On Thu, Aug 24, 2017 at 02:10:34PM +0200, Paolo Bonzini wrote:
> On 24/08/2017 13:53, Tiwei Bie wrote:
> >
> > * In addition to the DESC_HW flag, each virtio queue has a tail pointer
> > - Driver creates suitable (i.e. multiple of cacheline) descriptors,
> > then performs MMIO write to tail pointer.
>
> If I understand correctly, the tail pointer is the value that is written
> to the MMIO register. If that is the case, this is unfortunately bad
> for virtualization. Virt prefers a doorbell register where the value
> doesn't matter.
I think it's fine actually, this tail pointer merely duplicates data
that is already available in form of DESC_HW flag. Virt can just ignore
the value.
