linux-stable.git/Documentation/admin-guide/kernel-parameters.txt, branch linux-6.10.y

proc: add config & param to block forcing mem writes

2024-10-10T10:00:20+00:00

[ Upstream commit 41e8149c8892ed1962bd15350b3c3e6e90cba7f4 ]

This adds a Kconfig option and boot param to allow removing
the FOLL_FORCE flag from /proc/pid/mem write calls because
it can be abused.

The traditional forcing behavior is kept as default because
it can break GDB and some other use cases.

Previously we tried a more sophisticated approach allowing
distributions to fine-tune /proc/pid/mem behavior, however
that got NAK-ed by Linus [1], who prefers this simpler
approach with semantics also easier to understand for users.

Link: https://lore.kernel.org/lkml/CAHk-=wiGWLChxYmUA5HrT5aopZrB7_2VTa0NLZcxORgkUe5tEQ@mail.gmail.com/ [1]
Cc: Doug Anderson 
Cc: Jeff Xu 
Cc: Jann Horn 
Cc: Kees Cook 
Cc: Ard Biesheuvel 
Cc: Christian Brauner 
Suggested-by: Linus Torvalds 
Signed-off-by: Linus Torvalds 
Signed-off-by: Adrian Ratiu 
Link: https://lore.kernel.org/r/20240802080225.89408-1-adrian.ratiu@collabora.com
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

profiling: remove profile=sleep support

2024-08-14T13:34:17+00:00

commit b88f55389ad27f05ed84af9e1026aa64dbfabc9a upstream.

The kernel sleep profile is no longer working due to a recursive locking
bug introduced by commit 42a20f86dc19 ("sched: Add wrapper for get_wchan()
to keep task blocked")

Booting with the 'profile=sleep' kernel command line option added or
executing

  # echo -n sleep > /sys/kernel/profiling

after boot causes the system to lock up.

Lockdep reports

  kthreadd/3 is trying to acquire lock:
  ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: get_wchan+0x32/0x70

  but task is already holding lock:
  ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: try_to_wake_up+0x53/0x370

with the call trace being

   lock_acquire+0xc8/0x2f0
   get_wchan+0x32/0x70
   __update_stats_enqueue_sleeper+0x151/0x430
   enqueue_entity+0x4b0/0x520
   enqueue_task_fair+0x92/0x6b0
   ttwu_do_activate+0x73/0x140
   try_to_wake_up+0x213/0x370
   swake_up_locked+0x20/0x50
   complete+0x2f/0x40
   kthread+0xfb/0x180

However, since nobody noticed this regression for more than two years,
let's remove 'profile=sleep' support based on the assumption that nobody
needs this functionality.

Fixes: 42a20f86dc19 ("sched: Add wrapper for get_wchan() to keep task blocked")
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Tetsuo Handa 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sched/core: Drop spinlocks on contention iff kernel is preemptible

2024-08-03T06:59:36+00:00

[ Upstream commit c793a62823d1ce8f70d9cfc7803e3ea436277cda ]

Use preempt_model_preemptible() to detect a preemptible kernel when
deciding whether or not to reschedule in order to drop a contended
spinlock or rwlock.  Because PREEMPT_DYNAMIC selects PREEMPTION, kernels
built with PREEMPT_DYNAMIC=y will yield contended locks even if the live
preemption model is "none" or "voluntary".  In short, make kernels with
dynamically selected models behave the same as kernels with statically
selected models.

Somewhat counter-intuitively, NOT yielding a lock can provide better
latency for the relevant tasks/processes.  E.g. KVM x86's mmu_lock, a
rwlock, is often contended between an invalidation event (takes mmu_lock
for write) and a vCPU servicing a guest page fault (takes mmu_lock for
read).  For _some_ setups, letting the invalidation task complete even
if there is mmu_lock contention provides lower latency for *all* tasks,
i.e. the invalidation completes sooner *and* the vCPU services the guest
page fault sooner.

But even KVM's mmu_lock behavior isn't uniform, e.g. the "best" behavior
can vary depending on the host VMM, the guest workload, the number of
vCPUs, the number of pCPUs in the host, why there is lock contention, etc.

In other words, simply deleting the CONFIG_PREEMPTION guard (or doing the
opposite and removing contention yielding entirely) needs to come with a
big pile of data proving that changing the status quo is a net positive.

Opportunistically document this side effect of preempt=full, as yielding
contended spinlocks can have significant, user-visible impact.

Fixes: c597bfddc9e9 ("sched: Provide Kconfig support for default dynamic preempt mode")
Signed-off-by: Sean Christopherson 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Ankur Arora 
Reviewed-by: Chen Yu 
Link: https://lore.kernel.org/kvm/ef81ff36-64bb-4cfe-ae9b-e3acf47bff24@proxmox.com
Signed-off-by: Sasha Levin

Merge tag 'tty-6.10-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2024-06-30T15:57:43+00:00

Pull tty / serial / console fixes from Greg KH:
 "Here are a bunch of fixes/reverts for 6.10-rc6.  Include in here are:

   - revert the bunch of tty/serial/console changes that landed in -rc1
     that didn't quite work properly yet.

     Everyone agreed to just revert them for now and will work on making
     them better for a future release instead of trying to quick fix the
     existing changes this late in the release cycle

   - 8250 driver port count bugfix

   - Other tiny serial port bugfixes for reported issues

  All of these have been in linux-next this week with no reported
  issues"

* tag 'tty-6.10-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  Revert "printk: Save console options for add_preferred_console_match()"
  Revert "printk: Don't try to parse DEVNAME:0.0 console options"
  Revert "printk: Flag register_console() if console is set on command line"
  Revert "serial: core: Add support for DEVNAME:0.0 style naming for kernel console"
  Revert "serial: core: Handle serial console options"
  Revert "serial: 8250: Add preferred console in serial8250_isa_init_ports()"
  Revert "Documentation: kernel-parameters: Add DEVNAME:0.0 format for serial ports"
  Revert "serial: 8250: Fix add preferred console for serial8250_isa_init_ports()"
  Revert "serial: core: Fix ifdef for serial base console functions"
  serial: bcm63xx-uart: fix tx after conversion to uart_port_tx_limited()
  serial: core: introduce uart_port_tx_limited_flags()
  Revert "serial: core: only stop transmit when HW fifo is empty"
  serial: imx: set receiver level before starting uart
  tty: mcf: MCF54418 has 10 UARTS
  serial: 8250_omap: Implementation of Errata i2310
  tty: serial: 8250: Fix port count mismatch with the device

Revert "Documentation: kernel-parameters: Add DEVNAME:0.0 format for serial ports"

2024-06-25T05:57:51+00:00

This reverts commit 5c3a766e9f057ee7a54b5d7addff7fab02676fea.

Let's roll back all of the serial core and printk console changes that
went into 6.10-rc1 as there still are problems with them that need to be
sorted out.

Link: https://lore.kernel.org/r/ZnpRozsdw6zbjqze@tlindgre-MOBL1
Reported-by: Petr Mladek 
Reported-by: Tony Lindgren 
Cc: Jiri Slaby 
Cc: John Ogness 
Cc: Sergey Senozhatsky 
Cc: Andy Shevchenko 
Cc: Ilpo Järvinen 
Signed-off-by: Greg Kroah-Hartman

Revert "mm: init_mlocked_on_free_v3"

2024-06-15T17:43:05+00:00

There was insufficient review and no agreement that this is the right
approach.

There are serious flaws with the implementation that make processes using
mlock() not even work with simple fork() [1] and we get reliable crashes
when rebooting.

Further, simply because we might be unmapping a single PTE of a large
mlocked folio, we shouldn't zero out the whole folio.

... especially because the code can also *corrupt* urelated memory because
	kernel_init_pages(page, folio_nr_pages(folio));

Could end up writing outside of the actual folio if we work with a tail
page.

Let's revert it.  Once there is agreement that this is the right approach,
the issues were fixed and there was reasonable review and proper testing,
we can consider it again.

[1] https://lkml.kernel.org/r/4da9da2f-73e4-45fd-b62f-a8a513314057@redhat.com

Link: https://lkml.kernel.org/r/20240605091710.38961-1-david@redhat.com
Fixes: ba42b524a040 ("mm: init_mlocked_on_free_v3")
Signed-off-by: David Hildenbrand 
Reported-by: David Wang <00107082@163.com>
Closes: https://lore.kernel.org/lkml/20240528151340.4282-1-00107082@163.com/
Reported-by: Lance Yang 
Closes: https://lkml.kernel.org/r/20240601140917.43562-1-ioworker0@gmail.com
Acked-by: Lance Yang 
Cc: York Jasper Niebuhr 
Cc: Matthew Wilcox (Oracle) 
Cc: Kees Cook 
Signed-off-by: Andrew Morton

platform/x86: touchscreen_dmi: Add support for setting touchscreen properties from cmdline

2024-05-27T09:42:57+00:00

On x86/ACPI platforms touchscreens mostly just work without needing any
device/model specific configuration. But in some cases (mostly with Silead
and Goodix touchscreens) it is still necessary to manually specify various
touchscreen-properties on a per model basis.

touchscreen_dmi is a special place for DMI quirks for this, but it can be
challenging for users to figure out the right property values, especially
for Silead touchscreens where non of these can be read back from
the touchscreen-controller.

ATM users can only test touchscreen properties by editing touchscreen_dmi.c
and then building a completely new kernel which makes it unnecessary
difficult for users to test and submit properties when necessary for their
laptop / tablet model.

Add support for specifying properties on the kernel commandline to allow
users to easily figure out the right settings. See the added documentation
in kernel-parameters.txt for the commandline syntax.

Cc: Gregor Riepl 
Signed-off-by: Hans de Goede 
Link: https://lore.kernel.org/r/20240523143601.47555-1-hdegoede@redhat.com

Merge tag 'tty-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2024-05-22T18:53:02+00:00

Pull tty / serial updates from Greg KH:
 "Here is the big set of tty/serial driver changes for 6.10-rc1.
  Included in here are:

   - Usual good set of api cleanups and evolution by Jiri Slaby to make
     the serial interfaces move out of the 1990's by using kfifos
     instead of hand-rolling their own logic.

   - 8250_exar driver updates

   - max3100 driver updates

   - sc16is7xx driver updates

   - exar driver updates

   - sh-sci driver updates

   - tty ldisc api addition to help refuse bindings

   - other smaller serial driver updates

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'tty-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (113 commits)
  serial: Clear UPF_DEAD before calling tty_port_register_device_attr_serdev()
  serial: imx: Raise TX trigger level to 8
  serial: 8250_pnp: Simplify "line" related code
  serial: sh-sci: simplify locking when re-issuing RXDMA fails
  serial: sh-sci: let timeout timer only run when DMA is scheduled
  serial: sh-sci: describe locking requirements for invalidating RXDMA
  serial: sh-sci: protect invalidating RXDMA on shutdown
  tty: add the option to have a tty reject a new ldisc
  serial: core: Call device_set_awake_path() for console port
  dt-bindings: serial: brcm,bcm2835-aux-uart: convert to dtschema
  tty: serial: uartps: Add support for uartps controller reset
  arm64: zynqmp: Add resets property for UART nodes
  dt-bindings: serial: cdns,uart: Add optional reset property
  serial: 8250_pnp: Switch to DEFINE_SIMPLE_DEV_PM_OPS()
  serial: 8250_exar: Keep the includes sorted
  serial: 8250_exar: Make type of bit the same in exar_ee_*_bit()
  serial: 8250_exar: Use BIT() in exar_ee_read()
  serial: 8250_exar: Switch to use dev_err_probe()
  serial: 8250_exar: Return directly from switch-cases
  serial: 8250_exar: Decrease indentation level
  ...

Merge tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-05-19T21:02:03+00:00

Pull non-mm updates from Andrew Morton:
 "Mainly singleton patches, documented in their respective changelogs.
  Notable series include:

   - Some maintenance and performance work for ocfs2 in Heming Zhao's
     series "improve write IO performance when fragmentation is high".

   - Some ocfs2 bugfixes from Su Yue in the series "ocfs2 bugs fixes
     exposed by fstests".

   - kfifo header rework from Andy Shevchenko in the series "kfifo:
     Clean up kfifo.h".

   - GDB script fixes from Florian Rommel in the series "scripts/gdb:
     Fixes for $lx_current and $lx_per_cpu".

   - After much discussion, a coding-style update from Barry Song
     explaining one reason why inline functions are preferred over
     macros. The series is "codingstyle: avoid unused parameters for a
     function-like macro""

* tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (62 commits)
  fs/proc: fix softlockup in __read_vmcore
  nilfs2: convert BUG_ON() in nilfs_finish_roll_forward() to WARN_ON()
  scripts: checkpatch: check unused parameters for function-like macro
  Documentation: coding-style: ask function-like macros to evaluate parameters
  nilfs2: use __field_struct() for a bitwise field
  selftests/kcmp: remove unused open mode
  nilfs2: remove calls to folio_set_error() and folio_clear_error()
  kernel/watchdog_perf.c: tidy up kerneldoc
  watchdog: allow nmi watchdog to use raw perf event
  watchdog: handle comma separated nmi_watchdog command line
  nilfs2: make superblock data array index computation sparse friendly
  squashfs: remove calls to set the folio error flag
  squashfs: convert squashfs_symlink_read_folio to use folio APIs
  scripts/gdb: fix detection of current CPU in KGDB
  scripts/gdb: make get_thread_info accept pointers
  scripts/gdb: fix parameter handling in $lx_per_cpu
  scripts/gdb: fix failing KGDB detection during probe
  kfifo: don't use "proxy" headers
  media: stih-cec: add missing io.h
  media: rc: add missing io.h
  ...

Merge tag 'mm-stable-2024-05-17-19-19' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-05-19T16:21:03+00:00

Pull mm updates from Andrew Morton:
"The usual shower of singleton fixes and minor series all over MM,
documented (hopefully adequately) in the respective changelogs.
Notable series include:

- Lucas Stach has provided some page-mapping cleanup/consolidation/
maintainability work in the series "mm/treewide: Remove pXd_huge()
API".

- In the series "Allow migrate on protnone reference with
MPOL_PREFERRED_MANY policy", Donet Tom has optimized mempolicy's
MPOL_PREFERRED_MANY mode, yielding almost doubled performance in
one test.

- In their series "Memory allocation profiling" Kent Overstreet and
Suren Baghdasaryan have contributed a means of determining (via
/proc/allocinfo) whereabouts in the kernel memory is being
allocated: number of calls and amount of memory.

- Matthew Wilcox has provided the series "Various significant MM
patches" which does a number of rather unrelated things, but in
largely similar code sites.

- In his series "mm: page_alloc: freelist migratetype hygiene"
Johannes Weiner has fixed the page allocator's handling of
migratetype requests, with resulting improvements in compaction
efficiency.

- In the series "make the hugetlb migration strategy consistent"
Baolin Wang has fixed a hugetlb migration issue, which should
improve hugetlb allocation reliability.

- Liu Shixin has hit an I/O meltdown caused by readahead in a
memory-tight memcg. Addressed in the series "Fix I/O high when
memory almost met memcg limit".

- In the series "mm/filemap: optimize folio adding and splitting"
Kairui Song has optimized pagecache insertion, yielding ~10%
performance improvement in one test.

- Baoquan He has cleaned up and consolidated the early zone
initialization code in the series "mm/mm_init.c: refactor
free_area_init_core()".

- Baoquan has also redone some MM initializatio code in the series
"mm/init: minor clean up and improvement".

- MM helper cleanups from Christoph Hellwig in his series "remove
follow_pfn".

- More cleanups from Matthew Wilcox in the series "Various
page->flags cleanups".

- Vlastimil Babka has contributed maintainability improvements in the
series "memcg_kmem hooks refactoring".

- More folio conversions and cleanups in Matthew Wilcox's series:
"Convert huge_zero_page to huge_zero_folio"
"khugepaged folio conversions"
"Remove page_idle and page_young wrappers"
"Use folio APIs in procfs"
"Clean up __folio_put()"
"Some cleanups for memory-failure"
"Remove page_mapping()"
"More folio compat code removal"

- David Hildenbrand chipped in with "fs/proc/task_mmu: convert
hugetlb functions to work on folis".

- Code consolidation and cleanup work related to GUP's handling of
hugetlbs in Peter Xu's series "mm/gup: Unify hugetlb, part 2".

- Rick Edgecombe has developed some fixes to stack guard gaps in the
series "Cover a guard gap corner case".

- Jinjiang Tu has fixed KSM's behaviour after a fork+exec in the
series "mm/ksm: fix ksm exec support for prctl".

- Baolin Wang has implemented NUMA balancing for multi-size THPs.
This is a simple first-cut implementation for now. The series is
"support multi-size THP numa balancing".

- Cleanups to vma handling helper functions from Matthew Wilcox in
the series "Unify vma_address and vma_pgoff_address".

- Some selftests maintenance work from Dev Jain in the series
"selftests/mm: mremap_test: Optimizations and style fixes".

- Improvements to the swapping of multi-size THPs from Ryan Roberts
in the series "Swap-out mTHP without splitting".

- Kefeng Wang has significantly optimized the handling of arm64's
permission page faults in the series
"arch/mm/fault: accelerate pagefault when badaccess"
"mm: remove arch's private VM_FAULT_BADMAP/BADACCESS"

- GUP cleanups from David Hildenbrand in "mm/gup: consistently call
it GUP-fast".

- hugetlb fault code cleanups from Vishal Moola in "Hugetlb fault
path to use struct vm_fault".

- selftests build fixes from John Hubbard in the series "Fix
selftests/mm build without requiring "make headers"".

- Memory tiering fixes/improvements from Ho-Ren (Jack) Chuang in the
series "Improved Memory Tier Creation for CPUless NUMA Nodes".
Fixes the initialization code so that migration between different
memory types works as intended.

- David Hildenbrand has improved follow_pte() and fixed an errant
driver in the series "mm: follow_pte() improvements and acrn
follow_pte() fixes".

- David also did some cleanup work on large folio mapcounts in his
series "mm: mapcount for large folios + page_mapcount() cleanups".

- Folio conversions in KSM in Alex Shi's series "transfer page to
folio in KSM".

- Barry Song has added some sysfs stats for monitoring multi-size
THP's in the series "mm: add per-order mTHP alloc and swpout
counters".

- Some zswap cleanups from Yosry Ahmed in the series "zswap
same-filled and limit checking cleanups".

- Matthew Wilcox has been looking at buffer_head code and found the
documentation to be lacking. The series is "Improve buffer head
documentation".

- Multi-size THPs get more work, this time from Lance Yang. His
series "mm/madvise: enhance lazyfreeing with mTHP in madvise_free"
optimizes the freeing of these things.

- Kemeng Shi has added more userspace-visible writeback
instrumentation in the series "Improve visibility of writeback".

- Kemeng Shi then sent some maintenance work on top in the series
"Fix and cleanups to page-writeback".

- Matthew Wilcox reduces mmap_lock traffic in the anon vma code in
the series "Improve anon_vma scalability for anon VMAs". Intel's
test bot reported an improbable 3x improvement in one test.

- SeongJae Park adds some DAMON feature work in the series
"mm/damon: add a DAMOS filter type for page granularity access recheck"
"selftests/damon: add DAMOS quota goal test"

- Also some maintenance work in the series
"mm/damon/paddr: simplify page level access re-check for pageout"
"mm/damon: misc fixes and improvements"

- David Hildenbrand has disabled some known-to-fail selftests ni the
series "selftests: mm: cow: flag vmsplice() hugetlb tests as
XFAIL".

- memcg metadata storage optimizations from Shakeel Butt in "memcg:
reduce memory consumption by memcg stats".

- DAX fixes and maintenance work from Vishal Verma in the series
"dax/bus.c: Fixups for dax-bus locking""

* tag 'mm-stable-2024-05-17-19-19' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (426 commits)
memcg, oom: cleanup unused memcg_oom_gfp_mask and memcg_oom_order
selftests/mm: hugetlb_madv_vs_map: avoid test skipping by querying hugepage size at runtime
mm/hugetlb: add missing VM_FAULT_SET_HINDEX in hugetlb_wp
mm/hugetlb: add missing VM_FAULT_SET_HINDEX in hugetlb_fault
selftests: cgroup: add tests to verify the zswap writeback path
mm: memcg: make alloc_mem_cgroup_per_node_info() return bool
mm/damon/core: fix return value from damos_wmark_metric_value
mm: do not update memcg stats for NR_{FILE/SHMEM}_PMDMAPPED
selftests: cgroup: remove redundant enabling of memory controller
Docs/mm/damon/maintainer-profile: allow posting patches based on damon/next tree
Docs/mm/damon/maintainer-profile: change the maintainer's timezone from PST to PT
Docs/mm/damon/design: use a list for supported filters
Docs/admin-guide/mm/damon/usage: fix wrong schemes effective quota update command
Docs/admin-guide/mm/damon/usage: fix wrong example of DAMOS filter matching sysfs file
selftests/damon: classify tests for functionalities and regressions
selftests/damon/_damon_sysfs: use 'is' instead of '==' for 'None'
selftests/damon/_damon_sysfs: find sysfs mount point from /proc/mounts
selftests/damon/_damon_sysfs: check errors from nr_schemes file reads
mm/damon/core: initialize ->esz_bp from damos_quota_init_priv()
selftests/damon: add a test for DAMOS quota goal
...