[Linaro-mm-sig] Re: [PATCH net-next v3 1/2] dma-mapping: introduce DMA_ATTR_CC_DECRYPTED for pre-decrypted memory

On Sun, Mar 08, 2026 at 12:19:48PM +0200, Leon Romanovsky wrote:

...

+/*

• • DMA_ATTR_CC_DECRYPTED: Indicates memory that has been explicitly decrypted
• • (shared) for confidential computing guests. The caller must have
• • called set_memory_decrypted(). A struct page is required.
• */

+#define DMA_ATTR_CC_DECRYPTED (1UL << 12)

While adding the new attribute is fine, I would expect additional checks in dma_map_phys() to ensure the attribute cannot be misused. For example, WARN_ON(attrs & (DMA_ATTR_CC_DECRYPTED | DMA_ATTR_MMIO)), along with a check that we are taking the direct path only.

DECRYPYED and MMIO is something that needs to work, VFIO (inside a TVM) should be using that combination.

Jason