RE: [EXTERNAL] Re: [PATCH v3 1/1] lib/dma: introduce inter-process and inter-OS DMA

[Vamsi Krishna Attunuru <vattunuru@marvell.com>]

>
>ZjQcmQRYFpfptBannerEnd
>with below comment fixed:
>Acked-by: Chengwen Feng <fengchengwen@huawei.com>
>
>On 10/13/2025 12:21 PM, Vamsi Krishna wrote:
>> From: Vamsi Attunuru <vattunuru@marvell.com>
>>
>> Modern DMA hardware supports data transfers between multiple DMA
>> devices, facilitating data communication across isolated domains,
>> containers, or operating systems. These DMA transfers function as
>> standard memory-to-memory operations, but with source or destination
>> addresses residing in different process or OS address space. The
>> exchange of these addresses between processes is handled through
>> private driver mechanism, which are beyond the scope of this
>> specification change.
>>
>> This commit introduces new capability flags to advertise driver
>> support for inter-process and inter-OS domain DMA transfers. It adds a
>> mechanism to specify source and destination handlers via the vchan
>configuration.
>> Until standardized control-plane APIs are defined for various
>> categories of DMA devices, these handler details can be exchanged
>> through private driver mechanisms.
>>
>> Signed-off-by: Vamsi Attunuru <vattunuru@marvell.com>
>> ---
>> V3 changes:
>> * Fix v2 review comments
>> V2 changes:
>> * Seperate out the control-plane APIs
>> * Address v0 review comments
>> * Add validation checks
>> * Rename the enums
>>
>>  lib/dmadev/rte_dmadev.c       | 19 +++++++++++
>>  lib/dmadev/rte_dmadev.h       | 59
>+++++++++++++++++++++++++++++++++++
>>  lib/dmadev/rte_dmadev_trace.h |  3 ++
>>  3 files changed, 81 insertions(+)
>>
>> diff --git a/lib/dmadev/rte_dmadev.c b/lib/dmadev/rte_dmadev.c index
>> 17ee0808a9..d6792449bf 100644
>> --- a/lib/dmadev/rte_dmadev.c
>> +++ b/lib/dmadev/rte_dmadev.c
>> @@ -659,6 +659,21 @@ rte_dma_vchan_setup(int16_t dev_id, uint16_t
>vchan,
>>  		RTE_DMA_LOG(ERR, "Device %d vchan out range!", dev_id);
>>  		return -EINVAL;
>>  	}
>> +	if (conf->domain.type != RTE_DMA_INTER_DOMAIN_NONE &&
>> +	    conf->direction != RTE_DMA_DIR_MEM_TO_MEM) {
>> +		RTE_DMA_LOG(ERR, "Device %d inter domain only support
>mem-to-mem transfer", dev_id);
>> +		return -EINVAL;
>> +	}
>> +	if (conf->domain.type == RTE_DMA_INTER_OS_DOMAIN &&
>> +	    !(dev_info.dev_capa & RTE_DMA_CAPA_INTER_OS_DOMAIN)) {
>> +		RTE_DMA_LOG(ERR, "Device %d does not support inter os
>domain", dev_id);
>> +		return -EINVAL;
>> +	}
>> +	if (conf->domain.type == RTE_DMA_INTER_PROCESS_DOMAIN &&
>> +	    !(dev_info.dev_capa &
>RTE_DMA_CAPA_INTER_PROCESS_DOMAIN)) {
>> +		RTE_DMA_LOG(ERR, "Device %d does not support inter
>process domain", dev_id);
>> +		return -EINVAL;
>> +	}
>>  	if (conf->direction != RTE_DMA_DIR_MEM_TO_MEM &&
>>  	    conf->direction != RTE_DMA_DIR_MEM_TO_DEV &&
>>  	    conf->direction != RTE_DMA_DIR_DEV_TO_MEM && @@ -805,6
>+820,8 @@
>> dma_capability_name(uint64_t capability)
>>  		{ RTE_DMA_CAPA_HANDLES_ERRORS, "handles_errors" },
>>  		{ RTE_DMA_CAPA_M2D_AUTO_FREE,  "m2d_auto_free"  },
>>  		{ RTE_DMA_CAPA_PRI_POLICY_SP,  "pri_policy_sp" },
>> +		{ RTE_DMA_CAPA_INTER_PROCESS_DOMAIN,
>"inter_process_domain" },
>> +		{ RTE_DMA_CAPA_INTER_OS_DOMAIN, "inter_os_domain" },
>>  		{ RTE_DMA_CAPA_OPS_COPY,    "copy"    },
>>  		{ RTE_DMA_CAPA_OPS_COPY_SG, "copy_sg" },
>>  		{ RTE_DMA_CAPA_OPS_FILL,    "fill"    },
>> @@ -1014,6 +1031,8 @@ dmadev_handle_dev_info(const char *cmd
>__rte_unused,
>>  	ADD_CAPA(dma_caps, dev_capa,
>RTE_DMA_CAPA_HANDLES_ERRORS);
>>  	ADD_CAPA(dma_caps, dev_capa,
>RTE_DMA_CAPA_M2D_AUTO_FREE);
>>  	ADD_CAPA(dma_caps, dev_capa, RTE_DMA_CAPA_PRI_POLICY_SP);
>> +	ADD_CAPA(dma_caps, dev_capa,
>RTE_DMA_CAPA_INTER_PROCESS_DOMAIN);
>> +	ADD_CAPA(dma_caps, dev_capa,
>RTE_DMA_CAPA_INTER_OS_DOMAIN);
>>  	ADD_CAPA(dma_caps, dev_capa, RTE_DMA_CAPA_OPS_COPY);
>>  	ADD_CAPA(dma_caps, dev_capa, RTE_DMA_CAPA_OPS_COPY_SG);
>>  	ADD_CAPA(dma_caps, dev_capa, RTE_DMA_CAPA_OPS_FILL); diff --
>git
>> a/lib/dmadev/rte_dmadev.h b/lib/dmadev/rte_dmadev.h index
>> 550dbfbf75..4f735bb0c9 100644
>> --- a/lib/dmadev/rte_dmadev.h
>> +++ b/lib/dmadev/rte_dmadev.h
>> @@ -265,6 +265,18 @@ int16_t rte_dma_next_dev(int16_t start_dev_id);
>>   * known from 'nb_priorities' field in struct rte_dma_info.
>>   */
>>  #define RTE_DMA_CAPA_PRI_POLICY_SP	RTE_BIT64(8)
>> +/** Support inter-process DMA transfers.
>> + *
>> + * When this bit is set, the DMA device can perform memory transfers
>> +between
>> + * different process memory spaces.
>> + */
>> +#define RTE_DMA_CAPA_INTER_PROCESS_DOMAIN	RTE_BIT64(9)
>> +/** Support inter-OS domain DMA transfers.
>> + *
>> + * The DMA device can perform memory transfers across different
>> +operating
>> + * system domains.
>> + */
>> +#define RTE_DMA_CAPA_INTER_OS_DOMAIN		RTE_BIT64(10)
>>
>>  /** Support copy operation.
>>   * This capability start with index of 32, so that it could leave gap
>> between @@ -418,8 +430,13 @@ int rte_dma_close(int16_t dev_id);
>>   */
>>  enum rte_dma_direction {
>>  	/** DMA transfer direction - from memory to memory.
>> +	 * When the device supports inter-process or inter-OS domain
>transfers,
>> +	 * the field `type` in `struct rte_dma_vchan_conf::domain` specifies
>the
>> +	 * type of domain. For memory-to-memory transfers within the same
>domain
>> +	 * or process, `type` should be set to
>`RTE_DMA_INTER_DOMAIN_NONE`.
>>  	 *
>>  	 * @see struct rte_dma_vchan_conf::direction
>> +	 * @see struct rte_dma_inter_domain_param::type
>>  	 */
>>  	RTE_DMA_DIR_MEM_TO_MEM,
>>  	/** DMA transfer direction - from memory to device.
>> @@ -564,6 +581,39 @@ struct rte_dma_auto_free_param {
>>  	uint64_t reserved[2];
>>  };
>>
>> +/**
>> + * Inter-DMA transfer domain type.
>> + *
>> + * This enum defines the types of transfer domains applicable to DMA
>operations.
>> + * It helps categorize whether a DMA transfer is occurring within the
>> +same domain,
>> + * across different processes, or between distinct operating system
>domains.
>> + *
>> + * @see struct rte_dma_inter_domain_param:type  */ enum
>> +rte_dma_inter_domain_type {
>> +	/**< No inter-domain transfer; standard DMA within same domaini.
>*/
>> +	RTE_DMA_INTER_DOMAIN_NONE,
>> +	/**< Transfer occurs between different user-space processes. */
>> +	RTE_DMA_INTER_PROCESS_DOMAIN,
>> +	/**< Transfer spans across different operating system domains. */
>> +	RTE_DMA_INTER_OS_DOMAIN,
>
>If comment located before define, it should prefix with ** not **<

Ack, will fix it.
>
>
>> +};
>> +
>> +/**
>> + * Parameters for inter-process or inter-OS DMA transfers.
>> + *
>> + * This structure defines the parameters required to perform DMA
>> +transfers
>> + * across different domains, such as between processes or operating
>systems.
>> + * It includes the domain type and handler identifiers for both the
>> +source
>> + * and destination domains.
>
>I think we could add more comment about how to config use the src/dst
>handler.
>as I comment in before mail:

Sure, will add more comments. I believe a handler value of zero is still valid
for both source and destination. It typically represents the local process when
the transfer direction is mem-to-mem and the inter-domain type if NONE.
Handler values --whether zero or non-zero -- can be used to represent transfers
 From local process to another OS domain, or vice versa. 

Do you have any thoughts on this.?, Specifically, do you foresee any issues with
using handler value of zero.

Thanks
>
>It's mean local process if the src/dst_handler is zero?
>for example, I setup a inter-os domain param, if the src_handle is none zero
>and dst_handle is zero, then all DMA copy will from another OS to local
>process.
>     all DMA fill will write to local process.
>
>If the src_handle is zero and dst_handle is non-zero, then all DMA copy will
>from local process to another OS domain
>     all DMA fill will write to another OS domain.
>
>If both src_handle and dst_handle is non-zero, then all DMA copy will from
>another OS to another OS domain
>     all DMA fill will write to another OS domain.
>
>> + */
>> +struct rte_dma_inter_domain_param {
>> +	enum rte_dma_inter_domain_type type; /**< Type of inter-domain.
>*/
>> +	uint16_t src_handler; /**< Source domain handler identifier. */
>> +	uint16_t dst_handler; /**< Destination domain handler identifier. */
>> +	uint64_t reserved[2]; /**< Reserved for future fields. */
>
>Please move above comment before define to keep the whole header-file
>consistency.
>
>> +};
>> +
>>  /**
>>   * A structure used to configure a virtual DMA channel.
>>   *
>> @@ -601,6 +651,15 @@ struct rte_dma_vchan_conf {
>>  	 * @see struct rte_dma_auto_free_param
>>  	 */
>>  	struct rte_dma_auto_free_param auto_free;
>> +	/** Parameters for inter-process or inter-OS domain DMA transfers.
>This field
>> +	 * specifies the source and destination domain handlers required for
>DMA
>> +	 * operations that span across different processes or operating system
>domains.
>> +	 *
>> +	 * @see RTE_DMA_CAPA_INTER_PROCESS_DOMAIN
>> +	 * @see RTE_DMA_CAPA_INTER_OS_DOMAIN
>> +	 * @see struct rte_dma_inter_domain_param
>> +	 */
>> +	struct rte_dma_inter_domain_param domain;
>>  };
>>
>>  /**
>> diff --git a/lib/dmadev/rte_dmadev_trace.h
>> b/lib/dmadev/rte_dmadev_trace.h index 1de92655f2..fa619c4090 100644
>> --- a/lib/dmadev/rte_dmadev_trace.h
>> +++ b/lib/dmadev/rte_dmadev_trace.h
>> @@ -79,6 +79,9 @@ RTE_TRACE_POINT(
>>  	rte_trace_point_emit_int(conf->dst_port.port_type);
>>  	rte_trace_point_emit_u64(conf->dst_port.pcie.val);
>>  	rte_trace_point_emit_ptr(conf->auto_free.m2d.pool);
>> +	rte_trace_point_emit_int(conf->domain.type);
>> +	rte_trace_point_emit_u16(conf->domain.src_handler);
>> +	rte_trace_point_emit_u16(conf->domain.dst_handler);
>>  	rte_trace_point_emit_int(ret);
>>  )
>>
>
>BTW: please add the UT (test_dmadev_api.c) for above vchan_setup modify,
>this could be another commit I think.
>
Yes, will add it.