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Date:   Mon, 2 Oct 2023 00:50:21 -0700
From:   Jerry Snitselaar <jsnitsel@redhat.com>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Hannes Reinecke <hare@suse.de>,
        Chris Leech <cleech@redhat.com>,
        Rasesh Mody <rmody@marvell.com>,
        Ariel Elior <aelior@marvell.com>,
        Sudarsana Kalluru <skalluru@marvell.com>,
        Manish Chopra <manishc@marvell.com>,
        Nilesh Javali <njavali@marvell.com>,
        Manish Rangankar <mrangankar@marvell.com>,
        John Meneghini <jmeneghi@redhat.com>,
        Lee Duncan <lduncan@suse.com>,
        Mike Christie <michael.christie@oracle.com>,
        Hannes Reinecke <hare@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT
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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