Re: [Qemu-devel] [PATCH] all vga: refuse hotplugging.

[Stefano Stabellini]

On Wed, 26 May 2010, Gerd Hoffmann wrote:
> On 05/26/10 12:59, Stefano Stabellini wrote:
> > On Wed, 26 May 2010, Gerd Hoffmann wrote:
> >> Try to pci hotplug a vga card, watch qemu die with hw_error().
> >> This patch fixes it.
> >>
> >
> > Do you know the reason why we get hw_error()?
> 
> Because the card tries to register the legacy vga ports which are 
> already taken by the primary card.  I also don't know whenever you can 
> pci hot-plug hardware which uses non-pci ressources at all.
> 
> > Theoretically vga hotplug should be possible at least for secondary
> > graphic cards (even though I suspect most operating systems wouldn't
> > cope).
> 
> Yes.  Assuming the virtual hardware in question can actually act as 
> secondary, i.e. is fully programmable without the legacy vga ports.  The 
> standard vga can't.  The cirrus looks doable, at least you can access 
> the vga ports using the mmio bar.
 
I see, good point.

I guess the right fix here would be to return -1 in the stdvga case but
continue in the cirrus case and avoid registering the vga ioports when
used as secondary adapter.