Re: [PATCH 2/2] cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT

[Greg Kroah-Hartman]

On Wed, Jan 31, 2024 at 11:17:32AM -0800, Chris Leech wrote:
> Use the UIO_MEM_DMA_COHERENT type to properly handle mmap for
> dma_alloc_coherent buffers.
> 
> The cnic l2_ring and l2_buf mmaps have caused page refcount issues as
> the dma_alloc_coherent no longer provide __GFP_COMP allocation as per
> commit "dma-mapping: reject __GFP_COMP in dma_alloc_attrs".
> 
> Fix this by having the uio device use dma_mmap_coherent.
> 
> The bnx2 and bnx2x status block allocations are also dma_alloc_coherent,
> and should use dma_mmap_coherent. They don't allocate multiple pages,
> but this interface does not work correctly with an iommu enabled unless
> dma_mmap_coherent is used.
> 
> Fixes: bb73955c0b1d ("cnic: don't pass bogus GFP_ flags to dma_alloc_coherent")

This is really the commit that broke things?  By adding this, are you
expecting anyone to backport this change to older kernels?

thanks,

greg k-h