Re: [PATCH 3/3] cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT

Chris Leech
2023-09-30T18:20:17Z

On Sat, Sep 30, 2023 at 09:06:51AM +0200, Greg Kroah-Hartman wrote:
> On Fri, Sep 29, 2023 at 10:00:23AM -0700, Chris Leech wrote:
> > Make use of the new UIO_MEM_DMA_COHERENT type to properly handle mmap
> > for dma_alloc_coherent buffers.
>
> Why are ethernet drivers messing around with UIO devices? That's not
> what UIO is for, unless you are trying to do kernel bypass for these
> devices without anyone noticing?
>
> confused,

It's confusing. The bnx2 driver stack included a cnic (converged nic?)
module that sits between the ethernet drivers (bnx2, bnx2x) and protocol
offload drivers (iscsi, fcoe, rdma).

The iscsi module (bnx2i) uses a passthrough interface from cnic to
handle some network configuration that the device firmware doesn't do.
It uses a uio device and a userspace component called iscsiuio to do
that.

Questions beyond that will probably need to be answer by one of the many
Marvell engineers copied on this thread.

- Chris