linux.git/arch/alpha/include, branch v5.4.293

alpha: make stack 16-byte aligned (most cases)

2025-03-13T11:43:16+00:00

commit 0a0f7362b0367634a2d5cb7c96226afc116f19c9 upstream.

The problem is that GCC expects 16-byte alignment of the incoming stack
since early 2004, as Maciej found out [1]:
  Having actually dug speculatively I can see that the psABI was changed in
 GCC 3.5 with commit e5e10fb4a350 ("re PR target/14539 (128-bit long double
 improperly aligned)") back in Mar 2004, when the stack pointer alignment
 was increased from 8 bytes to 16 bytes, and arch/alpha/kernel/entry.S has
 various suspicious stack pointer adjustments, starting with SP_OFF which
 is not a whole multiple of 16.

Also, as Magnus noted, "ALPHA Calling Standard" [2] required the same:
 D.3.1 Stack Alignment
  This standard requires that stacks be octaword aligned at the time a
  new procedure is invoked.

However:
- the "normal" kernel stack is always misaligned by 8 bytes, thanks to
  the odd number of 64-bit words in 'struct pt_regs', which is the very
  first thing pushed onto the kernel thread stack;
- syscall, fault, interrupt etc. handlers may, or may not, receive aligned
  stack depending on numerous factors.

Somehow we got away with it until recently, when we ended up with
a stack corruption in kernel/smp.c:smp_call_function_single() due to
its use of 32-byte aligned local data and the compiler doing clever
things allocating it on the stack.

This adds padding between the PAL-saved and kernel-saved registers
so that 'struct pt_regs' have an even number of 64-bit words.
This makes the stack properly aligned for most of the kernel
code, except two handlers which need special threatment.

Note: struct pt_regs doesn't belong in uapi/asm; this should be fixed,
but let's put this off until later.

Link: https://lore.kernel.org/rcu/alpine.DEB.2.21.2501130248010.18889@angie.orcam.me.uk/ [1]
Link: https://bitsavers.org/pdf/dec/alpha/Alpha_Calling_Standard_Rev_2.0_19900427.pdf [2]

Cc: stable@vger.kernel.org
Tested-by: Maciej W. Rozycki 
Tested-by: Magnus Lindholm 
Tested-by: Matt Turner 
Reviewed-by: Maciej W. Rozycki 
Signed-off-by: Ivan Kokshaysky 
Signed-off-by: Matt Turner 
Signed-off-by: Greg Kroah-Hartman

init: Remove check_bugs() leftovers

2023-08-08T17:56:34+00:00

commit 61235b24b9cb37c13fcad5b9596d59a1afdcec30 upstream

Everything is converted over to arch_cpu_finalize_init(). Remove the
check_bugs() leftovers including the empty stubs in asm-generic, alpha,
parisc, powerpc and xtensa.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Richard Henderson 
Link: https://lore.kernel.org/r/20230613224545.553215951@linutronix.de
Signed-off-by: Daniel Sneddon 
Signed-off-by: Greg Kroah-Hartman

alpha: define get_cycles macro for arch-override

2022-06-22T12:11:14+00:00

commit 1097710bc9660e1e588cf2186a35db3d95c4d258 upstream.

Alpha defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner 
Cc: Arnd Bergmann 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Acked-by: Matt Turner 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

alpha: Declare virt_to_phys and virt_to_bus parameter as pointer to volatile

2021-09-30T08:09:26+00:00

[ Upstream commit 35a3f4ef0ab543daa1725b0c963eb8c05e3376f8 ]

Some drivers pass a pointer to volatile data to virt_to_bus() and
virt_to_phys(), and that works fine.  One exception is alpha.  This
results in a number of compile errors such as

  drivers/net/wan/lmc/lmc_main.c: In function 'lmc_softreset':
  drivers/net/wan/lmc/lmc_main.c:1782:50: error:
	passing argument 1 of 'virt_to_bus' discards 'volatile'
	qualifier from pointer target type

  drivers/atm/ambassador.c: In function 'do_loader_command':
  drivers/atm/ambassador.c:1747:58: error:
	passing argument 1 of 'virt_to_bus' discards 'volatile'
	qualifier from pointer target type

Declare the parameter of virt_to_phys and virt_to_bus as pointer to
volatile to fix the problem.

Signed-off-by: Guenter Roeck 
Acked-by: Arnd Bergmann 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

alpha: fix annotation of io{read,write}{16,32}be()

2020-08-26T08:40:58+00:00

[ Upstream commit bd72866b8da499e60633ff28f8a4f6e09ca78efe ]

These accessors must be used to read/write a big-endian bus.  The value
returned or written is native-endian.

However, these accessors are defined using be{16,32}_to_cpu() or
cpu_to_be{16,32}() to make the endian conversion but these expect a
__be{16,32} when none is present.  Keeping them would need a force cast
that would solve nothing at all.

So, do the conversion using swab{16,32}, like done in asm-generic for
similar situations.

Reported-by: kernel test robot 
Signed-off-by: Luc Van Oostenryck 
Signed-off-by: Andrew Morton 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Matt Turner 
Cc: Stephen Boyd 
Cc: Arnd Bergmann 
Link: http://lkml.kernel.org/r/20200622114232.80039-1-luc.vanoostenryck@gmail.com
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

alpha: fix memory barriers so that they conform to the specification

2020-06-22T07:31:21+00:00

commit 54505a1e2083fc54cbe8779b97479f969cd30a00 upstream.

The commits cd0e00c10672 and 92d7223a7423 broke boot on the Alpha Avanti
platform. The patches move memory barriers after a write before the write.
The result is that if there's iowrite followed by ioread, there is no
barrier between them.

The Alpha architecture allows reordering of the accesses to the I/O space,
and the missing barrier between write and read causes hang with serial
port and real time clock.

This patch makes barriers confiorm to the specification.

1. We add mb() before readX_relaxed and writeX_relaxed -
   memory-barriers.txt claims that these functions must be ordered w.r.t.
   each other. Alpha doesn't order them, so we need an explicit barrier.
2. We add mb() before reads from the I/O space - so that if there's a
   write followed by a read, there should be a barrier between them.

Signed-off-by: Mikulas Patocka 
Fixes: cd0e00c10672 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering")
Fixes: 92d7223a7423 ("alpha: io: reorder barriers to guarantee writeX() and iowriteX() ordering #2")
Cc: stable@vger.kernel.org      # v4.17+
Acked-by: Ivan Kokshaysky 
Reviewed-by: Maciej W. Rozycki 
Signed-off-by: Matt Turner 
Signed-off-by: Greg Kroah-Hartman

mm: introduce MADV_PAGEOUT

2019-09-26T00:51:41+00:00

When a process expects no accesses to a certain memory range for a long
time, it could hint kernel that the pages can be reclaimed instantly but
data should be preserved for future use.  This could reduce workingset
eviction so it ends up increasing performance.

This patch introduces the new MADV_PAGEOUT hint to madvise(2) syscall.
MADV_PAGEOUT can be used by a process to mark a memory range as not
expected to be used for a long time so that kernel reclaims *any LRU*
pages instantly.  The hint can help kernel in deciding which pages to
evict proactively.

A note: It doesn't apply SWAP_CLUSTER_MAX LRU page isolation limit
intentionally because it's automatically bounded by PMD size.  If PMD
size(e.g., 256) makes some trouble, we could fix it later by limit it to
SWAP_CLUSTER_MAX[1].

- man-page material

MADV_PAGEOUT (since Linux x.x)

Do not expect access in the near future so pages in the specified
regions could be reclaimed instantly regardless of memory pressure.
Thus, access in the range after successful operation could cause
major page fault but never lose the up-to-date contents unlike
MADV_DONTNEED. Pages belonging to a shared mapping are only processed
if a write access is allowed for the calling process.

MADV_PAGEOUT cannot be applied to locked pages, Huge TLB pages, or
VM_PFNMAP pages.

[1] https://lore.kernel.org/lkml/20190710194719.GS29695@dhcp22.suse.cz/

[minchan@kernel.org: clear PG_active on MADV_PAGEOUT]
  Link: http://lkml.kernel.org/r/20190802200643.GA181880@google.com
[akpm@linux-foundation.org: resolve conflicts with hmm.git]
Link: http://lkml.kernel.org/r/20190726023435.214162-5-minchan@kernel.org
Signed-off-by: Minchan Kim 
Reported-by: kbuild test robot 
Acked-by: Michal Hocko 
Cc: James E.J. Bottomley 
Cc: Richard Henderson 
Cc: Ralf Baechle 
Cc: Chris Zankel 
Cc: Daniel Colascione 
Cc: Dave Hansen 
Cc: Hillf Danton 
Cc: Joel Fernandes (Google) 
Cc: Johannes Weiner 
Cc: Kirill A. Shutemov 
Cc: Oleksandr Natalenko 
Cc: Shakeel Butt 
Cc: Sonny Rao 
Cc: Suren Baghdasaryan 
Cc: Tim Murray 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: introduce MADV_COLD

2019-09-26T00:51:41+00:00

Patch series "Introduce MADV_COLD and MADV_PAGEOUT", v7.

- Background

The Android terminology used for forking a new process and starting an app
from scratch is a cold start, while resuming an existing app is a hot
start.  While we continually try to improve the performance of cold
starts, hot starts will always be significantly less power hungry as well
as faster so we are trying to make hot start more likely than cold start.

To increase hot start, Android userspace manages the order that apps
should be killed in a process called ActivityManagerService.
ActivityManagerService tracks every Android app or service that the user
could be interacting with at any time and translates that into a ranked
list for lmkd(low memory killer daemon).  They are likely to be killed by
lmkd if the system has to reclaim memory.  In that sense they are similar
to entries in any other cache.  Those apps are kept alive for
opportunistic performance improvements but those performance improvements
will vary based on the memory requirements of individual workloads.

- Problem

Naturally, cached apps were dominant consumers of memory on the system.
However, they were not significant consumers of swap even though they are
good candidate for swap.  Under investigation, swapping out only begins
once the low zone watermark is hit and kswapd wakes up, but the overall
allocation rate in the system might trip lmkd thresholds and cause a
cached process to be killed(we measured performance swapping out vs.
zapping the memory by killing a process.  Unsurprisingly, zapping is 10x
times faster even though we use zram which is much faster than real
storage) so kill from lmkd will often satisfy the high zone watermark,
resulting in very few pages actually being moved to swap.

- Approach

The approach we chose was to use a new interface to allow userspace to
proactively reclaim entire processes by leveraging platform information.
This allowed us to bypass the inaccuracy of the kernel’s LRUs for pages
that are known to be cold from userspace and to avoid races with lmkd by
reclaiming apps as soon as they entered the cached state.  Additionally,
it could provide many chances for platform to use much information to
optimize memory efficiency.

To achieve the goal, the patchset introduce two new options for madvise.
One is MADV_COLD which will deactivate activated pages and the other is
MADV_PAGEOUT which will reclaim private pages instantly.  These new
options complement MADV_DONTNEED and MADV_FREE by adding non-destructive
ways to gain some free memory space.  MADV_PAGEOUT is similar to
MADV_DONTNEED in a way that it hints the kernel that memory region is not
currently needed and should be reclaimed immediately; MADV_COLD is similar
to MADV_FREE in a way that it hints the kernel that memory region is not
currently needed and should be reclaimed when memory pressure rises.

This patch (of 5):

When a process expects no accesses to a certain memory range, it could
give a hint to kernel that the pages can be reclaimed when memory pressure
happens but data should be preserved for future use.  This could reduce
workingset eviction so it ends up increasing performance.

This patch introduces the new MADV_COLD hint to madvise(2) syscall.
MADV_COLD can be used by a process to mark a memory range as not expected
to be used in the near future.  The hint can help kernel in deciding which
pages to evict early during memory pressure.

It works for every LRU pages like MADV_[DONTNEED|FREE]. IOW, It moves

	active file page -> inactive file LRU
	active anon page -> inacdtive anon LRU

Unlike MADV_FREE, it doesn't move active anonymous pages to inactive file
LRU's head because MADV_COLD is a little bit different symantic.
MADV_FREE means it's okay to discard when the memory pressure because the
content of the page is *garbage* so freeing such pages is almost zero
overhead since we don't need to swap out and access afterward causes just
minor fault.  Thus, it would make sense to put those freeable pages in
inactive file LRU to compete other used-once pages.  It makes sense for
implmentaion point of view, too because it's not swapbacked memory any
longer until it would be re-dirtied.  Even, it could give a bonus to make
them be reclaimed on swapless system.  However, MADV_COLD doesn't mean
garbage so reclaiming them requires swap-out/in in the end so it's bigger
cost.  Since we have designed VM LRU aging based on cost-model, anonymous
cold pages would be better to position inactive anon's LRU list, not file
LRU.  Furthermore, it would help to avoid unnecessary scanning if system
doesn't have a swap device.  Let's start simpler way without adding
complexity at this moment.  However, keep in mind, too that it's a caveat
that workloads with a lot of pages cache are likely to ignore MADV_COLD on
anonymous memory because we rarely age anonymous LRU lists.

* man-page material

MADV_COLD (since Linux x.x)

Pages in the specified regions will be treated as less-recently-accessed
compared to pages in the system with similar access frequencies.  In
contrast to MADV_FREE, the contents of the region are preserved regardless
of subsequent writes to pages.

MADV_COLD cannot be applied to locked pages, Huge TLB pages, or VM_PFNMAP
pages.

[akpm@linux-foundation.org: resolve conflicts with hmm.git]
Link: http://lkml.kernel.org/r/20190726023435.214162-2-minchan@kernel.org
Signed-off-by: Minchan Kim 
Reported-by: kbuild test robot 
Acked-by: Michal Hocko 
Acked-by: Johannes Weiner 
Cc: James E.J. Bottomley 
Cc: Richard Henderson 
Cc: Ralf Baechle 
Cc: Chris Zankel 
Cc: Johannes Weiner 
Cc: Daniel Colascione 
Cc: Dave Hansen 
Cc: Hillf Danton 
Cc: Joel Fernandes (Google) 
Cc: Kirill A. Shutemov 
Cc: Oleksandr Natalenko 
Cc: Shakeel Butt 
Cc: Sonny Rao 
Cc: Suren Baghdasaryan 
Cc: Tim Murray 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: consolidate pgtable_cache_init() and pgd_cache_init()

2019-09-24T22:54:09+00:00

Both pgtable_cache_init() and pgd_cache_init() are used to initialize kmem
cache for page table allocations on several architectures that do not use
PAGE_SIZE tables for one or more levels of the page table hierarchy.

Most architectures do not implement these functions and use __weak default
NOP implementation of pgd_cache_init().  Since there is no such default
for pgtable_cache_init(), its empty stub is duplicated among most
architectures.

Rename the definitions of pgd_cache_init() to pgtable_cache_init() and
drop empty stubs of pgtable_cache_init().

Link: http://lkml.kernel.org/r/1566457046-22637-1-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport 
Acked-by: Will Deacon 		[arm64]
Acked-by: Thomas Gleixner 	[x86]
Cc: Catalin Marinas 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove quicklist page table caches

2019-09-24T22:54:09+00:00

Patch series "mm: remove quicklist page table caches".

A while ago Nicholas proposed to remove quicklist page table caches [1].

I've rebased his patch on the curren upstream and switched ia64 and sh to
use generic versions of PTE allocation.

[1] https://lore.kernel.org/linux-mm/20190711030339.20892-1-npiggin@gmail.com

This patch (of 3):

Remove page table allocator "quicklists".  These have been around for a
long time, but have not got much traction in the last decade and are only
used on ia64 and sh architectures.

The numbers in the initial commit look interesting but probably don't
apply anymore.  If anybody wants to resurrect this it's in the git
history, but it's unhelpful to have this code and divergent allocator
behaviour for minor archs.

Also it might be better to instead make more general improvements to page
allocator if this is still so slow.

Link: http://lkml.kernel.org/r/1565250728-21721-2-git-send-email-rppt@linux.ibm.com
Signed-off-by: Nicholas Piggin 
Signed-off-by: Mike Rapoport 
Cc: Tony Luck 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds