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dma-buf: heaps: system: document system_cc_shared heap

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Document the system_cc_shared dma-buf heap that was introduced
recently. Describe its purpose, availability conditions and
relation to confidential computing VMs.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: T.J.Mercier <tjmercier@google.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260407092617.635223-1-jiri@resnulli.us
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Jiri Pirko
2026-04-07 11:26:17 +02:00
committed by Marek Szyprowski
parent 78b30c50a7
commit 15818b2cd4
1 changed files with 7 additions and 0 deletions
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7
Documentation/userspace-api/dma-buf-heaps.rst
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@@ -16,6 +16,13 @@ following heaps:
- The ``system`` heap allocates virtually contiguous, cacheable, buffers. - The ``system`` heap allocates virtually contiguous, cacheable, buffers.
- The ``system_cc_shared`` heap allocates virtually contiguous, cacheable,
buffers using shared (decrypted) memory. It is only present on
confidential computing (CoCo) VMs where memory encryption is active
(e.g., AMD SEV, Intel TDX). The allocated pages have the encryption
bit cleared, making them accessible for device DMA without TDISP
support. On non-CoCo VM configurations, this heap is not registered.
- The ``default_cma_region`` heap allocates physically contiguous, - The ``default_cma_region`` heap allocates physically contiguous,
cacheable, buffers. Only present if a CMA region is present. Such a cacheable, buffers. Only present if a CMA region is present. Such a
region is usually created either through the kernel commandline region is usually created either through the kernel commandline