Re: [Xen-devel] [Hackathon minutes] PV network improvements

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, May 21, 2013 at 11:01:51AM +0100, George Dunlap wrote:
> On Tue, May 21, 2013 at 10:26 AM, Tim Deegan <tim@xxxxxxx> wrote:
> > At 19:31 +0100 on 20 May (1369078279), Wei Liu wrote:
> >> On Mon, May 20, 2013 at 03:08:05PM +0100, Stefano Stabellini wrote:
> >> > J) Map the whole physical memory of the machine in dom0
> >> > If mapping/unmapping or copying slows us down, could we just keep the
> >> > whole physical memory of the machine mapped in dom0 (with corresponding
> >> > IOMMU entries)?
> >> > At that point the frontend could just pass mfn numbers to the backend,
> >> > and the backend would already have them mapped.
> >> > >From a security perspective it doesn't change anything when running
> >> > the backend in dom0, because dom0 is already capable of mapping random
> >> > pages of any guests. QEMU instances do that all the time.
> >> > But it would take away one of the benefits of deploying driver domains:
> >> > we wouldn't be able to run the backends at a lower privilege level.
> >> > However it might still be worth considering as an option? The backend is
> >> > still trusted and protected from the frontend, but the frontend wouldn't
> >> > be protected from the backend.
> >> >
> >>
> >> I think Dom0 mapping all machine memory is a good starting point.
> >
> > I _strongly_ disagree.  The opportunity for disaggregation and reduction
> > of privilege in backends is probably Xen's biggest techical advantage
> > and we should not be taking any backward steps there.
> 
> I think Wei meant, "A good point to start the investigation".  If

Yes that's what I meant. :-)


Wei.

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