On Tue, Jan 27, 2026 at 09:50:55AM -0800, Nicolin Chen wrote:

On Tue, Jan 27, 2026 at 11:41:11AM -0400, Jason Gunthorpe wrote:

quoted

On Wed, Jan 21, 2026 at 05:24:28PM -0800, Nicolin Chen wrote:

quoted

VMM needs a domain holding the mappings between gPA to hPA. It can be an S1
domain or an S2 nesting parent domain, depending on whether the VM is built
with a vSMMU or not.

Given that the IOAS for this gPA mapping is the same across SMMU instances,
this domain can be shared across devices even if they sit behind different
SMMUs, so long as the underlying page table is compatible between the SMMU
instances.

There is no direct information about the page table from the master device,
but a comparison can be done between the physical SMMU that the domain was
allocated for and the physical SMMU that the device is behind.

I would very much prefer this works by inspecting the cfg from the
iopgtable..

You can get it by doing 

	struct io_pgtable_cfg *pgtbl_cfg =
		&io_pgtable_ops_to_pgtable(domain->pgtbl_ops)->cfg;

OK. I will make it a detailed scan

quoted

I think it is important that the domain->smmu pointer be removed as
well

I will try that too.

There are smmu_domain->smmu validations in two SVA functions,
which presumably might be replaced with this can_share() too.

Those are because we replicate the mmu notifier for every
instance. That can now be revised too, I think. Let's leave that for
another series after this and leave the smmu pointer for now, but
don't use it outside that SVA stuff.

Jason