Re: [virtio-dev] Memory sharing device

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Gerd Hoffmann (kraxel@redhat.com) 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 / dgilbert@redhat.com / Manchester, UK