linux-kernel - Re: clearly mark DMA_OPS support as an architecture feasture

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Message-ID: <CACGkMEsK8k=yX2ZytMJQhdZi4PS9-7KLUYmf2oGLu-UvNEYzug@mail.gmail.com>
Date: Mon, 26 Aug 2024 14:16:36 +0800
From: Jason Wang <jasowang@...hat.com>
To: Christoph Hellwig <hch@....de>
Cc: iommu@...ts.linux.dev, Marek Szyprowski <m.szyprowski@...sung.com>, 
	Robin Murphy <robin.murphy@....com>, Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Bingbu Cao <bingbu.cao@...el.com>, "Michael S . Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org, 
	linux-alpha@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org, 
	sparclinux@...r.kernel.org, linux-media@...r.kernel.org, 
	virtualization@...ts.linux.dev, xen-devel@...ts.xenproject.org
Subject: Re: clearly mark DMA_OPS support as an architecture feasture

On Sat, Aug 24, 2024 at 11:58 AM Christoph Hellwig <hch@....de> wrote:
>
> Hi all,
>
> we've had a long standing problems where drivers try to hook into the
> DMA_OPS mechanisms to override them for something that is not DMA, or
> to introduce additional dispatching.
>
> Now that we are not using DMA_OPS support for dma-iommu and can build
> kernels without DMA_OPS support on many common setups this becomes even
> more problematic.
>
> This series renames the option to ARCH_DMA_OPS and adds very explicit
> comment to not use it in drivers.  The ipu6 and vdpa_sim/user drivers
> that abuse the mechanism are made to depend on the option instead of
> selecting it with a big comment, but I expect this to be fixed rather
> sooner than later (I know the ipu6 maintainers are on it based on a
> previous discussion).
>

I will try to fix the simulator considering virtio has already had
mapping ops now.

Thanks