linux-kernel - Re: [PATCH] dma-direct: Set SG_DMA

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Message-ID: <20240508113353.GA31529@lst.de>
Date: Wed, 8 May 2024 13:33:53 +0200
From: Christoph Hellwig <hch@....de>
To: "T.J. Mercier" <tjmercier@...gle.com>
Cc: Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>, isaacmanjarres@...gle.com,
	Catalin Marinas <catalin.marinas@....com>, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma-direct: Set SG_DMA_SWIOTLB flag for dma-direct

On Tue, May 07, 2024 at 01:07:25PM -0700, T.J. Mercier wrote:
> On Mon, May 6, 2024 at 10:43???PM Christoph Hellwig <hch@....de> wrote:
> >
> > On Mon, May 06, 2024 at 09:39:53AM -0700, T.J. Mercier wrote:
> > > > You should not check, you simply must handle it by doing the proper
> > > > DMA API based ownership management.
> > >
> > > That doesn't really work for uncached buffers.
> >
> > What uncached buffers?
> 
> For example these ones:
> https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/drivers/dma-buf/heaps/system_heap.c#141

Whatever that code is doing is probably not upstream because it's too
broken to live.