Re: [RFC 00/18] vfio: Adopt iommufd

[Nicolin Chen <nicolinc@nvidia.com>]

On Sun, Apr 17, 2022 at 12:30:40PM +0200, Eric Auger wrote:

> >> - More tests
> > I did a quick test on my ARM64 platform, using "iommu=smmuv3"
> > string. The behaviors are different between using default and
> > using legacy "iommufd=off".
> >
> > The legacy pathway exits the VM with:
> >     vfio 0002:01:00.0:
> >     failed to setup container for group 1:
> >     memory listener initialization failed:
> >     Region smmuv3-iommu-memory-region-16-0:
> >     device 00.02.0 requires iommu MAP notifier which is not currently supported
> >
> > while the iommufd pathway started the VM but reported errors
> > from host kernel about address translation failures, probably
> > because of accessing unmapped addresses.
> >
> > I found iommufd pathway also calls error_propagate_prepend()
> > to add to errp for not supporting IOMMU_NOTIFIER_MAP, but it
> > doesn't get a chance to print errp out. Perhaps there should
> > be a final error check somewhere to exit?
> 
> thank you for giving it a try.
> 
> vsmmuv3 + vfio is not supported as we miss the HW nested stage support
> and SMMU does not support cache mode. If you want to test viommu on ARM
> you shall test virtio-iommu+vfio. This should work but this is not yet
> tested.

I tried "-device virtio-iommu" and "-device virtio-iommu-pci"
separately with vfio-pci, but neither seems to work. The host
SMMU driver reports Translation Faults.

Do you know what commands I should use to run QEMU for that
combination?

> I pushed a fix for the error notification issue:
> qemu-for-5.17-rc6-vm-rfcv2-rc0 on my git https://github.com/eauger/qemu.git

Yes. This fixes the problem. Thanks!