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Filename Latest commit message Latest commit date
Jann Horn b2fdd7f1b6 x86/mm: Disable hugetlb page table sharing on 32-bit
commit 76303ee8d54bff6d9a6d55997acd88a6c2ba63cf upstream.

Only select ARCH_WANT_HUGE_PMD_SHARE on 64-bit x86.
Page table sharing requires at least three levels because it involves
shared references to PMD tables; 32-bit x86 has either two-level paging
(without PAE) or three-level paging (with PAE), but even with
three-level paging, having a dedicated PGD entry for hugetlb is only
barely possible (because the PGD only has four entries), and it seems
unlikely anyone's actually using PMD sharing on 32-bit.

Having ARCH_WANT_HUGE_PMD_SHARE enabled on non-PAE 32-bit X86 (which
has 2-level paging) became particularly problematic after commit
59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count"),
since that changes `struct ptdesc` such that the `pt_mm` (for PGDs) and
the `pt_share_count` (for PMDs) share the same union storage - and with
2-level paging, PMDs are PGDs.

(For comparison, arm64 also gates ARCH_WANT_HUGE_PMD_SHARE on the
configuration of page tables such that it is never enabled with 2-level
paging.)

Closes: https://lore.kernel.org/r/srhpjxlqfna67blvma5frmy3aa@altlinux.org
Fixes: cfe28c5d63 ("x86: mm: Remove x86 version of huge_pmd_share.")
Reported-by: Vitaly Chikunov <vt@altlinux.org>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Vitaly Chikunov <vt@altlinux.org>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250702-x86-2level-hugetlb-v2-1-1a98096edf92%40google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-07-17 18:25:06 +02:00
arch x86/mm: Disable hugetlb page table sharing on 32-bit 2025-07-17 18:25:06 +02:00
block block: fix 'kmem_cache of name 'bio-108' already exists' 2025-04-10 14:29:37 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:11:22 +02:00
crypto crypto: algif_hash - fix double free in hash_accept 2025-06-04 14:32:35 +02:00
Documentation scsi: ufs: core: Fix spelling of a sysfs attribute name 2025-07-17 18:24:58 +02:00
drivers Input: atkbd - do not skip atkbd_deactivate() when skipping ATKBD_CMD_GETID 2025-07-17 18:25:06 +02:00
fs NFSv4/flexfiles: Fix handling of NFS level errors in I/O 2025-07-17 18:25:04 +02:00
include drm/sched: Increment job count before swapping tail spsc queue 2025-07-17 18:25:03 +02:00
init bpfilter: match bit size of bpfilter_umh to that of the kernel 2025-07-17 18:24:51 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:02:52 +01:00
kernel perf: Fix sample vs do_exit() 2025-06-27 11:02:58 +01:00
lib lib: test_objagg: Set error message in check_expect_hints_stats() 2025-07-17 18:24:56 +02:00
LICENSES
mm mm/huge_memory: fix dereferencing invalid pmd migration entry 2025-06-27 11:02:58 +01:00
net net: appletalk: Fix device refcount leak in atrtr_create() 2025-07-17 18:25:04 +02:00
samples samples/bpf: Fix a resource leak 2024-12-14 19:44:50 +01:00
scripts kbuild: use -MMD instead of -MD to exclude system headers from dependency 2025-07-17 18:24:51 +02:00
security selinux: fix selinux_xfrm_alloc_user() to set correct ctx_len 2025-06-27 11:02:56 +01:00
sound ALSA: sb: Force to disable DMAs once when DMA mode is changed 2025-07-17 18:24:57 +02:00
tools perf record: Fix incorrect --user-regs comments 2025-06-27 11:02:48 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-07-17 18:24:51 +02:00
virt KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status 2024-12-19 18:05:04 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-11-08 16:20:33 +01:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS platform: Add Surface platform directory 2025-06-27 11:02:56 +01:00
Makefile Linux 5.4.295 2025-06-27 11:02:58 +01:00
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.