Re: [Xen-devel] [v2][PATCH] xen/vtd/iommu: permit group devices to passthrough in relaxed mode

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

> > > > Need to have separate warning/error level for relax/strict.
> > > >
> > > > However I don't think this patch is a right fix. So far relax/strict policy
> > > > is per-domain. what about one VM specifies relax while another VM
> > > > specifies strict when each is assigned with a device sharing rmrr
> > > > with the other? In that case it becomes a system-wide security hole.
> > >
> > > The one specifying "strict" won't gets its device assigned (due to
> > > the code above, taking the path that was there already without
> > > the patch), so I don't see the security issue.
> > >
> >
> > Agreed. A VM can't get such device assigned in the first place, so the
> > hypothetical scenario doesn't exist.
> Sorry it's a bad example. My actual concern is that we can't count
> on this per-VM relax/strict policy to prevent group devices assigned
> to different VM. In that case it's definitely a security hole since
> one VM may clobber shared RMRR to impact another VM. So right
> example for that scenario is both VMs specified with 'relax'.
What if one of group devices is still owned by Dom0?

Thanks
Tiejun

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