On Thu, Feb 06, 2025 at 01:46:47PM -0400, Jason Gunthorpe wrote:
> On Thu, Feb 06, 2025 at 05:10:32PM +0000, Daniel P. Berrangé wrote:
> > On Thu, Feb 06, 2025 at 01:02:38PM -0400, Jason Gunthorpe wrote:
> > > On Thu, Feb 06, 2025 at 03:07:06PM +0000, Shameerali Kolothum Thodi wrote:
> > > > > If we set the physical/guest SMMU relationship directly, then at the
> > > > > time the VFIO device is plugged, we can diagnose the incorrectly
> > > > > placed VFIO device, and better reason about behaviour.
> > > > 
> > > > Agree.
> > > 
> > > Can you just take in a VFIO cdev FD reference on this command line:
> > > 
> > >  -device arm-smmuv3-accel,id=smmuv2,bus=pcie.2
> > > 
> > > And that will lock the pSMMU/vSMMU relationship?
> > 
> > We shouldn't assume any VFIO device exists in the QEMU cnofig at the time
> > we realize the virtual ssmu. I expect the SMMU may be cold plugged, while
> > the VFIO devices may be hot plugged arbitrarly later, and we should have
> > the association initialized the SMMU is realized.
> 
> This is not supported kernel side, you can't instantiate a vIOMMU
> without a VFIO device that uses it. For security.

What are the security concerns here ?

With regards,
Daniel
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