Re: [Xen-devel] [PATCH] drm/xen-front: Make shmem backed display buffer coherent

[Daniel Vetter <daniel@xxxxxxxx>]

On Thu, Dec 20, 2018 at 7:33 PM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>
> On Thu, Dec 20, 2018 at 07:29:37PM +0100, Daniel Vetter wrote:
> > What we most definitely not want to end up with though is actually
> > streaming dma, because with that all the zero copy buffer sharing
> > tricks become pointless. There's pretty epic amounts of hacks to work
> > around this, I have no idea what's supposed to give here.
>
> Err, with streaming DMA buffer sharing is trivial.  The coherent DMA
> allocator is what causes all kinds of horrible hacks that can't actually
> work on various platforms.

Hm, I thought the streaming dma api is the one that causes bounce
buffers and all that fun. If you're unlucky at least.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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