IBV_MODIFY_QP(3)

NAME
ibv_modify_qp - modify the attributes of a queue pair (QP)

SYNOPSIS
#include <infiniband/verbs.h>

int ibv_modify_qp(struct ibv_qp *qp, struct ibv_qp_attr *attr,
                  int attr_mask);

DESCRIPTION
ibv_modify_qp() modifies the attributes of QP qp with the attributes in attr according to the mask attr_mask. The argument attr is an ibv_qp_attr struct, as defined in <infiniband/verbs.h>.

struct ibv_qp_attr {
enum ibv_qp_state       qp_state;               /* Move the QP to this state */
enum ibv_qp_state       cur_qp_state;           /* Assume this is the current QP state */
enum ibv_mtu            path_mtu;               /* Path MTU (valid only for RC/UC QPs) */
enum ibv_mig_state      path_mig_state;         /* Path migration state (valid if HCA supports APM) */
uint32_t                qkey;                   /* Q_Key for the QP (valid only for UD QPs) */
uint32_t                rq_psn;                 /* PSN for receive queue (valid only for RC/UC QPs) */
uint32_t                sq_psn;                 /* PSN for send queue (valid only for RC/UC QPs) */
uint32_t                dest_qp_num;            /* Destination QP number (valid only for RC/UC QPs) */
int                     qp_access_flags;        /* Mask of enabled remote access operations (valid only for RC/UC QPs) */
struct ibv_qp_cap       cap;                    /* QP capabilities (valid if HCA supports QP resizing) */
struct ibv_ah_attr      ah_attr;                /* Primary path address vector (valid only for RC/UC QPs) */
struct ibv_ah_attr      alt_ah_attr;            /* Alternate path address vector (valid only for RC/UC QPs) */
uint16_t                pkey_index;             /* Primary P_Key index */
uint16_t                alt_pkey_index;         /* Alternate P_Key index */
uint8_t                 en_sqd_async_notify;    /* Enable SQD.drained async notification (Valid only if qp_state is SQD) */
uint8_t                 sq_draining;            /* Is the QP draining? Irrelevant for ibv_modify_qp() */
uint8_t                 max_rd_atomic;          /* Number of outstanding RDMA reads & atomic operations on the destination QP (valid only for RC QPs) */
uint8_t                 max_dest_rd_atomic;     /* Number of responder resources for handling incoming RDMA reads & atomic operations (valid only for RC QPs) */
uint8_t                 min_rnr_timer;          /* Minimum RNR NAK timer (valid only for RC QPs) */
uint8_t                 port_num;               /* Primary port number */
uint8_t                 timeout;                /* Local ack timeout for primary path (valid only for RC QPs) */
uint8_t                 retry_cnt;              /* Retry count (valid only for RC QPs) */
uint8_t                 rnr_retry;              /* RNR retry (valid only for RC QPs) */
uint8_t                 alt_port_num;           /* Alternate port number */
uint8_t                 alt_timeout;            /* Local ack timeout for alternate path (valid only for RC QPs) */
uint32_t                rate_limit;             /* Rate limit in kbps for packet pacing */
};

For details on struct ibv_qp_cap see the description of ibv_create_qp(). For details on struct ibv_ah_attr see the description of ibv_create_ah().

The argument attr_mask specifies the QP attributes to be modified. The argument is either 0 or the bitwise OR of one or more of the following flags:

IBV_QP_STATE  Modify qp_state

IBV_QP_CUR_STATE  Set cur_qp_state

IBV_QP_EN_SQD_ASYNC_NOTIFY  Set en_sqd_async_notify

IBV_QP_ACCESS_FLAGS  Set qp_access_flags

IBV_QP_PKEY_INDEX  Set pkey_index

IBV_QP_PORT  Set port_num

IBV_QP_QKEY  Set qkey

IBV_QP_AV  Set ah_attr

IBV_QP_PATH_MTU  Set path_mtu

IBV_QP_TIMEOUT  Set timeout

IBV_QP_RETRY_CNT  Set retry_cnt

IBV_QP_RNR_RETRY  Set rnr_retry

IBV_QP_RQ_PSN  Set rq_psn

IBV_QP_MAX_QP_RD_ATOMIC  Set max_rd_atomic

IBV_QP_ALT_PATH  Set the alternative path via: alt_ah_attr, alt_pkey_index, alt_port_num, alt_timeout

IBV_QP_MIN_RNR_TIMER  Set min_rnr_timer

IBV_QP_SQ_PSN  Set sq_psn

IBV_QP_MAX_DEST_RD_ATOMIC  Set max_dest_rd_atomic

IBV_QP_PATH_MIG_STATE  Set path_mig_state

IBV_QP_CAP  Set cap

IBV_QP_DEST_QPN  Set dest_qp_num
    IBV_QP_RATE_LIMIT Set rate_limit

RETURN VALUE
ibv_modify_qp() returns 0 on success, or the value of errno on failure (which indicates the failure reason).

NOTES
If any of the modify attributes or the modify mask are invalid, none of the attributes will be modified (including the QP state).

Not all devices support resizing QPs. To check if a device supports it, check if the IBV_DEVICE_RESIZE_MAX_WR bit is set in the device capabilities flags.

Not all devices support alternate paths. To check if a device supports it, check if the IBV_DEVICE_AUTO_PATH_MIG bit is set in the device capabilities flags.

The following tables indicate for each QP Transport Service Type, the minimum list of attributes that must be changed upon transitioning QP state from: Reset --> Init --> RTR --> RTS.

For QP Transport Service Type  IBV_QPT_UD:

Next state     Required attributes
----------     ----------------------------------------
Init           IBV_QP_STATE, IBV_QP_PKEY_INDEX, IBV_QP_PORT,
               IBV_QP_QKEY
RTR            IBV_QP_STATE
RTS            IBV_QP_STATE, IBV_QP_SQ_PSN

For QP Transport Service Type  IBV_QPT_UC:

Next state     Required attributes
----------     ----------------------------------------
Init           IBV_QP_STATE, IBV_QP_PKEY_INDEX, IBV_QP_PORT,
               IBV_QP_ACCESS_FLAGS
RTR            IBV_QP_STATE, IBV_QP_AV, IBV_QP_PATH_MTU,
               IBV_QP_DEST_QPN, IBV_QP_RQ_PSN
RTS            IBV_QP_STATE, IBV_QP_SQ_PSN

For QP Transport Service Type  IBV_QPT_RC:

Next state     Required attributes
----------     ----------------------------------------
Init           IBV_QP_STATE, IBV_QP_PKEY_INDEX, IBV_QP_PORT,
               IBV_QP_ACCESS_FLAGS
RTR            IBV_QP_STATE, IBV_QP_AV, IBV_QP_PATH_MTU,
               IBV_QP_DEST_QPN, IBV_QP_RQ_PSN,
               IBV_QP_MAX_DEST_RD_ATOMIC, IBV_QP_MIN_RNR_TIMER
RTS            IBV_QP_STATE, IBV_QP_SQ_PSN, IBV_QP_MAX_QP_RD_ATOMIC,
               IBV_QP_RETRY_CNT, IBV_QP_RNR_RETRY, IBV_QP_TIMEOUT

For QP Transport Service Type  IBV_QPT_RAW_PACKET:

Next state     Required attributes
----------     ----------------------------------------
Init           IBV_QP_STATE, IBV_QP_PORT
RTR            IBV_QP_STATE
RTS            IBV_QP_STATE

If port flag IBV_QPF_GRH_REQUIRED is set then ah_attr and alt_ah_attr must be passed with definition of 'struct ibv_ah_attr { .is_global = 1; .grh = {...}; }'.

SEE ALSO
ibv_create_qp(3), ibv_destroy_qp(3), ibv_query_qp(3), ibv_create_ah(3)

AUTHORS

Dotan Barak <dotanba@gmail.com>