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Message-ID: <2554ed057e08e66dd110c3e09a27378b9a06bdd6.camel@redhat.com> Date: Thu, 05 Oct 2023 12:39:05 +0200 From: Paolo Abeni <pabeni@...hat.com> To: Hannes Reinecke <hare@...e.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jerry Snitselaar <jsnitsel@...hat.com> Cc: Christoph Hellwig <hch@....de>, Chris Leech <cleech@...hat.com>, Rasesh Mody <rmody@...vell.com>, Ariel Elior <aelior@...vell.com>, Sudarsana Kalluru <skalluru@...vell.com>, Manish Chopra <manishc@...vell.com>, Nilesh Javali <njavali@...vell.com>, Manish Rangankar <mrangankar@...vell.com>, John Meneghini <jmeneghi@...hat.com>, Lee Duncan <lduncan@...e.com>, Mike Christie <michael.christie@...cle.com>, Hannes Reinecke <hare@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/3] cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT On Mon, 2023-10-02 at 10:59 +0200, Hannes Reinecke wrote: > On 10/2/23 10:46, Greg Kroah-Hartman wrote: > > On Mon, Oct 02, 2023 at 12:50:21AM -0700, Jerry Snitselaar wrote: > > > 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. > > > > As these devices aren't being made anymore, and this api is really not a > > good idea in the first place, why don't we just leave it broken and see > > if anyone notices? > > > Guess what triggered this mail thread. > Some customers did notice. > > Problem is that these devices were built as the network interface in > some bladecenter machines, so you can't just replace them with a > different Ethernet card. This route looks a no-go. Out of sheer ignorance, would the iommu hack hinted in the cover letter require similar controversial changes? Cheers, Paolo
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