[virtio-dev] Re: [PATCH] Add virtio gpu driver.

[Michael S. Tsirkin]

On Thu, Mar 26, 2015 at 04:07:16PM +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> > I don't know. This seems exactly like the kind of thing
> > we had in mind when we added the virtio pci capability.
> > For example, we have text in spec that requires drivers
> > to skip unknown capabilities.
> > 
> > And yes, if bios pokes at a specific bar then we do
> > need to list this info in the virtio spec so this makes
> > it an issue that is virtio related.
> 
> Hmm, virtio-vga is a two-in-one device basically.  When virtio is
> enabled it behaves like virtio-gpu-pci, otherwise it behaves very
> simliar to stdvga.  So you need to know nothing about virtio to handle
> the vga side, and I want keep it that way.
> 
> When no vga compatibility is needed there always is the option to just
> use virtio-gpu-pci instead.
> 
> > Yes, it's not about what we put there now. It's about being able
> > to move things about in the future without breaking guests.
> 
> We don't have that today for stdvga, and I still fail to see what this
> buys us.
> 
> 
> Completely different thing crossing my mind:  I think we can make
> virtio-vga fully compatible with stdvga.  stdvga has two bars, memory
> (#0) and mmio (#2).  We can make the mmio bar larger and place all the
> virtio regions there.
> 

Full compatibility with some standard sounds like a better motivation,
yes.

> 
> I think in any case I'll go split off the vga compatibility bits to a
> different patch (and possible a separate patch series).
> 
> cheers,
>   Gerd

Will you still need me to change core to claim specific memory only?


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MST