Re: [PATCH v6 08/25] KVM: arm64: iommu: Shadow host stage-2 page table

Jason Gunthorpe
2026-05-01T13:00:17Z

On Fri, May 01, 2026 at 11:19:10AM +0000, Mostafa Saleh wrote:
> Create a page-table for the IOMMU that shadows the host CPU stage-2
> to establish DMA isolation.

Is there a reason you can't just use the CPU S2 for the iommu?

ie the CCA RMM is doing that, it is how ARM imagined this stuff would
work.

Once you start supporting DMA like this you have no choice but to keep
a fully populated at all times S2 around, why not use that for the CPU
too to avoid faults?

I guess there is a reason, but maybe explain in the commit message?

It sure would be simpler, you wouldn't have to mess with iopgtable at
all...

Jason