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Mark Rutland 61d2d1808b arm64: mm: don't acquire mutex when rewriting swapper 
Since commit:

  47546a1912 ("arm64: mm: install KPTI nG mappings with MMU enabled)"

... when building with CONFIG_DEBUG_ATOMIC_SLEEP=y and booting under
QEMU TCG with '-cpu max', there's a boot-time splat:

| BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
| in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 15, name: migration/0
| preempt_count: 1, expected: 0
| RCU nest depth: 0, expected: 0
| no locks held by migration/0/15.
| irq event stamp: 28
| hardirqs last  enabled at (27): [<ffff8000091ed180>] _raw_spin_unlock_irq+0x3c/0x7c
| hardirqs last disabled at (28): [<ffff8000081b8d74>] multi_cpu_stop+0x150/0x18c
| softirqs last  enabled at (0): [<ffff80000809a314>] copy_process+0x594/0x1964
| softirqs last disabled at (0): [<0000000000000000>] 0x0
| CPU: 0 PID: 15 Comm: migration/0 Not tainted 6.0.0-rc3-00002-g419b42ff7eef #3
| Hardware name: linux,dummy-virt (DT)
| Stopper: multi_cpu_stop+0x0/0x18c <- stop_cpus.constprop.0+0xa0/0xfc
| Call trace:
|  dump_backtrace.part.0+0xd0/0xe0
|  show_stack+0x1c/0x5c
|  dump_stack_lvl+0x88/0xb4
|  dump_stack+0x1c/0x38
|  __might_resched+0x180/0x230
|  __might_sleep+0x4c/0xa0
|  __mutex_lock+0x5c/0x450
|  mutex_lock_nested+0x30/0x40
|  create_kpti_ng_temp_pgd+0x4fc/0x6d0
|  kpti_install_ng_mappings+0x2b8/0x3b0
|  cpu_enable_non_boot_scope_capabilities+0x7c/0xd0
|  multi_cpu_stop+0xa0/0x18c
|  cpu_stopper_thread+0x88/0x11c
|  smpboot_thread_fn+0x1ec/0x290
|  kthread+0x118/0x120
|  ret_from_fork+0x10/0x20

Since commit:

  ee017ee353 ("arm64/mm: avoid fixmap race condition when create pud mapping")

... once the kernel leave the SYSTEM_BOOTING state, the fixmap pagetable
entries are protected by the fixmap_lock mutex.

The new KPTI rewrite code uses __create_pgd_mapping() to create a
temporary pagetable. This happens in atomic context, after secondary
CPUs are brought up and the kernel has left the SYSTEM_BOOTING state.
Hence we try to acquire a mutex in atomic context, which is generally
unsound (though benign in this case as the mutex should be free and all
other CPUs are quiescent).

This patch avoids the issue by pulling the mutex out of alloc_init_pud()
and calling it at a higher level in the pagetable manipulation code.
This allows it to be used without locking where one CPU is known to be
in exclusive control of the machine, even after having left the
SYSTEM_BOOTING state.

Fixes: 47546a1912 ("arm64: mm: install KPTI nG mappings with MMU enabled")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220920134731.1625740-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
2022-09-22 12:55:39 +01:00
arch arm64: mm: don't acquire mutex when rewriting swapper 2022-09-22 12:55:39 +01:00
block block-6.0-2022-08-12 2022-08-13 13:37:36 -07:00
certs Kbuild updates for v5.20 2022-08-10 10:40:41 -07:00
crypto crypto: blake2b: effectively disable frame size warning 2022-08-10 17:59:11 -07:00
Documentation arm64: errata: add detection for AMEVCNTR01 incrementing incorrectly 2022-08-23 11:06:48 +01:00
drivers perf/arm_pmu_platform: fix tests for platform_get_irq() failure 2022-09-01 12:01:40 +01:00
fs take care to handle NULL ->proc_lseek() 2022-08-14 15:16:18 -04:00
include radix-tree: replace gfp.h inclusion with gfp_types.h 2022-08-14 13:31:03 -07:00
init arm64: fix rodata=full 2022-08-23 11:02:02 +01:00
io_uring io_uring-6.0-2022-08-13 2022-08-13 13:28:54 -07:00
ipc Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
kernel xen: branch for v6.0-rc1b 2022-08-14 09:28:54 -07:00
lib lib: remove lib/nodemask.c 2022-08-12 09:07:33 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm - hugetlb_vmemmap cleanups from Muchun Song 2022-08-10 11:18:00 -07:00
net Including fixes from bluetooth, bpf, can and netfilter. 2022-08-11 13:45:37 -07:00
samples Tracing updates for 5.20 / 6.0 2022-08-05 09:41:12 -07:00
scripts RISC-V Patches for the 5.20 Merge Window, Part 2 2022-08-12 18:39:43 -07:00
security + Features 2022-08-10 10:53:22 -07:00
sound sound fixes for 6.0-rc1 2022-08-12 09:55:32 -07:00
tools perf tools changes for v6.0: 2nd batch 2022-08-14 09:22:11 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Actually create debugfs in kvm_create_vm() 2022-08-10 15:08:28 -04:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.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 kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -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 xen: branch for v6.0-rc1b 2022-08-14 09:28:54 -07:00
Makefile Linux 6.0-rc1 2022-08-14 15:50:18 -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.