Expand the discussion of SRCU and its read-side critical sections in
the Linux Kernel Memory Model documentation file explanation.txt.  The
new material discusses recent changes to the memory model made in
commit 6cd244c87428 ("tools/memory-model: Provide exact SRCU
semantics").
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Jonas Oberhauser <jonas.oberhauser@huawei.com>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
CC: Will Deacon <will@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

As stated in the documentation and implied by its name, the ppo
(preserved program order) relation is intended to link po-earlier
to po-later instructions under certain conditions.  However, a
corner case currently allows instructions to be linked by ppo that
are not executed by the same thread, i.e., instructions are being
linked that have no po relation.

This happens due to the mb/strong-fence/fence relations, which (as
one case) provide order when locks are passed between threads
followed by an smp_mb__after_unlock_lock() fence.  This is
illustrated in the following litmus test (as can be seen when using
herd7 with `doshow ppo`):

P0(spinlock_t *x, spinlock_t *y)
{
    spin_lock(x);
    spin_unlock(x);
}

P1(spinlock_t *x, spinlock_t *y)
{
    spin_lock(x);
    smp_mb__after_unlock_lock();
    *y = 1;
}

The ppo relation will link P0's spin_lock(x) and P1's *y=1, because
P0 passes a lock to P1 which then uses this fence.

The patch makes ppo a subrelation of po by letting fence contribute
to ppo only in case the fence links events of the same thread.
Signed-off-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

LKMM has long provided only approximate handling of SRCU read-side
critical sections.  This has not been a pressing problem because LKMM's
traditional handling is correct for the common cases of non-overlapping
and properly nested critical sections.  However, LKMM's traditional
handling of partially overlapping critical sections incorrectly fuses
them into one large critical section.

For example, consider the following litmus test:

------------------------------------------------------------------------

C C-srcu-nest-5

(*
 * Result: Sometimes
 *
 * This demonstrates non-nested overlapping of SRCU read-side critical
 * sections.  Unlike RCU, SRCU critical sections do not unconditionally
 * nest.
 *)

{}

P0(int *x, int *y, struct srcu_struct *s1)
{
        int r1;
        int r2;
        int r3;
        int r4;

        r3 = srcu_read_lock(s1);
        r2 = READ_ONCE(*y);
        r4 = srcu_read_lock(s1);
        srcu_read_unlock(s1, r3);
        r1 = READ_ONCE(*x);
        srcu_read_unlock(s1, r4);
}

P1(int *x, int *y, struct srcu_struct *s1)
{
        WRITE_ONCE(*y, 1);
        synchronize_srcu(s1);
        WRITE_ONCE(*x, 1);
}

locations [0:r1]
exists (0:r1=1 /\ 0:r2=0)

------------------------------------------------------------------------

Current mainline incorrectly flattens the two critical sections into
one larger critical section, giving "Never" instead of the correct
"Sometimes":

------------------------------------------------------------------------

$ herd7 -conf linux-kernel.cfg C-srcu-nest-5.litmus
Test C-srcu-nest-5 Allowed
States 3
0:r1=0; 0:r2=0;
0:r1=0; 0:r2=1;
0:r1=1; 0:r2=1;
No
Witnesses
Positive: 0 Negative: 3
Flag srcu-bad-nesting
Condition exists (0:r1=1 /\ 0:r2=0)
Observation C-srcu-nest-5 Never 0 3
Time C-srcu-nest-5 0.01
Hash=e692c106cf3e84e20f12991dc438ff1b

------------------------------------------------------------------------

To its credit, it does complain about bad nesting.  But with this
commit we get the following result, which has the virtue of being
correct:

------------------------------------------------------------------------

$ herd7 -conf linux-kernel.cfg C-srcu-nest-5.litmus
Test C-srcu-nest-5 Allowed
States 4
0:r1=0; 0:r2=0;
0:r1=0; 0:r2=1;
0:r1=1; 0:r2=0;
0:r1=1; 0:r2=1;
Ok
Witnesses
Positive: 1 Negative: 3
Condition exists (0:r1=1 /\ 0:r2=0)
Observation C-srcu-nest-5 Sometimes 1 3
Time C-srcu-nest-5 0.05
Hash=e692c106cf3e84e20f12991dc438ff1b

------------------------------------------------------------------------

In addition, there are new srcu_down_read() and srcu_up_read()
functions on their way to mainline.  Roughly speaking, these are to
srcu_read_lock() and srcu_read_unlock() as down() and up() are to
mutex_lock() and mutex_unlock().  The key point is that
srcu_down_read() can execute in one process and the matching
srcu_up_read() in another, as shown in this litmus test:

------------------------------------------------------------------------

C C-srcu-nest-6

(*
 * Result: Never
 *
 * This would be valid for srcu_down_read() and srcu_up_read().
 *)

{}

P0(int *x, int *y, struct srcu_struct *s1, int *idx, int *f)
{
        int r2;
        int r3;

        r3 = srcu_down_read(s1);
        WRITE_ONCE(*idx, r3);
        r2 = READ_ONCE(*y);
        smp_store_release(f, 1);
}

P1(int *x, int *y, struct srcu_struct *s1, int *idx, int *f)
{
        int r1;
        int r3;
        int r4;

        r4 = smp_load_acquire(f);
        r1 = READ_ONCE(*x);
        r3 = READ_ONCE(*idx);
        srcu_up_read(s1, r3);
}

P2(int *x, int *y, struct srcu_struct *s1)
{
        WRITE_ONCE(*y, 1);
        synchronize_srcu(s1);
        WRITE_ONCE(*x, 1);
}

locations [0:r1]
filter (1:r4=1)
exists (1:r1=1 /\ 0:r2=0)

------------------------------------------------------------------------

When run on current mainline, this litmus test gets a complaint about
an unknown macro srcu_down_read().  With this commit:

------------------------------------------------------------------------

herd7 -conf linux-kernel.cfg C-srcu-nest-6.litmus
Test C-srcu-nest-6 Allowed
States 3
0:r1=0; 0:r2=0; 1:r1=0;
0:r1=0; 0:r2=1; 1:r1=0;
0:r1=0; 0:r2=1; 1:r1=1;
No
Witnesses
Positive: 0 Negative: 3
Condition exists (1:r1=1 /\ 0:r2=0)
Observation C-srcu-nest-6 Never 0 3
Time C-srcu-nest-6 0.02
Hash=c1f20257d052ca5e899be508bedcb2a1

------------------------------------------------------------------------

Note that the user must supply the flag "f" and the "filter" clause,
similar to what must be done to emulate call_rcu().

The commit works by treating srcu_read_lock()/srcu_down_read() as
loads and srcu_read_unlock()/srcu_up_read() as stores.  This allows us
to determine which unlock matches which lock by looking for a data
dependency between them.  In order for this to work properly, the data
dependencies have to be tracked through stores to intermediate
variables such as "idx" in the litmus test above; this is handled by
the new carry-srcu-data relation.  But it's important here (and in the
existing carry-dep relation) to avoid tracking the dependencies
through SRCU unlock stores.  Otherwise, in situations resembling:

	A: r1 = srcu_read_lock(s);
	B: srcu_read_unlock(s, r1);
	C: r2 = srcu_read_lock(s);
	D: srcu_read_unlock(s, r2);

it would look as if D was dependent on both A and C, because "s" would
appear to be an intermediate variable written by B and read by C.
This explains the complications in the definitions of carry-srcu-dep
and carry-dep.

As a debugging aid, the commit adds a check for errors in which the
value returned by one call to srcu_read_lock()/srcu_down_read() is
passed to more than one instance of srcu_read_unlock()/srcu_up_read().

Finally, since these SRCU-related primitives are now treated as
ordinary reads and writes, we have to add them into the lists of
marked accesses (i.e., not subject to data races) and lock-related
accesses (i.e., one shouldn't try to access an srcu_struct with a
non-lock-related primitive such as READ_ONCE() or a plain write).

Portions of this approach were suggested by Boqun Feng and Jonas
Oberhauser.

[ paulmck: Fix space-before-tab whitespace nit. ]
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

During a code-reading exercise of linux-kernel.cat CAT file, I generated
a graph to show the to-r relations. While likely not problematic for the
model, I found it confusing that a read-write address dependency would
show as a to-r edge on the graph.

This patch therefore restricts the to-r links derived from addr to only
read-read address dependencies, so that read-write address dependencies don't
show as to-r in the graphs. This should also prevent future users of to-r from
deriving incorrect relations. Note that a read-write address dep, obviously,
still ends up in the ppo relation via the to-w relation.

I verified that a read-read address dependency still shows up as a to-r
link in the graph, as it did before.

For reference, the problematic graph was generated with the following
command:
herd7 -conf linux-kernel.cfg \
   -doshow dep -doshow to-r -doshow to-w ./foo.litmus -show all -o OUT/
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit adds support for smp_mb__after_srcu_read_unlock(), which,
when combined with a prior srcu_read_unlock(), implies a full memory
barrier.  No ordering is guaranteed to accesses between the two, and
placing accesses between is bad practice in any case.

Tests may be found at https://github.com/paulmckrcu/litmus in files
matching manual/kernel/C-srcu-mb-*.litmus.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

LKMM uses two relations for talking about UNLOCK+LOCK pairings:

	1) po-unlock-lock-po, which handles UNLOCK+LOCK pairings
	   on the same CPU or immediate lock handovers on the same
	   lock variable

	2) po;[UL];(co|po);[LKW];po, which handles UNLOCK+LOCK pairs
	   literally as described in rcupdate.h#L1002, i.e., even
	   after a sequence of handovers on the same lock variable.

The latter relation is used only once, to provide the guarantee
defined in rcupdate.h#L1002 by smp_mb__after_unlock_lock(), which
makes any UNLOCK+LOCK pair followed by the fence behave like a full
barrier.

This patch drops this use in favor of using po-unlock-lock-po
everywhere, which unifies the way the model talks about UNLOCK+LOCK
pairings.  At first glance this seems to weaken the guarantee given
by LKMM: When considering a long sequence of lock handovers
such as below, where P0 hands the lock to P1, which hands it to P2,
which finally executes such an after_unlock_lock fence, the mb
relation currently links any stores in the critical section of P0
to instructions P2 executes after its fence, but not so after the
patch.

P0(int *x, int *y, spinlock_t *mylock)
{
        spin_lock(mylock);
        WRITE_ONCE(*x, 2);
        spin_unlock(mylock);
        WRITE_ONCE(*y, 1);
}

P1(int *y, int *z, spinlock_t *mylock)
{
        int r0 = READ_ONCE(*y); // reads 1
        spin_lock(mylock);
        spin_unlock(mylock);
        WRITE_ONCE(*z,1);
}

P2(int *z, int *d, spinlock_t *mylock)
{
        int r1 = READ_ONCE(*z); // reads 1
        spin_lock(mylock);
        spin_unlock(mylock);
        smp_mb__after_unlock_lock();
        WRITE_ONCE(*d,1);
}

P3(int *x, int *d)
{
        WRITE_ONCE(*d,2);
        smp_mb();
        WRITE_ONCE(*x,1);
}

exists (1:r0=1 /\ 2:r1=1 /\ x=2 /\ d=2)

Nevertheless, the ordering guarantee given in rcupdate.h is actually
not weakened.  This is because the unlock operations along the
sequence of handovers are A-cumulative fences.  They ensure that any
stores that propagate to the CPU performing the first unlock
operation in the sequence must also propagate to every CPU that
performs a subsequent lock operation in the sequence.  Therefore any
such stores will also be ordered correctly by the fence even if only
the final handover is considered a full barrier.

Indeed this patch does not affect the behaviors allowed by LKMM at
all.  The mb relation is used to define ordering through:
1) mb/.../ppo/hb, where the ordering is subsumed by hb+ where the
   lock-release, rfe, and unlock-acquire orderings each provide hb
2) mb/strong-fence/cumul-fence/prop, where the rfe and A-cumulative
   lock-release orderings simply add more fine-grained cumul-fence
   edges to substitute a single strong-fence edge provided by a long
   lock handover sequence
3) mb/strong-fence/pb and various similar uses in the definition of
   data races, where as discussed above any long handover sequence
   can be turned into a sequence of cumul-fence edges that provide
   the same ordering.
Signed-off-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Some of the warning labels used in the LKMM are unfortunately
ambiguous.  In particular, the same warning is used for both an
unmatched rcu_read_lock() call and for an unmatched rcu_read_unlock()
call.  Likewise for the srcu_* equivalents.  Also, the warning about
passing a wrong value to srcu_read_unlock() -- i.e., a value different
from the one returned by the matching srcu_read_lock() -- talks about
bad nesting rather than non-matching values.

Let's update the warning labels to make their meanings more clear.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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: Linus Torvalds <torvalds@linux-foundation.org>

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

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

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()

Pull vfs update from Al Viro:
 "Adding Christian Brauner as VFS co-maintainer"

* tag 'pull-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  Adding VFS co-maintainer

Pull VM_FAULT_RETRY fixes from Al Viro:
 "Some of the page fault handlers do not deal with the following case
  correctly:

   - handle_mm_fault() has returned VM_FAULT_RETRY

   - there is a pending fatal signal

   - fault had happened in kernel mode

  Correct action in such case is not "return unconditionally" - fatal
  signals are handled only upon return to userland and something like
  copy_to_user() would end up retrying the faulting instruction and
  triggering the same fault again and again.

  What we need to do in such case is to make the caller to treat that as
  failed uaccess attempt - handle exception if there is an exception
  handler for faulting instruction or oops if there isn't one.

  Over the years some architectures had been fixed and now are handling
  that case properly; some still do not. This series should fix the
  remaining ones.

  Status:

   - m68k, riscv, hexagon, parisc: tested/acked by maintainers.

   - alpha, sparc32, sparc64: tested locally - bug has been reproduced
     on the unpatched kernel and verified to be fixed by this series.

   - ia64, microblaze, nios2, openrisc: build, but otherwise completely
     untested"

* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  openrisc: fix livelock in uaccess
  nios2: fix livelock in uaccess
  microblaze: fix livelock in uaccess
  ia64: fix livelock in uaccess
  sparc: fix livelock in uaccess
  alpha: fix livelock in uaccess
  parisc: fix livelock in uaccess
  hexagon: fix livelock in uaccess
  riscv: fix livelock in uaccess
  m68k: fix livelock in uaccess

include/linux/compiler-intel.h had no update in the past 3 years.

We often forget about the third C compiler to build the kernel.

For example, commit a0a12c3e ("asm goto: eradicate CC_HAS_ASM_GOTO")
only mentioned GCC and Clang.

init/Kconfig defines CC_IS_GCC and CC_IS_CLANG but not CC_IS_ICC,
and nobody has reported any issue.

I guess the Intel Compiler support is broken, and nobody is caring
about it.

Harald Arnesen pointed out ICC (classic Intel C/C++ compiler) is
deprecated:

    $ icc -v
    icc: remark #10441: The Intel(R) C++ Compiler Classic (ICC) is
    deprecated and will be removed from product release in the second half
    of 2023. The Intel(R) oneAPI DPC++/C++ Compiler (ICX) is the recommended
    compiler moving forward. Please transition to use this compiler. Use
    '-diag-disable=10441' to disable this message.
    icc version 2021.7.0 (gcc version 12.1.0 compatibility)

Arnd Bergmann provided a link to the article, "Intel C/C++ compilers
complete adoption of LLVM".

lib/zstd/common/compiler.h and lib/zstd/compress/zstd_fast.c were kept
untouched for better sync with https://github.com/facebook/zstd

Link: https://www.intel.com/content/www/us/en/developer/articles/technical/adoption-of-llvm-complete-icx.htmlSigned-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull more i2c updates from Wolfram Sang:
 "Some improvements/fixes for the newly added GXP driver and a Kconfig
  dependency fix"

* tag 'i2c-for-6.3-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: gxp: fix an error code in probe
  i2c: gxp: return proper error on address NACK
  i2c: gxp: remove "empty" switch statement
  i2c: Disable I2C_APPLE when I2C_PASEMI is a builtin

The migration code ends up temporarily stashing information of the wrong
type in unused fields of the newly allocated destination folio.  That
all works fine, but gcc does complain about the pointer type mis-use:

    mm/migrate.c: In function ‘__migrate_folio_extract’:
    mm/migrate.c:1050:20: note: randstruct: casting between randomized structure pointer types (ssa): ‘struct anon_vma’ and ‘struct address_space’

     1050 |         *anon_vmap = (void *)dst->mapping;
          |         ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

and gcc is actually right to complain since it really doesn't understand
that this is a very temporary special case where this is ok.

This could be fixed in different ways by just obfuscating the assignment
sufficiently that gcc doesn't see what is going on, but the truly
"proper C" way to do this is by explicitly using a union.

Using unions for type conversions like this is normally hugely ugly and
syntactically nasty, but this really is one of the few cases where we
want to make it clear that we're not doing type conversion, we're really
re-using the value bit-for-bit just using another type.

IOW, this should not become a common pattern, but in this one case using
that odd union is probably the best way to document to the compiler what
is conceptually going on here.

[ Side note: there are valid cases where we convert pointers to other
  pointer types, notably the whole "folio vs page" situation, where the
  types actually have fundamental commonalities.

  The fact that the gcc note is limited to just randomized structures
  means that we don't see equivalent warnings for those cases, but it
  migth also mean that we miss other cases where we do play these kinds
  of dodgy games, and this kind of explicit conversion might be a good
  idea. ]

I verified that at least for an allmodconfig build on x86-64, this
generates the exact same code, apart from line numbers and assembler
comment changes.

Fixes: 64c8902e ("migrate_pages: split unmap_and_move() to _unmap() and _move()")
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'mm-hotfixes-stable-2023-03-04-13-12' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull misc fixes from Andrew Morton:
 "17 hotfixes.

  Eight are for MM and seven are for other parts of the kernel. Seven
  are cc:stable and eight address post-6.3 issues or were judged
  unsuitable for -stable backporting"

* tag 'mm-hotfixes-stable-2023-03-04-13-12' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  mailmap: map Dikshita Agarwal's old address to his current one
  mailmap: map Vikash Garodia's old address to his current one
  fs/cramfs/inode.c: initialize file_ra_state
  fs: hfsplus: fix UAF issue in hfsplus_put_super
  panic: fix the panic_print NMI backtrace setting
  lib: parser: update documentation for match_NUMBER functions
  kasan, x86: don't rename memintrinsics in uninstrumented files
  kasan: test: fix test for new meminstrinsic instrumentation
  kasan: treat meminstrinsic as builtins in uninstrumented files
  kasan: emit different calls for instrumentable memintrinsics
  ocfs2: fix non-auto defrag path not working issue
  ocfs2: fix defrag path triggering jbd2 ASSERT
  mailmap: map Georgi Djakov's old Linaro address to his current one
  mm/hwpoison: convert TTU_IGNORE_HWPOISON to TTU_HWPOISON
  lib/zlib: DFLTCC deflate does not write all available bits for Z_NO_FLUSH
  mm/damon/paddr: fix missing folio_put()
  mm/mremap: fix dup_anon_vma() in vma_merge() case 4

Pull powerpc fixes from Michael Ellerman:

 - Drop orphaned VAS MAINTAINERS entry

 - Fix build errors with clang and KCSAN

 - Avoid build errors seen with LD_DEAD_CODE_DATA_ELIMINATION together
   with recordmcount

Thanks to Nathan Chancellor.

* tag 'powerpc-6.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc: Avoid dead code/data elimination when using recordmcount
  powerpc/vmlinux.lds: Add .text.asan/tsan sections
  powerpc: Drop orphaned VAS MAINTAINERS entry

Pull sound fixes from Takashi Iwai:
 "A collection of various small fixes that have been gathered since the
  last PR.

  The majority of changes are for ASoC, and there is a small change in
  ASoC PCM core, but the rest are all for driver- specific fixes /
  quirks / updates"

* tag 'sound-fix-6.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: (32 commits)
  ALSA: ice1712: Delete unreachable code in aureon_add_controls()
  ALSA: ice1712: Do not left ice->gpio_mutex locked in aureon_add_controls()
  ALSA: hda/realtek: Add quirk for HP EliteDesk 800 G6 Tower PC
  ALSA: hda/realtek: Improve support for Dell Precision 3260
  ASoC: mediatek: mt8195: add missing initialization
  ASoC: mediatek: mt8188: add missing initialization
  ASoC: amd: yc: Add DMI entries to support HP OMEN 16-n0xxx (8A43)
  ASoC: zl38060 add gpiolib dependency
  ASoC: sam9g20ek: Disable capture unless building with microphone input
  ASoC: mt8192: Fix range for sidetone positive gain
  ASoC: mt8192: Report an error if when an invalid sidetone gain is written
  ASoC: mt8192: Fix event generation for controls
  ASoC: mt8192: Remove spammy log messages
  ASoC: mchp-pdmc: fix poc noise at capture startup
  ASoC: dt-bindings: sama7g5-pdmc: add microchip,startup-delay-us binding
  ASoC: soc-pcm: add option to start DMA after DAI
  ASoC: mt8183: Fix event generation for I2S DAI operations
  ASoC: mt8183: Remove spammy logging from I2S DAI driver
  ASoC: mt6358: Remove undefined HPx Mux enumeration values
  ASoC: mt6358: Validate Wake on Voice 2 writes
  ...

Pull more power supply updates from Sebastian Reichel:

 - Fix DT binding for Richtek RT9467

 - Fix a NULL pointer check in the power-supply core

 - Document meaning of absent "present" property

* tag 'for-v6.3-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply:
  dt-bindings: power: supply: Revise Richtek RT9467 compatible name
  ABI: testing: sysfs-class-power: Document absence of "present" property
  power: supply: fix null pointer check order in __power_supply_register

Pull more cifs updates from Steve French:

 - xfstest generic/208 fix (memory leak)

 - minor netfs fix (to address smatch warning)

 - a DFS fix for stable

 - a reconnect race fix

 - two multichannel fixes

 - RDMA (smbdirect) fix

 - two additional writeback fixes from David

* tag '6.3-rc-smb3-client-fixes-part2' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: Fix memory leak in direct I/O
  cifs: prevent data race in cifs_reconnect_tcon()
  cifs: improve checking of DFS links over STATUS_OBJECT_NAME_INVALID
  iov: Fix netfs_extract_user_to_sg()
  cifs: Fix cifs_write_back_from_locked_folio()
  cifs: reuse cifs_match_ipaddr for comparison of dstaddr too
  cifs: match even the scope id for ipv6 addresses
  cifs: Fix an uninitialised variable
  cifs: Add some missing xas_retry() calls

The usermodehelper code uses two fake pointers for the two capability
cases: CAP_BSET for reading and writing 'usermodehelper_bset', and
CAP_PI to read and write 'usermodehelper_inheritable'.

This seems to be a completely unnecessary indirection, since we could
instead just use the pointers themselves, and never have to do any "if
this then that" kind of logic.

So just get rid of the fake pointer values, and use the real pointer
values instead.
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull coccinelle updates from Julia Lawall:
 "Changes in make coccicheck and improve a semantic patch

  This makes a couple of changes in make coccicheck related to shell
  commands.

  It also updates the api/atomic_as_refcounter semantic patch to include
  WARNING in the output message, as done in other cases"

* tag 'cocci-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jlawall/linux:
  scripts: coccicheck: Use /usr/bin/env
  scripts: coccicheck: Avoid warning about spurious escape
  coccinelle: api/atomic_as_refcounter: include message type in output

Pull Rust fix from Miguel Ojeda:
 "A single build error fix: there was a change during the merge window
  to a C header parsed by the Rust bindings generator, introducing a
  type that it does not handle well.

  The fix tells the generator to treat the type as opaque (for now)"

* tag 'rust-fixes-6.3-rc1' of https://github.com/Rust-for-Linux/linux:
  rust: bindgen: Add `alt_instr` as opaque type

Pull more SCSI updates from James Bottomley:
 "Updates that missed the first pull, mostly because of needing more
  soak time.

  Driver updates (zfcp, ufs, mpi3mr, plus two ipr bug fixes), an
  enclosure services (ses) update (mostly bug fixes) and other minor bug
  fixes and changes"

* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (32 commits)
  scsi: zfcp: Trace when request remove fails after qdio send fails
  scsi: zfcp: Change the type of all fsf request id fields and variables to u64
  scsi: zfcp: Make the type for accessing request hashtable buckets size_t
  scsi: ufs: core: Simplify ufshcd_execute_start_stop()
  scsi: ufs: core: Rely on the block layer for setting RQF_PM
  scsi: core: Extend struct scsi_exec_args
  scsi: lpfc: Fix double word in comments
  scsi: core: Remove the /proc/scsi/${proc_name} directory earlier
  scsi: core: Fix a source code comment
  scsi: cxgbi: Remove unneeded version.h include
  scsi: qedi: Remove unneeded version.h include
  scsi: mpi3mr: Remove unneeded version.h include
  scsi: mpi3mr: Fix missing mrioc->evtack_cmds initialization
  scsi: mpi3mr: Use number of bits to manage bitmap sizes
  scsi: mpi3mr: Remove unnecessary memcpy() to alltgt_info->dmi
  scsi: mpi3mr: Fix issues in mpi3mr_get_all_tgt_info()
  scsi: mpi3mr: Fix an issue found by KASAN
  scsi: mpi3mr: Replace 1-element array with flex-array
  scsi: ipr: Work around fortify-string warning
  scsi: ipr: Make ipr_probe_ioa_part2() return void
  ...

This is passing IS_ERR() instead of PTR_ERR() so instead of an error
code it prints and returns the number 1.

Fixes: 4a55ed6f ("i2c: Add GXP SoC I2C Controller")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Nick Hawkins <nick.hawkins@hpe.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

According to Documentation/i2c/fault-codes.rst, NACK after sending an
address should be -ENXIO.
Signed-off-by: Wolfram Sang <wsa@kernel.org>

There used to be error messages which had to go. Now, it only consists
of 'break's, so it can go.
Signed-off-by: Wolfram Sang <wsa@kernel.org>

The ppc64le_allmodconfig sets I2C_PASEMI=y and leaves COMPILE_TEST to
default to y and I2C_APPLE to default to m, running into a known
incompatible configuration that breaks the build [1]. Specifically,
a common dependency (i2c-pasemi-core.o in this case) cannot be used by
both builtin and module consumers.

Disable I2C_APPLE when I2C_PASEMI is a builtin to prevent this.

[1]: https://lore.kernel.org/all/202112061809.XT99aPrf-lkp@intel.comSuggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sven Peter <sven@svenpeter.dev>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Pull more thermal control updates from Rafael Wysocki:
 "These fix two issues in the Intel thermal control drivers.

  Specifics:

   - Fix an error pointer dereference in the quark_dts Intel thermal
     driver (Dan Carpenter)

   - Fix the intel_bxt_pmic_thermal driver Kconfig entry to select
     REGMAP which is not user-visible instead of depending on it (Randy
     Dunlap)"

* tag 'thermal-6.3-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  thermal: intel: BXT_PMIC: select REGMAP instead of depending on it
  thermal: intel: quark_dts: fix error pointer dereference

Pull more ACPI updates from Rafael Wysocki:
 "These update ACPI quirks for some x86 platforms and add an IRQ
  override quirk for one more system.

  Specifics:

   - Add an ACPI IRQ override quirk for Asus Expertbook B2402FBA
     (Vojtech Hejsek)

   - Drop a suspend-to-idle quirk for HP Elitebook G9 that is not needed
     any more after a firmware update (Mario Limonciello)

   - Add all Cezanne systems to the list for forcing StorageD3Enable,
     because they all need the same quirk (Mario Limonciello)"

* tag 'acpi-6.3-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI: x86: utils: Add Cezanne to the list for forcing StorageD3Enable
  ACPI: x86: Drop quirk for HP Elitebook
  ACPI: resource: Skip IRQ override on Asus Expertbook B2402FBA

Pull more power management updates from Rafael Wysocki:
 "These update power capping (new hardware support and cleanup) and
  cpufreq (bug fixes, cleanups and intel_pstate adjustment for a new
  platform).

  Specifics:

   - Fix error handling in the apple-soc cpufreq driver (Dan Carpenter)

   - Change the log level of a message in the amd-pstate cpufreq driver
     so it is more visible to users (Kai-Heng Feng)

   - Adjust the balance_performance EPP value for Sapphire Rapids in the
     intel_pstate cpufreq driver (Srinivas Pandruvada)

   - Remove MODULE_LICENSE from 3 pieces of non-modular code (Nick
     Alcock)

   - Make a read-only kobj_type structure in the schedutil cpufreq
     governor constant (Thomas Weißschuh)

   - Add Add Power Limit4 support for Meteor Lake SoC to the Intel RAPL
     power capping driver (Sumeet Pawnikar)"

* tag 'pm-6.3-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  cpufreq: apple-soc: Fix an IS_ERR() vs NULL check
  powercap: remove MODULE_LICENSE in non-modules
  cpufreq: intel_pstate: remove MODULE_LICENSE in non-modules
  powercap: RAPL: Add Power Limit4 support for Meteor Lake SoC
  cpufreq: amd-pstate: remove MODULE_LICENSE in non-modules
  cpufreq: schedutil: make kobj_type structure constant
  cpufreq: amd-pstate: Let user know amd-pstate is disabled
  cpufreq: intel_pstate: Adjust balance_performance EPP for Sapphire Rapids

Pull more io_uring updates from Jens Axboe:
 "Here's a set of fixes/changes that didn't make the first cut, either
  because they got queued before I sent the early merge request, or
  fixes that came in afterwards. In detail:

   - Don't set MSG_NOSIGNAL on recv/recvmsg opcodes, as AF_PACKET will
     error out (David)

   - Fix for spurious poll wakeups (me)

   - Fix for a file leak for buffered reads in certain conditions
     (Joseph)

   - Don't allow registered buffers of mixed types (Pavel)

   - Improve handling of huge pages for registered buffers (Pavel)

   - Provided buffer ring size calculation fix (Wojciech)

   - Minor cleanups (me)"

* tag 'io_uring-6.3-2023-03-03' of git://git.kernel.dk/linux:
  io_uring/poll: don't pass in wake func to io_init_poll_iocb()
  io_uring: fix fget leak when fs don't support nowait buffered read
  io_uring/poll: allow some retries for poll triggering spuriously
  io_uring: remove MSG_NOSIGNAL from recvmsg
  io_uring/rsrc: always initialize 'folio' to NULL
  io_uring/rsrc: optimise registered huge pages
  io_uring/rsrc: optimise single entry advance
  io_uring/rsrc: disallow multi-source reg buffers
  io_uring: remove unused wq_list_merge
  io_uring: fix size calculation when registering buf ring
  io_uring/rsrc: fix a comment in io_import_fixed()
  io_uring: rename 'in_idle' to 'in_cancel'
  io_uring: consolidate the put_ref-and-return section of adding work

Pull block fixes from Jens Axboe:

 - NVMe pull request via Christoph:
      - Don't access released socket during error recovery (Akinobu
        Mita)
      - Bring back auto-removal of deleted namespaces during sequential
        scan (Christoph Hellwig)
      - Fix an error code in nvme_auth_process_dhchap_challenge (Dan
        Carpenter)
      - Show well known discovery name (Daniel Wagner)
      - Add a missing endianess conversion in effects masking (Keith
        Busch)

 - Fix for a regression introduced in blk-rq-qos during init in this
   merge window (Breno)

 - Reorder a few fields in struct blk_mq_tag_set, eliminating a few
   holes and shrinking it (Christophe)

 - Remove redundant bdev_get_queue() NULL checks (Juhyung)

 - Add sed-opal single user mode support flag (Luca)

 - Remove SQE128 check in ublk as it isn't needed, saving some memory
   (Ming)

 - Op specific segment checking for cloned requests (Uday)

 - Exclusive open partition scan fixes (Yu)

 - Loop offset/size checking before assigning them in the device (Zhong)

 - Bio polling fixes (me)

* tag 'block-6.3-2023-03-03' of git://git.kernel.dk/linux:
  blk-mq: enforce op-specific segment limits in blk_insert_cloned_request
  nvme-fabrics: show well known discovery name
  nvme-tcp: don't access released socket during error recovery
  nvme-auth: fix an error code in nvme_auth_process_dhchap_challenge()
  nvme: bring back auto-removal of deleted namespaces during sequential scan
  blk-iocost: Pass gendisk to ioc_refresh_params
  nvme: fix sparse warning on effects masking
  block: be a bit more careful in checking for NULL bdev while polling
  block: clear bio->bi_bdev when putting a bio back in the cache
  loop: loop_set_status_from_info() check before assignment
  ublk: remove check IO_URING_F_SQE128 in ublk_ch_uring_cmd
  block: remove more NULL checks after bdev_get_queue()
  blk-mq: Reorder fields in 'struct blk_mq_tag_set'
  block: fix scan partition for exclusively open device again
  block: Revert "block: Do not reread partition table on exclusively open device"
  sed-opal: add support flag for SUM in status ioctl

Pull ATA fix from Damien Le Moal:

 - Revert commit 104ff59a ("ata: ahci: Add Tiger Lake UP{3,4} AHCI
   controller") as it is causing serious regressions (failure to boot)
   on some laptops

* tag 'ata-6.3-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/libata:
  ata: ahci: Revert "ata: ahci: Add Tiger Lake UP{3,4} AHCI controller"

Merge additional ACPI quirks for x86 systems:

 - Drop a suspend-to-idle quirk for HP Elitebook G9 that is not needed
   any more after a firmware update (Mario Limonciello).

 - Add all Cezanne systems to the list for forcing StorageD3Enable,
   because they all need the same quirk (Mario Limonciello).

* acpi-pm:
  ACPI: x86: Drop quirk for HP Elitebook

* acpi-x86:
  ACPI: x86: utils: Add Cezanne to the list for forcing StorageD3Enable

Pull more s390 updates from Heiko Carstens:

 - Add empty command line parameter handling stubs to kernel for all
   command line parameters which are handled in the decompressor. This
   avoids invalid "Unknown kernel command line parameters" messages from
   the kernel, and also avoids that these will be incorrectly passed to
   user space. This caused already confusion, therefore add the empty
   stubs

 - Add missing phys_to_virt() handling to machine check handler

 - Introduce and use a union to be used for zcrypt inline assemblies.
   This makes sure that only a register wide member of the union is
   passed as input and output parameter to inline assemblies, while
   usual C code uses other members of the union to access bit fields of
   it

 - Add and use a READ_ONCE_ALIGNED_128() macro, which can be used to
   atomically read a 128-bit value from memory. This replaces the
   (mis-)use of the 128-bit cmpxchg operation to do the same in cpum_sf
   code. Currently gcc does not generate the used lpq instruction if
   __READ_ONCE() is used for aligned 128-bit accesses, therefore use
   this s390 specific helper

 - Simplify machine check handler code if a task needs to be killed
   because of e.g. register corruption due to a machine malfunction

 - Perform CPU reset to clear pending interrupts and TLB entries on an
   already stopped target CPU before delegating work to it

 - Generate arch/s390/boot/vmlinux.map link map for the decompressor,
   when CONFIG_VMLINUX_MAP is enabled for debugging purposes

 - Fix segment type handling for dcssblk devices. It incorrectly always
   returned type "READ/WRITE" even for read-only segements, which can
   result in a kernel panic if somebody tries to write to a read-only
   device

 - Sort config S390 select list again

 - Fix two kprobe reenter bugs revealed by a recently added kprobe kunit
   test

* tag 's390-6.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/kprobes: fix current_kprobe never cleared after kprobes reenter
  s390/kprobes: fix irq mask clobbering on kprobe reenter from post_handler
  s390/Kconfig: sort config S390 select list again
  s390/extmem: return correct segment type in __segment_load()
  s390/decompressor: add link map saving
  s390/smp: perform cpu reset before delegating work to target cpu
  s390/mcck: cleanup user process termination path
  s390/cpum_sf: use READ_ONCE_ALIGNED_128() instead of 128-bit cmpxchg
  s390/rwonce: add READ_ONCE_ALIGNED_128() macro
  s390/ap,zcrypt,vfio: introduce and use ap_queue_status_reg union
  s390/nmi: fix virtual-physical address confusion
  s390/setup: do not complain about parameters handled in decompressor

Pull more RISC-V updates from Palmer Dabbelt:

 - Some cleanups and fixes for the Zbb-optimized string routines

 - Support for custom (vendor or implementation defined) perf events

 - COMMAND_LINE_SIZE has been increased to 1024

* tag 'riscv-for-linus-6.3-mw2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: Bump COMMAND_LINE_SIZE value to 1024
  drivers/perf: RISC-V: Allow programming custom firmware events
  riscv, lib: Fix Zbb strncmp
  RISC-V: improve string-function assembly