linux-kernel - Re: [PATCH] Changing the AMD IOMMU API path to work in an atomic context which is necessary for any custom drivers using the IOMMU API while holding a spinlock.

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Message-ID: <20180827070731.GA8588@infradead.org>
Date:   Mon, 27 Aug 2018 00:07:31 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Tom Murphy <murphyt7@....ie>
Cc:     Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@...radead.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Changing the AMD IOMMU API path to work in an atomic
 context which is necessary for any custom drivers using the IOMMU API while
 holding a spinlock.

On Fri, Aug 24, 2018 at 11:55:53PM +0100, Tom Murphy wrote:
> We were going to do this by using the iommu-dma api and replacing all the
> existing calls to the DMA api functions in the amd driver with their
> iommu-dma equivalent like in this driver:
> https://elixir.bootlin.com/linux/latest/source/arch/arm64/mm/dma-mapping.c#L810

FYI, I have a a wip branch to move the arm64 wrappers for both
swiotlb and dma-iommu here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-maybe-coherent

Maybe you could try to base on top of that.

> To do this we need the map/unmap callbacks to be spinlock-safe.

You probably want to send the patch together with the one(s) making use
of it.