On Thu, Jul 02, 2026 at 10:25:16AM +1000, Alexey Kardashevskiy wrote:

quoted

quoted

not externally available so I'll have to trick the DMA layer into
using SWIOTLB (which is still all shared, right?) as I specifically
want to skip page conversions. Setting low DMA mask won't guarantee
that the DMA layer won't allocate a page outside of SWIOTLB and
convert it. Manually do

Why so particular?

aahhh I missed "pre-". I need a way to get pre-shared pages for my
sev-guest activities.

It sounds to me like you don't, what you are worried about is
optimizing the dma_alloc_coherent flow to avoid fragmentation and all
CC architetures require this optimization.

So I'm strongly against you trying to open code something in your
driver. Use the DMA API as-is. Propose general DMA API improvements to
reduce the fragmentation problem. It is a real problem.

Jason