linux.git/kernel/dma/pool.c, branch v6.6.132

dma/pool: distinguish between missing and exhausted atomic pools

2026-02-06T15:48:24+00:00

[ Upstream commit 56c430c7f06d838fe3b2077dbbc4cc0bf992312b ]

Currently, dma_alloc_from_pool() unconditionally warns and dumps a stack
trace when an allocation fails, with the message "Failed to get suitable
pool".

This conflates two distinct failure modes:
1. Configuration error: No atomic pool is available for the requested
   DMA mask (a fundamental system setup issue)
2. Resource Exhaustion: A suitable pool exists but is currently full (a
   recoverable runtime state)

This lack of distinction prevents drivers from using __GFP_NOWARN to
suppress error messages during temporary pressure spikes, such as when
awaiting synchronous reclaim of descriptors.

Refactor the error handling to distinguish these cases:
- If no suitable pool is found, keep the unconditional WARN regarding
  the missing pool.
- If a pool was found but is exhausted, respect __GFP_NOWARN and update
  the warning message to explicitly state "DMA pool exhausted".

Fixes: 9420139f516d ("dma-pool: fix coherent pool allocations for IOMMU mappings")
Signed-off-by: Sai Sree Kartheek Adivi 
Reviewed-by: Robin Murphy 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20260128133554.3056582-1-s-adivi@ti.com
Signed-off-by: Sasha Levin

dma/pool: eliminate alloc_pages warning in atomic_pool_expand

2026-01-11T14:21:38+00:00

[ Upstream commit 463d439becb81383f3a5a5d840800131f265a09c ]

atomic_pool_expand iteratively tries the allocation while decrementing
the page order. There is no need to issue a warning if an attempted
allocation fails.

Signed-off-by: Dave Kleikamp 
Reviewed-by: Robin Murphy 
Fixes: d7e673ec2c8e ("dma-pool: Only allocate from CMA when in same memory zone")
[mszyprow: fixed typo]
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20251202152810.142370-1-dave.kleikamp@oracle.com
Signed-off-by: Sasha Levin

dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted

2025-09-04T13:30:27+00:00

commit 89a2d212bdb4bc29bed8e7077abe054b801137ea upstream.

When CONFIG_DMA_DIRECT_REMAP is enabled, atomic pool pages are
remapped via dma_common_contiguous_remap() using the supplied
pgprot. Currently, the mapping uses
pgprot_dmacoherent(PAGE_KERNEL), which leaves the memory encrypted
on systems with memory encryption enabled (e.g., ARM CCA Realms).

This can cause the DMA layer to fail or crash when accessing the
memory, as the underlying physical pages are not configured as
expected.

Fix this by requesting a decrypted mapping in the vmap() call:
pgprot_decrypted(pgprot_dmacoherent(PAGE_KERNEL))

This ensures that atomic pool memory is consistently mapped
unencrypted.

Cc: stable@vger.kernel.org
Signed-off-by: Shanker Donthineni 
Reviewed-by: Catalin Marinas 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20250811181759.998805-1-sdonthineni@nvidia.com
Signed-off-by: Greg Kroah-Hartman

dma-pool: remove a __maybe_unused label in atomic_pool_expand

2023-08-31T12:12:37+00:00

Move the #endif a line so that free_page label is only seen by the
compile pass when actually used.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Chunhui He 
Reviewed-by: Robin Murphy

mm, treewide: redefine MAX_ORDER sanely

2023-04-06T02:42:46+00:00

MAX_ORDER currently defined as number of orders page allocator supports:
user can ask buddy allocator for page order between 0 and MAX_ORDER-1.

This definition is counter-intuitive and lead to number of bugs all over
the kernel.

Change the definition of MAX_ORDER to be inclusive: the range of orders
user can ask from buddy allocator is 0..MAX_ORDER now.

[kirill@shutemov.name: fix min() warning]
  Link: https://lkml.kernel.org/r/20230315153800.32wib3n5rickolvh@box
[akpm@linux-foundation.org: fix another min_t warning]
[kirill@shutemov.name: fixups per Zi Yan]
  Link: https://lkml.kernel.org/r/20230316232144.b7ic4cif4kjiabws@box.shutemov.name
[akpm@linux-foundation.org: fix underlining in docs]
  Link: https://lore.kernel.org/oe-kbuild-all/202303191025.VRCTk6mP-lkp@intel.com/
Link: https://lkml.kernel.org/r/20230315113133.11326-11-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov 
Reviewed-by: Michael Ellerman 	[powerpc]
Cc: "Kirill A. Shutemov" 
Cc: Zi Yan 
Signed-off-by: Andrew Morton

dma/pool: create dma atomic pool only if dma zone has managed pages

2022-01-15T14:30:29+00:00

Currently three dma atomic pools are initialized as long as the relevant
kernel codes are built in.  While in kdump kernel of x86_64, this is not
right when trying to create atomic_pool_dma, because there's no managed
pages in DMA zone.  In the case, DMA zone only has low 1M memory
presented and locked down by memblock allocator.  So no pages are added
into buddy of DMA zone.  Please check commit f1d4d47c5851 ("x86/setup:
Always reserve the first 1M of RAM").

Then in kdump kernel of x86_64, it always prints below failure message:

 DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
 swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-0.rc5.20210611git929d931f2b40.42.fc35.x86_64 #1
 Hardware name: Dell Inc. PowerEdge R910/0P658H, BIOS 2.12.0 06/04/2018
 Call Trace:
  dump_stack+0x7f/0xa1
  warn_alloc.cold+0x72/0xd6
  __alloc_pages_slowpath.constprop.0+0xf29/0xf50
  __alloc_pages+0x24d/0x2c0
  alloc_page_interleave+0x13/0xb0
  atomic_pool_expand+0x118/0x210
  __dma_atomic_pool_init+0x45/0x93
  dma_atomic_pool_init+0xdb/0x176
  do_one_initcall+0x67/0x320
  kernel_init_freeable+0x290/0x2dc
  kernel_init+0xa/0x111
  ret_from_fork+0x22/0x30
 Mem-Info:
 ......
 DMA: failed to allocate 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation
 DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations

Here, let's check if DMA zone has managed pages, then create
atomic_pool_dma if yes.  Otherwise just skip it.

Link: https://lkml.kernel.org/r/20211223094435.248523-3-bhe@redhat.com
Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
Signed-off-by: Baoquan He 
Reviewed-by: Christoph Hellwig 
Acked-by: John Donnelly  
Reviewed-by: David Hildenbrand 
Cc: Marek Szyprowski 
Cc: Robin Murphy 
Cc: Borislav Petkov 
Cc: Christoph Lameter 
Cc: David Laight 
Cc: David Rientjes 
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim 
Cc: Pekka Enberg 
Cc: Vlastimil Babka 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

dma-pool: no need to check return value of debugfs_create functions

2020-11-27T09:33:42+00:00

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Signed-off-by: Tiezhu Yang 
Reviewed-by: Robin Murphy 
Signed-off-by: Christoph Hellwig

dma-mapping: merge into

2020-10-06T05:07:06+00:00

Move more nitty gritty DMA implementation details into the common
internal header.

Signed-off-by: Christoph Hellwig

dma-mapping: merge into

2020-10-06T05:07:04+00:00

Merge dma-contiguous.h into dma-map-ops.h, after removing the comment
describing the contiguous allocator into kernel/dma/contigous.c.

Signed-off-by: Christoph Hellwig

dma-direct: remove dma_direct_{alloc,free}_pages

2020-09-11T07:10:29+00:00

Just merge these helpers into the main dma_direct_{alloc,free} routines,
as the additional checks are always false for the two callers.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Robin Murphy