Re: [PATCH 2/3] dma-mapping: Clarify valid conditions for CPU cache line overlap

[Jason Gunthorpe]

On Mon, Mar 09, 2026 at 01:30:24PM +0100, Marek Szyprowski wrote:

> My question here is if RDMA works on any non-coherent DMA systems? 

The in kernel components do work, like storage, nvme over fabrics, netdev.

The user API (uverbs) does not work at all, and has never worked.

I think DRM has similar issues too where most of their DMA API usage
is OK but some places where they interact win pin_user_pages() have
the same issues as RDMA.

This is why I'd like a new attribute DMA_ATTR_REQUIRE_COHERENCE that
these special cases can use to fail instead of data corrupt.

Jason