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Draft: UIO_MEM_DMA_COHERENT for cnic/bnx2/bnx2x

Nilesh Javali requested to merge njavali/centos-stream-9:RHEL-18335 into main

JIRA: https://issues.redhat.com/browse/RHEL-18335

Upstream Status: RHEL-only

During bnx2i iSCSI testing we ran into page refcounting issues in the uio mmaps exported from cnic to the iscsiuio process, and bisected back to the removal of the __GFP_COMP flag from dma_alloc_coherent calls.

In order to fix these drivers to be able to mmap dma coherent memory via a uio device, without resorting to hacks and working with an iommu enabled, introduce a new uio mmap type backed by dma_mmap_coherent.

While converting the uio interface, I also noticed that not all of these allocations were PAGE_SIZE aligned. Particularly the bnx2/bnx2x status block mapping was much smaller than any architecture page size, and I was concerned that it could be unintentionally exposing kernel memory.

v3:

  • fix warnings reported by kernel test robot and added base commit v2:
  • expose only the dma_addr within uio and cnic.
  • Cleanup newly added unions comprising virtual_addr and struct device

Chris Leech (3): uio: introduce UIO_MEM_DMA_COHERENT type cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT cnic,bnx2,bnx2x: page align uio mmap allocations

drivers/net/ethernet/broadcom/bnx2.c | 2 + .../net/ethernet/broadcom/bnx2x/bnx2x_main.c | 10 +++-- drivers/net/ethernet/broadcom/cnic.c | 20 +++++++--- drivers/net/ethernet/broadcom/cnic.h | 1 + drivers/net/ethernet/broadcom/cnic_if.h | 1 + drivers/uio/uio.c | 40 +++++++++++++++++++ include/linux/uio_driver.h | 2 + 7 files changed, 66 insertions(+), 10 deletions(-)

base-commit: ed340d13aa1db6773667ed4bf907738df203fbda

dma-mapping: reject _GFP_COMP in dma_alloc_attrs cnic: don't pass bogus GFP flags to dma_alloc_coherent

Signed-off-by: Nilesh Javali njavali@redhat.com

Edited by Nilesh Javali

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