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

Jerry Snitselaar
2023-10-02T07:51:19Z

On Mon, Oct 02, 2023 at 08:04:24AM +0200, Christoph Hellwig wrote:
> On Sun, Oct 01, 2023 at 07:22:36AM -0700, Jerry Snitselaar wrote:
> > Changes last year to the dma-mapping api to no longer allow __GFP_COMP,
> > in particular these two (from the e529d3507a93 dma-mapping pull for
> > 6.2):
>
> That's complete BS. The driver was broken since day 1 and always
> ignored the DMA API requirement to never try to grab the page from the
> dma coherent allocation because you generally speaking can't. It just
> happened to accidentally work the trivial dma coherent allocator that
> is used on x86.
>

re-sending since gmail decided to not send plain text:

Yes, I agree that it has been broken and misusing the API. Greg's
question was what changed though, and it was the clean up of
__GFP_COMP in dma-mapping that brought the problem in the driver to
light.

I already said the other day that cnic has been doing this for 14
years. I'm not blaming you or your __GFP_COMP cleanup commits, they
just uncovered that cnic was doing something wrong. My apologies if
you took it that way.

Regards,
Jerry