[PATCH RFC 00/13] fix DMA aligment issues around virtio

[Michael S. Tsirkin]

Cong Wang reported dma debug warnings with virtio-vsock
and proposed a patch, see:

https://lore.kernel.org/all/20251228015451.1253271-1-xiyou.wangcong@xxxxxxxxx/

however, the issue is more widespread.
This is an attempt to fix it systematically.
Note: i2c and gio might also be affected, I am still looking
into it. Help from maintainers welcome.

Early RFC, compile tested only. Sending for early feedback/flames.
Cursor/claude used liberally mostly for refactoring, and english.

DMA maintainers, could you please confirm the DMA core changes
are ok with you?

Thanks!


Michael S. Tsirkin (13):
  dma-mapping: add __dma_from_device_align_begin/end
  docs: dma-api: document __dma_align_begin/end
  dma-mapping: add DMA_ATTR_CPU_CACHE_CLEAN
  docs: dma-api: document DMA_ATTR_CPU_CACHE_CLEAN
  dma-debug: track cache clean flag in entries
  virtio: add virtqueue_add_inbuf_cache_clean API
  vsock/virtio: fix DMA alignment for event_list
  vsock/virtio: use virtqueue_add_inbuf_cache_clean for events
  virtio_input: fix DMA alignment for evts
  virtio_scsi: fix DMA cacheline issues for events
  virtio-rng: fix DMA alignment for data buffer
  virtio_input: use virtqueue_add_inbuf_cache_clean for events
  vsock/virtio: reorder fields to reduce struct padding

 Documentation/core-api/dma-api-howto.rst  | 42 +++++++++++++
 Documentation/core-api/dma-attributes.rst |  9 +++
 drivers/char/hw_random/virtio-rng.c       |  2 +
 drivers/scsi/virtio_scsi.c                | 18 ++++--
 drivers/virtio/virtio_input.c             |  5 +-
 drivers/virtio/virtio_ring.c              | 72 +++++++++++++++++------
 include/linux/dma-mapping.h               | 17 ++++++
 include/linux/virtio.h                    |  5 ++
 kernel/dma/debug.c                        | 26 ++++++--
 net/vmw_vsock/virtio_transport.c          |  8 ++-
 10 files changed, 172 insertions(+), 32 deletions(-)

-- 
MST