Re: [PATCH v5 0/2] dma-buf: heaps: system: add an option to allocate explicitly shared/decrypted memory

Jason Gunthorpe
2026-04-02T12:02:58Z

On Thu, Apr 02, 2026 at 10:52:34AM +0100, Brian Starkey wrote:
> I'm not clear why the heap depends on !CONFIG_HIGHMEM, but I also
> don't know anything about SEV/TDX.

It is because the CC apis, set_memory_decrypted()/etc are slightly
mis-designed. They take in a vaddr to represent the address instead of
a phys_addr_t or a page *

This means the user has to use page_address() and then the whole thing
is incompatible with highmem.

Which is fine, highmem and CC are never turned on together.

Jason