[Qemu-devel] Re: [PATCH] Inter-VM shared memory PCI device

[Arnd Bergmann]

On Thursday 11 March 2010, Avi Kivity wrote:
> > A totally different option that avoids this whole problem would
> > be to separate the signalling from the shared memory, making the
> > PCI shared memory device a trivial device with a single memory BAR,
> > and using something a higher-level concept like a virtio based
> > serial line for the actual signalling.
> >    
> 
> That would be much slower.  The current scheme allows for an 
> ioeventfd/irqfd short circuit which allows one guest to interrupt 
> another without involving their qemus at all.

Yes, the serial line approach would be much slower, but my point
was that we can do signaling over "something else", which could
well be something building on irqfd.

        Arnd