linux-toradex.git/kernel/dma, branch v6.16-rc4

Merge tag 'dma-mapping-6.16-2025-05-26' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux

2025-05-28T03:09:06+00:00

Pull dma-mapping updates from Marek Szyprowski:
 "New two step DMA mapping API, which is is a first step to a long path
  to provide alternatives to scatterlist and to remove hacks, abuses and
  design mistakes related to scatterlists.

  This new approach optimizes some calls to DMA-IOMMU layer and cache
  maintenance by batching them, reduces memory usage as it is no need to
  store mapped DMA addresses to unmap them, and reduces some function
  call overhead.  It is a combination effort of many people, lead and
  developed by Christoph Hellwig and Leon Romanovsky"

* tag 'dma-mapping-6.16-2025-05-26' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux:
  docs: core-api: document the IOVA-based API
  dma-mapping: add a dma_need_unmap helper
  dma-mapping: Implement link/unlink ranges API
  iommu/dma: Factor out a iommu_dma_map_swiotlb helper
  dma-mapping: Provide an interface to allow allocate IOVA
  iommu: add kernel-doc for iommu_unmap_fast
  iommu: generalize the batched sync after map interface
  dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h
  PCI/P2PDMA: Refactor the p2pdma mapping helpers

dma-mapping: add a dma_need_unmap helper

2025-05-06T06:36:53+00:00

Add helper that allows a driver to skip calling dma_unmap_*
if the DMA layer can guarantee that they are no-nops.

Signed-off-by: Christoph Hellwig 
Tested-by: Jens Axboe 
Reviewed-by: Luis Chamberlain 
Signed-off-by: Leon Romanovsky 
Signed-off-by: Marek Szyprowski

dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h

2025-05-06T06:36:53+00:00

To support the upcoming non-scatterlist mapping helpers, we need to go
back to have them called outside of the DMA API.  Thus move them out of
dma-map-ops.h, which is only for DMA API implementations to pci-p2pdma.h,
which is for driver use.

Note that the core helper is still not exported as the mapping is
expected to be done only by very highlevel subsystem code at least for
now.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Logan Gunthorpe 
Acked-by: Bjorn Helgaas 
Tested-by: Jens Axboe 
Reviewed-by: Luis Chamberlain 
Reviewed-by: Lu Baolu 
Signed-off-by: Leon Romanovsky 
Signed-off-by: Marek Szyprowski

PCI/P2PDMA: Refactor the p2pdma mapping helpers

2025-05-06T06:36:53+00:00

The current scheme with a single helper to determine the P2P status
and map a scatterlist segment force users to always use the map_sg
helper to DMA map, which we're trying to get away from because they
are very cache inefficient.

Refactor the code so that there is a single helper that checks the P2P
state for a page, including the result that it is not a P2P page to
simplify the callers, and a second one to perform the address translation
for a bus mapped P2P transfer that does not depend on the scatterlist
structure.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Logan Gunthorpe 
Acked-by: Bjorn Helgaas 
Tested-by: Jens Axboe 
Reviewed-by: Luis Chamberlain 
Reviewed-by: Lu Baolu 
Signed-off-by: Leon Romanovsky 
Signed-off-by: Marek Szyprowski

dma-coherent: Warn if OF reserved memory is beyond current coherent DMA mask

2025-04-22T15:44:09+00:00

When a reserved memory region described in the device tree is attached
to a device, it is expected that the device's limitations are correctly
included in that description.

However, if the device driver failed to implement DMA address masking
or addressing beyond the default 32 bits (on arm64), then bad things
could happen because the DMA address was truncated, such as playing
back audio with no actual audio coming out, or DMA overwriting random
blocks of kernel memory.

Check against the coherent DMA mask when the memory regions are attached
to the device. Give a warning when the memory region can not be covered
by the mask.

A warning instead of a hard error was chosen, because it is possible
that existing drivers could be working fine even if they forgot to
extend the coherent DMA mask.

Signed-off-by: Chen-Yu Tsai 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20250421083930.374173-1-wenst@chromium.org

dma-mapping: Fix warning reported for missing prototype

2025-04-22T13:06:33+00:00

lkp reported a warning about missing prototype for a recent patch.

The kernel-doc style comments are out of sync, move them to the right
function.

Cc: Marek Szyprowski 
Cc: Christoph Hellwig 

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202504190615.g9fANxHw-lkp@intel.com/

Signed-off-by: Balbir Singh 
[mszyprow: reformatted subject]
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20250422114034.3535515-1-balbirs@nvidia.com

dma/mapping.c: dev_dbg support for dma_addressing_limited

2025-04-14T14:10:50+00:00

In the debug and resolution of an issue involving forced use of bounce
buffers, 7170130e4c72 ("x86/mm/init: Handle the special case of device
private pages in add_pages(), to not increase max_pfn and trigger
dma_addressing_limited() bounce buffers"). It would have been easier
to debug the issue if dma_addressing_limited() had debug information
about the device not being able to address all of memory and thus forcing
all accesses through a bounce buffer. Please see[2]

Implement dev_dbg to debug the potential use of bounce buffers
when we hit the condition. When swiotlb is used,
dma_addressing_limited() is used to determine the size of maximum dma
buffer size in dma_direct_max_mapping_size(). The debug prints could be
triggered in that check as well (when enabled).

Link: https://lore.kernel.org/lkml/20250401000752.249348-1-balbirs@nvidia.com/ [1]
Link: https://lore.kernel.org/lkml/20250310112206.4168-1-spasswolf@web.de/ [2]

Cc: Marek Szyprowski 
Cc: Robin Murphy 
Cc: "Christian König" 
Cc: Ingo Molnar 
Cc: Kees Cook 
Cc: Bjorn Helgaas 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Alex Deucher 
Cc: Bert Karwatzki 
Cc: Christoph Hellwig 

Signed-off-by: Balbir Singh 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20250414113752.3298276-1-balbirs@nvidia.com

dma/contiguous: avoid warning about unused size_bytes

2025-04-09T15:28:53+00:00

When building with W=1, this variable is unused for configs with
CONFIG_CMA_SIZE_SEL_PERCENTAGE=y:

kernel/dma/contiguous.c:67:26: error: 'size_bytes' defined but not used [-Werror=unused-const-variable=]

Change this to a macro to avoid the warning.

Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator")
Signed-off-by: Arnd Bergmann 
Signed-off-by: Marek Szyprowski 
Link: https://lore.kernel.org/r/20250409151557.3890443-1-arnd@kernel.org

dma-mapping: fix missing clear bdr in check_ram_in_range_map()

2025-03-12T12:41:44+00:00

As discussed in [1], if 'bdr' is set once, it would never get
cleared, hence 0 is always returned.

Refactor the range check hunk into a new helper dma_find_range(),
which allows 'bdr' to be cleared in each iteration.

Link: https://lore.kernel.org/all/64931fac-085b-4ff3-9314-84bac2fa9bdb@quicinc.com/ # [1]
Fixes: a409d9600959 ("dma-mapping: fix dma_addressing_limited() if dma_range_map can't cover all system RAM")
Suggested-by: Christoph Hellwig 
Signed-off-by: Baochen Qiang 
Link: https://lore.kernel.org/r/20250307030350.69144-1-quic_bqiang@quicinc.com
Signed-off-by: Marek Szyprowski

dma-debug: fix physical address calculation for struct dma_debug_entry

2024-11-28T09:19:16+00:00

Offset into the page should also be considered while calculating a physical
address for struct dma_debug_entry. page_to_phys() just shifts the value
PAGE_SHIFT bits to the left so offset part is zero-filled.

An example (wrong) debug assertion failure with CONFIG_DMA_API_DEBUG
enabled which is observed during systemd boot process after recent
dma-debug changes:

DMA-API: e1000 0000:00:03.0: cacheline tracking EEXIST, overlapping mappings aren't supported
WARNING: CPU: 4 PID: 941 at kernel/dma/debug.c:596 add_dma_entry
CPU: 4 UID: 0 PID: 941 Comm: ip Not tainted 6.12.0+ #288
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:add_dma_entry kernel/dma/debug.c:596
Call Trace:
 
debug_dma_map_page kernel/dma/debug.c:1236
dma_map_page_attrs kernel/dma/mapping.c:179
e1000_alloc_rx_buffers drivers/net/ethernet/intel/e1000/e1000_main.c:4616
...

Found by Linux Verification Center (linuxtesting.org).

Fixes: 9d4f645a1fd4 ("dma-debug: store a phys_addr_t in struct dma_debug_entry")
Signed-off-by: Fedor Pchelkin 
[hch: added a little helper to clean up the code]
Signed-off-by: Christoph Hellwig