Re: [PATCH v5 0/4] UIO_MEM_DMA_COHERENT for cnic/bnx2/bnx2x

[Chris Leech]

I think all the feedback on these has been addressed, so I'm asking
once more if these UIO additions can be considered for inclusion.

Thanks,
- Chris

On Thu, Feb 1, 2024 at 3:34 PM Chris Leech <cleech@xxxxxxxxxx> wrote:
>
> 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.
>
> The cnic uio interface also has issues running with an iommu enabled,
> which these changes correct.
>
> In order to fix these drivers to be able to mmap dma coherent memory via
> a uio device, introduce a new uio mmap type backed by dma_mmap_coherent.
>
> While I understand some complaints about how these drivers have been
> structured, I also don't like letting support bitrot when there's a
> reasonable alternative to re-architecting an existing driver. I believe
> this to be the most sane way to restore these drivers to functioning
> properly.
>
> There are two other uio drivers which are mmaping dma_alloc_coherent
> memory as UIO_MEM_PHYS, uio_dmem_genirq and uio_pruss.
> These drivers are converted in the later patches of this series.
>
> v5:
> - convert uio_pruss and uio_dmem_genirq
> - added dev_warn and comment about not adding more users
> - put some PAGE_ALIGNs back in cnic to keep checks in
>   uio_mmap_dma_coherent matched with uio_mmap_physical.
> - dropped the Fixes trailer
> v4:
> - re-introduce the dma_device member to uio_map,
>   it needs to be passed to dma_mmap_coherent somehow
> - drop patch 3 to focus only on the uio interface,
>   explicit page alignment isn't needed
> - re-add the v1 mail recipients,
>   this isn't something to be handled through linux-scsi
> v3 (Nilesh Javali <njavali@xxxxxxxxxxx>):
> - fix warnings reported by kernel test robot
>   and added base commit
> v2 (Nilesh Javali <njavali@xxxxxxxxxxx>):
> - expose only the dma_addr within uio and cnic.
> - Cleanup newly added unions comprising virtual_addr
>   and struct device
>
> previous threads:
> v1: https://lore.kernel.org/all/20230929170023.1020032-1-cleech@xxxxxxxxxx/
> attempt at an alternative change: https://lore.kernel.org/all/20231219055514.12324-1-njavali@xxxxxxxxxxx/
> v2: https://lore.kernel.org/all/20240103091137.27142-1-njavali@xxxxxxxxxxx/
> v3: https://lore.kernel.org/all/20240109121458.26475-1-njavali@xxxxxxxxxxx/
> v4: https://lore.kernel.org/all/20240131191732.3247996-1-cleech@xxxxxxxxxx/
>
> Chris Leech (4):
>   uio: introduce UIO_MEM_DMA_COHERENT type
>   cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT
>   uio_pruss: UIO_MEM_DMA_COHERENT conversion
>   uio_dmem_genirq: UIO_MEM_DMA_COHERENT conversion
>
>  drivers/net/ethernet/broadcom/bnx2.c          |  1 +
>  .../net/ethernet/broadcom/bnx2x/bnx2x_main.c  |  2 +
>  drivers/net/ethernet/broadcom/cnic.c          | 25 ++++++----
>  drivers/net/ethernet/broadcom/cnic.h          |  1 +
>  drivers/net/ethernet/broadcom/cnic_if.h       |  1 +
>  drivers/uio/uio.c                             | 47 +++++++++++++++++++
>  drivers/uio/uio_dmem_genirq.c                 | 22 ++++-----
>  drivers/uio/uio_pruss.c                       |  6 ++-
>  include/linux/uio_driver.h                    |  8 ++++
>  9 files changed, 89 insertions(+), 24 deletions(-)
>
>
> base-commit: 861c0981648f5b64c86fd028ee622096eb7af05a
> --
> 2.43.0
>