Re: [RFC PATCH] iommu/arm-smmu-v3: Allow nested attach for PCI bridges without vDEVICE

[Jason Gunthorpe]

On Fri, Aug 14, 2026 at 06:56:05PM +0000, Dmitry Malkin wrote:
> Hi Jason,
> 
> > If viommu should support multi-device groups, I'm not sure. I want to
> > know why you even have multi-device groups in the first place because
> > that is not normal at all.
> 
> That is because of the 'pci=config_acs' kernel command-line
> parameter. This causes the kernel to create a single IOMMU group
> containing multiple PCIe devices, including the bridge (PCIe Root
> Port).

Don't use it that way?

If this is an nvidia system you should talk to your support team.

Jason