Skip to content

L
linux
Switch branch/tag
  1. 12 Apr, 2023 10 commits
  3. 09 Mar, 2023 3 commits
  5. 08 Mar, 2023 3 commits
    • Linus Torvalds's avatar
      Merge tag 'fs_for_v6.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs · 6a98c9ca
      Linus Torvalds authored 
      Pull udf fixes from Jan Kara:
 "Fix bugs in UDF caused by the big pile of changes that went in during
  the merge window"

* tag 'fs_for_v6.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  udf: Warn if block mapping is done for in-ICB files
  udf: Fix reading of in-ICB files
  udf: Fix lost writes in udf_adinicb_writepage()
      6a98c9ca
    • Linus Torvalds's avatar
      Merge tag 'platform-drivers-x86-v6.3-2' of... · 55ee6646
      Linus Torvalds authored 
      Merge tag 'platform-drivers-x86-v6.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86

Pull x86 platform driver fixes from Hans de Goede:
 "A small set of assorted bug and build/warning fixes"

* tag 'platform-drivers-x86-v6.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86:
  platform: mellanox: mlx-platform: Initialize shift variable to 0
  platform/x86: int3472: Add GPIOs to Surface Go 3 Board data
  platform/x86: ISST: Fix kernel documentation warnings
  platform: x86: MLX_PLATFORM: select REGMAP instead of depending on it
  platform: mellanox: select REGMAP instead of depending on it
  platform/x86/intel/tpmi: Fix double free reported by Smatch
  platform/x86: ISST: Increase range of valid mail box commands
  platform/x86: dell-ddv: Fix temperature scaling
  platform/x86: dell-ddv: Fix cache invalidation on resume
  platform/x86/amd: pmc: remove CONFIG_SUSPEND checks
      55ee6646
    • Linus Torvalds's avatar
      x86/resctl: fix scheduler confusion with 'current' · 7fef0997
      Linus Torvalds authored 
      The implementation of 'current' on x86 is very intentionally special: it
is a very common thing to look up, and it uses 'this_cpu_read_stable()'
to get the current thread pointer efficiently from per-cpu storage.

And the keyword in there is 'stable': the current thread pointer never
changes as far as a single thread is concerned.  Even if when a thread
is preempted, or moved to another CPU, or even across an explicit call
'schedule()' that thread will still have the same value for 'current'.

It is, after all, the kernel base pointer to thread-local storage.
That's why it's stable to begin with, but it's also why it's important
enough that we have that special 'this_cpu_read_stable()' access for it.

So this is all done very intentionally to allow the compiler to treat
'current' as a value that never visibly changes, so that the compiler
can do CSE and combine multiple different 'current' accesses into one.

However, there is obviously one very special situation when the
currently running thread does actually change: inside the scheduler
itself.

So the scheduler code paths are special, and do not have a 'current'
thread at all.  Instead there are _two_ threads: the previous and the
next thread - typically called 'prev' and 'next' (or prev_p/next_p)
internally.

So this is all actually quite straightforward and simple, and not all
that complicated.

Except for when you then have special code that is run in scheduler
context, that code then has to be aware that 'current' isn't really a
valid thing.  Did you mean 'prev'? Did you mean 'next'?

In fact, even if then look at the code, and you use 'current' after the
new value has been assigned to the percpu variable, we have explicitly
told the compiler that 'current' is magical and always stable.  So the
compiler is quite free to use an older (or newer) value of 'current',
and the actual assignment to the percpu storage is not relevant even if
it might look that way.

Which is exactly what happened in the resctl code, that blithely used
'current' in '__resctrl_sched_in()' when it really wanted the new
process state (as implied by the name: we're scheduling 'into' that new
resctl state).  And clang would end up just using the old thread pointer
value at least in some configurations.

This could have happened with gcc too, and purely depends on random
compiler details.  Clang just seems to have been more aggressive about
moving the read of the per-cpu current_task pointer around.

The fix is trivial: just make the resctl code adhere to the scheduler
rules of using the prev/next thread pointer explicitly, instead of using
'current' in a situation where it just wasn't valid.

That same code is then also used outside of the scheduler context (when
a thread resctl state is explicitly changed), and then we will just pass
in 'current' as that pointer, of course.  There is no ambiguity in that
case.

The fix may be trivial, but noticing and figuring out what went wrong
was not.  The credit for that goes to Stephane Eranian.
Reported-by: default avatarStephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/lkml/20230303231133.1486085-1-eranian@google.com/
Link: https://lore.kernel.org/lkml/alpine.LFD.2.01.0908011214330.3304@localhost.localdomain/Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Tested-by: default avatarTony Luck <tony.luck@intel.com>
Tested-by: default avatarStephane Eranian <eranian@google.com>
Tested-by: default avatarBabu Moger <babu.moger@amd.com>
Cc: stable@kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7fef0997
  7. 07 Mar, 2023 11 commits
  9. 06 Mar, 2023 8 commits
  11. 05 Mar, 2023 5 commits
    • Linus Torvalds's avatar
      Linux 6.3-rc1 · fe15c26e
      Linus Torvalds authored
      fe15c26e
    • Linus Torvalds's avatar
      cpumask: re-introduce constant-sized cpumask optimizations · 596ff4a0
      Linus Torvalds authored 
      Commit aa47a7c2 ("lib/cpumask: deprecate nr_cpumask_bits") resulted
in the cpumask operations potentially becoming hugely less efficient,
because suddenly the cpumask was always considered to be variable-sized.

The optimization was then later added back in a limited form by commit
6f9c07be ("lib/cpumask: add FORCE_NR_CPUS config option"), but that
FORCE_NR_CPUS option is not useful in a generic kernel and more of a
special case for embedded situations with fixed hardware.

Instead, just re-introduce the optimization, with some changes.

Instead of depending on CPUMASK_OFFSTACK being false, and then always
using the full constant cpumask width, this introduces three different
cpumask "sizes":

 - the exact size (nr_cpumask_bits) remains identical to nr_cpu_ids.

   This is used for situations where we should use the exact size.

 - the "small" size (small_cpumask_bits) is the NR_CPUS constant if it
   fits in a single word and the bitmap operations thus end up able
   to trigger the "small_const_nbits()" optimizations.

   This is used for the operations that have optimized single-word
   cases that get inlined, notably the bit find and scanning functions.

 - the "large" size (large_cpumask_bits) is the NR_CPUS constant if it
   is an sufficiently small constant that makes simple "copy" and
   "clear" operations more efficient.

   This is arbitrarily set at four words or less.

As a an example of this situation, without this fixed size optimization,
cpumask_clear() will generate code like

        movl    nr_cpu_ids(%rip), %edx
        addq    $63, %rdx
        shrq    $3, %rdx
        andl    $-8, %edx
        callq   memset@PLT

on x86-64, because it would calculate the "exact" number of longwords
that need to be cleared.

In contrast, with this patch, using a MAX_CPU of 64 (which is quite a
reasonable value to use), the above becomes a single

	movq $0,cpumask

instruction instead, because instead of caring to figure out exactly how
many CPU's the system has, it just knows that the cpumask will be a
single word and can just clear it all.

Note that this does end up tightening the rules a bit from the original
version in another way: operations that set bits in the cpumask are now
limited to the actual nr_cpu_ids limit, whereas we used to do the
nr_cpumask_bits thing almost everywhere in the cpumask code.

But if you just clear bits, or scan for bits, we can use the simpler
compile-time constants.

In the process, remove 'cpumask_complement()' and 'for_each_cpu_not()'
which were not useful, and which fundamentally have to be limited to
'nr_cpu_ids'.  Better remove them now than have somebody introduce use
of them later.

Of course, on x86-64 with MAXSMP there is no sane small compile-time
constant for the cpumask sizes, and we end up using the actual CPU bits,
and will generate the above kind of horrors regardless.  Please don't
use MAXSMP unless you really expect to have machines with thousands of
cores.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      596ff4a0
    • Linus Torvalds's avatar
      Merge tag 'v6.3-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 · f915322f
      Linus Torvalds authored 
      Pull crypto fix from Herbert Xu:
 "Fix a regression in the caam driver"

* tag 'v6.3-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: caam - Fix edesc/iv ordering mixup
      f915322f
    • Linus Torvalds's avatar
      Merge tag 'x86-urgent-2023-03-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 7f9ec7d8
      Linus Torvalds authored 
      Pull x86 updates from Thomas Gleixner:
 "A small set of updates for x86:

   - Return -EIO instead of success when the certificate buffer for SEV
     guests is not large enough

   - Allow STIPB to be enabled with legacy IBSR. Legacy IBRS is cleared
     on return to userspace for performance reasons, but the leaves user
     space vulnerable to cross-thread attacks which STIBP prevents.
     Update the documentation accordingly"

* tag 'x86-urgent-2023-03-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  virt/sev-guest: Return -EIO if certificate buffer is not large enough
  Documentation/hw-vuln: Document the interaction between IBRS and STIBP
  x86/speculation: Allow enabling STIBP with legacy IBRS
      7f9ec7d8
    • Linus Torvalds's avatar
      Merge tag 'irq-urgent-2023-03-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 4e9c542c
      Linus Torvalds authored 
      Pull irq updates from Thomas Gleixner:
 "A set of updates for the interrupt susbsystem:

   - Prevent possible NULL pointer derefences in
     irq_data_get_affinity_mask() and irq_domain_create_hierarchy()

   - Take the per device MSI lock before invoking code which relies on
     it being hold

   - Make sure that MSI descriptors are unreferenced before freeing
     them. This was overlooked when the platform MSI code was converted
     to use core infrastructure and results in a fals positive warning

   - Remove dead code in the MSI subsystem

   - Clarify the documentation for pci_msix_free_irq()

   - More kobj_type constification"

* tag 'irq-urgent-2023-03-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  genirq/msi, platform-msi: Ensure that MSI descriptors are unreferenced
  genirq/msi: Drop dead domain name assignment
  irqdomain: Add missing NULL pointer check in irq_domain_create_hierarchy()
  genirq/irqdesc: Make kobj_type structures constant
  PCI/MSI: Clarify usage of pci_msix_free_irq()
  genirq/msi: Take the per-device MSI lock before validating the control structure
  genirq/ipi: Fix NULL pointer deref in irq_data_get_affinity_mask()
      4e9c542c
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7