Re: [RFC PATCH 1/4] dma: Add DMA allocation preservation KHO ABI

[Pranjal Shrivastava <praan@google.com>]

On Tue, May 05, 2026 at 12:27:34AM +0000, Samiullah Khawaja wrote:
> The DMA allocations can be backed by a variety of allocators. Add KHO
> ABI for the preservation of contiguous allocations that are done through
> dma-direct.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
>  include/linux/kho/abi/dma_alloc.h | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>  create mode 100644 include/linux/kho/abi/dma_alloc.h
> 
> diff --git a/include/linux/kho/abi/dma_alloc.h b/include/linux/kho/abi/dma_alloc.h
> new file mode 100644
> index 000000000000..46e61db81abe
> --- /dev/null
> +++ b/include/linux/kho/abi/dma_alloc.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LINUX_KHO_ABI_DMA_ALLOC_H
> +#define _LINUX_KHO_ABI_DMA_ALLOC_H
> +
> +#include <linux/types.h>
> +
> +/**
> + * DOC: DMA Alloc ABI
> + *
> + * This header defines the structures used to serialize the state of DMA
> + * allocations, done by device driver, across a Live Update.
> + *
> + * Only DMA allocations done through dma-direct that are contiguous and
> + * allocated using alloc_page are supported.
> + */
> +
> +/**
> + * struct dma_alloc_ser - Serialized state of a single DMA allocation
> + * @page_phys: Physical address of the preserved pages
> + * @size: Size of the DMA allocation
> + * @force_decrypted: Whether the memory is force decrypted in previous kernel
> + */
> +struct dma_alloc_ser {
> +	u64 page_phys;
> +	u64 size;
> +	u8 force_decrypted;

Should we also stope attrs in this ser state here? There might be flags
like DMA_ATTR_NO_KERNEL_MAPPING which would need to be preserved across
a kexec? 

> +	u8 padding[7];
> +} __packed;
> +
> +#endif /* _LINUX_KHO_ABI_DMA_ALLOC_H */
> -- 
> 2.54.0.545.g6539524ca2-goog
> 

Thanks,
Praan