17:51:54 -04:00
scripts x86: 2023-07-30 11:19:08 -07:00
security selinux: use vma_is_initial_stack() and vma_is_initial_heap() 2023-08-21 13:37:31 -07:00
sound ASoC: Fixes for v6.5 2023-07-27 14:54:23 +02:00
tools merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt kvm: explicitly set FOLL_HONOR_NUMA_FAULT in hva_to_pfn_slow() 2023-08-21 14:28:41 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap mailmap: update remaining active codeaurora.org email addresses 2023-07-27 13:07:05 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS - Address -Wmissing-prototype warnings 2023-06-26 16:43:54 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes 2023-08-21 14:26:20 -07:00
Makefile Linux 6.5-rc4 2023-07-30 13:23:47 -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.