Re: [Qemu-devel] [PATCH 00/35] Alpha system emulation, v4

[Paul Brook]

> On 05/10/2011 02:33 PM, Paul Brook wrote:
> > There should be nothing special about virtio-pci. These devices should
> > access memory in exactly the same way as any other PCI device. Bypassing
> > the normal PCI iommu is IMO a serious bug.
> 
> I suspect that the argument is that virtio is implemented on several
> busses, and ignoring any bus-specific stuff means that there's less
> need for any code differences.

It also has some horrifically bad implications. Not least of which is the 
inability to sanely handle nested virtualization.

IMO the whole point of virtio-pci is that it avoids magical weirdness for 
virtio devices devices.  If you're going to start adding nonstandard 
exceptions for virtio devices than there seem little point using PCI in the 
first place.  It's likely to cause more problems than it solves for the guest 
drivers.

Paul