Re: [PATCH v6 18/18] RDMA/mlx5: Ask P2PDMA whether ATS takes a direct peer-to-peer route

[Jason Gunthorpe]

On Thu, Sep 17, 2026 at 03:56:12PM +0200, Thomas Hellström wrote:

> That is, a flag to tell the topology check that some transactions
> *will* take the host-bridge path due to IOVA being used, and that the
> computations including pci_p2pdma_distance() need to check whether that
> is possible (checking whitelist etc.) and return the corresponding
> THRU_HOST_BRIDGE mapping type. Translated transactions taking a short-
> cut using the bus-address would then be hidden from the driver.

I imagined it would work by the driver passing in what modes it
supports and Intel GPU would simply pass in ATS only.

Even something like mlx has variation, only some operations can opt
into ATS, many others are never-ATS.

Driver should not make statements like " *will* take the host-bridge
path" since it has no idea.

Jason