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: <20180827065841.GA7053@infradead.org>
Date:   Sun, 26 Aug 2018 23:58:41 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Christoph Hellwig <hch@...radead.org>, murphyt7@....ie,
        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 04:24:49PM +0100, Robin Murphy wrote:
> Although IIRC the AMD driver is in fact the only one whose map/unmap
> callbacks aren't already spinlock-safe (or at least it was last time I was
> looking). Stuff like iommu-dma is already relying on this in order to
> implement streaming DMA API calls (which may be in atomic context) on top of
> the corresponding IOMMU API operations.

True.  That should be mentioned in the spinlock, though - and once
it is done the calling conventions should be documented.