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Jason Gunthorpe 71fb40ae9b drm/ttm: remove ttm_bo_vm_insert_huge() 
[ Upstream commit 0d97950953 ]

The huge page functionality in TTM does not work safely because PUD and
PMD entries do not have a special bit.

get_user_pages_fast() considers any page that passed pmd_huge() as
usable:

	if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
		     pmd_devmap(pmd))) {

And vmf_insert_pfn_pmd_prot() unconditionally sets

	entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));

eg on x86 the page will be _PAGE_PRESENT | PAGE_PSE.

As such gup_huge_pmd() will try to deref a struct page:

	head = try_grab_compound_head(pmd_page(orig), refs, flags);

and thus crash.

Thomas further notices that the drivers are not expecting the struct page
to be used by anything - in particular the refcount incr above will cause
them to malfunction.

Thus everything about this is not able to fully work correctly considering
GUP_fast. Delete it entirely. It can return someday along with a proper
PMD/PUD_SPECIAL bit in the page table itself to gate GUP_fast.

Fixes: 314b6580ad ("drm/ttm, drm/vmwgfx: Support huge TTM pagefaults")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Thomas Hellström <thomas.helllstrom@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
[danvet: Update subject per Thomas' &Christian's review]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/0-v2-a44694790652+4ac-ttm_pmd_jgg@nvidia.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-11-18 19:17:08 +01:00
arch openrisc: fix SMP tlb flush NULL pointer dereference 2021-11-18 19:17:06 +01:00
block block: fix device_add_disk() kobject_create_and_add() error handling 2021-11-18 19:17:08 +01:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-18 19:16:44 +01:00
Documentation fscrypt: allow 256-bit master keys with AES-256-XTS 2021-11-18 19:16:11 +01:00
drivers drm/ttm: remove ttm_bo_vm_insert_huge() 2021-11-18 19:17:08 +01:00
fs io-wq: fix max-workers not correctly set on multi-node system 2021-11-18 19:17:05 +01:00
include drm/ttm: remove ttm_bo_vm_insert_huge() 2021-11-18 19:17:08 +01:00
init bootconfig: init: Fix memblock leak in xbc_make_cmdline() 2021-10-10 22:27:40 -04:00
ipc ipc: remove memcg accounting for sops objects in do_semtimedop() 2021-09-14 10:22:11 -07:00
kernel kdb: Adopt scheduler's task classification 2021-11-18 19:17:06 +01:00
lib dyndbg: make dyndbg a known cli param 2021-11-18 19:16:52 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm kfence: always use static branches to guard kfence_alloc() 2021-11-12 15:05:49 +01:00
net net: dsa: felix: fix broken VLAN-tagged PTP under VLAN-aware bridge 2021-11-18 19:17:06 +01:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-18 19:16:42 +01:00
scripts leaking_addresses: Always print a trailing newline 2021-11-18 19:16:16 +01:00
security apparmor: fix error check 2021-11-18 19:16:58 +01:00
sound ASoC: rsnd: Fix an error handling path in 'rsnd_node_count()' 2021-11-18 19:16:57 +01:00
tools selftests: net: properly support IPv6 in GSO GRE test 2021-11-18 19:17:07 +01:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Remove tlbs_dirty 2021-09-23 11:01:12 -04:00
.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 Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 drm fixes for 5.15 final 2021-10-28 12:17:01 -07:00
Makefile Linux 5.15.2 2021-11-12 15:05:52 +01:00
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.