Re: [virtio-dev] Memory sharing device

From
Dr. David Alan Gilbert <>
Date
2019-02-21T10:03:55+00:00
ID
20190221100330.GC2605@work-vm
Thread
Re: [virtio-dev] Memory sharing device
* Gerd Hoffmann () wrote:
>   Hi,
> 
> > > Note:  I think using a pci memory bar (aka host memory mapped into the
> > > guest) as backing storage for dma-bufs isn't going to work.
> > 
> > (Not knowing dma-bufs) but could you explain why?
> 
> Many places in the linux kernel assume dma-bufs are built out of normal
> ram pages (i.e. something backed by struct page).  Which is not the case
> for pci memory bars which are typically ioremapped() (completely or in
> chunks) to access them.

Ah OK, so it's the view from inside the guest that's the problem.

Dave


> cheers,
>   Gerd
> 
> 
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--
Dr. David Alan Gilbert /  / Manchester, UK