Re: [RFC PATCH 0/5] hw/arm/virt: Add support for user-creatable nested SMMUv3

["Daniel P. Berrangé" <berrange@redhat.com>]

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.

With regards,
Daniel
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