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Date: Mon, 30 Apr 2007 22:11:03 +0200
From: Hoang-Nam Nguyen <HNGUYEN@...ibm.com>
To: Roland Dreier <rdreier@...co.com>
Cc: general@...ts.openfabrics.org,
general-bounces@...ts.openfabrics.org, linux-kernel@...r.kernel.org
Subject: Re: [ofa-general] [PATCH][RFC] IB: Return "maybe missed event" hint from ib_req_notify_cq()
Hi Roland!
As far as this concerns ehca this looks great.
Thanks
Nam
general-bounces@...ts.openfabrics.org wrote on 27.04.2007 00:43:19:
> > - "IB: Return "maybe missed event" hint from ib_req_notify_cq()"
> > This extends the API in a way that lets us implement NAPI, but may
> > be useful for other things too. It touches all the drivers, and I
> > still need to finish updating cxgb3 to work correctly. I haven't
> > heard anything negative about this, so I'll fix it up, post it one
> > more time for review, and plan on merging it.
>
> As promised, here is that patch for review, with a cxgb3
> implementation included.
>
> ---
>
> The semantics defined by the InfiniBand specification say that
> completion events are only generated when a completions is added to a
> completion queue (CQ) after completion notification is requested. In
> other words, this means that the following race is possible:
>
> while (CQ is not empty)
> ib_poll_cq(CQ);
> // new completion is added after while loop is exited
> ib_req_notify_cq(CQ);
> // no event is generated for the existing completion
>
> To close this race, the IB spec recommends doing another poll of the
> CQ after requesting notification.
>
> However, it is not always possible to arrange code this way (for
> example, we have found that NAPI for IPoIB cannot poll after
> requesting notification). Also, some hardware (eg Mellanox HCAs)
> actually will generate an event for completions added before the call
> to ib_req_notify_cq() -- which is allowed by the spec, since there's
> no way for any upper-layer consumer to know exactly when a completion
> was really added -- so the extra poll of the CQ is just a waste.
>
> Motivated by this, we add a new flag "IB_CQ_REPORT_MISSED_EVENTS" for
> ib_req_notify_cq() so that it can return a hint about whether the a
> completion may have been added before the request for notification.
> The return value of ib_req_notify_cq() is extended so:
>
> < 0 means an error occurred while requesting notification
> == 0 means notification was requested successfully, and if
> IB_CQ_REPORT_MISSED_EVENTS was passed in, then no
> events were missed and it is safe to wait for another
> event.
> > 0 is only returned if IB_CQ_REPORT_MISSED_EVENTS was
> passed in. It means that the consumer must poll the
> CQ again to make sure it is empty to avoid the race
> described above.
>
> We add a flag to enable this behavior rather than turning it on
> unconditionally, because checking for missed events may incur
> significant overhead for some low-level drivers, and consumers that
> don't care about the results of this test shouldn't be forced to pay
> for the test.
>
> Signed-off-by: Roland Dreier <rolandd@...co.com>
> ---
> drivers/infiniband/hw/amso1100/c2.h | 2 +-
> drivers/infiniband/hw/amso1100/c2_cq.c | 16 ++++++++---
> drivers/infiniband/hw/cxgb3/cxio_hal.c | 3 ++
> drivers/infiniband/hw/cxgb3/iwch_provider.c | 8 +++--
> drivers/infiniband/hw/ehca/ehca_iverbs.h | 2 +-
> drivers/infiniband/hw/ehca/ehca_reqs.c | 14 +++++++--
> drivers/infiniband/hw/ehca/ipz_pt_fn.h | 8 +++++
> drivers/infiniband/hw/ipath/ipath_cq.c | 15 +++++++---
> drivers/infiniband/hw/ipath/ipath_verbs.h | 2 +-
> drivers/infiniband/hw/mthca/mthca_cq.c | 12 +++++---
> drivers/infiniband/hw/mthca/mthca_dev.h | 4 +-
> include/rdma/ib_verbs.h | 40
> +++++++++++++++++++++------
> 12 files changed, 93 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/infiniband/hw/amso1100/c2.h
> b/drivers/infiniband/hw/amso1100/c2.h
> index 04a9db5..fa58200 100644
> --- a/drivers/infiniband/hw/amso1100/c2.h
> +++ b/drivers/infiniband/hw/amso1100/c2.h
> @@ -519,7 +519,7 @@ extern void c2_free_cq(struct c2_dev *c2dev,
> struct c2_cq *cq);
> extern void c2_cq_event(struct c2_dev *c2dev, u32 mq_index);
> extern void c2_cq_clean(struct c2_dev *c2dev, struct c2_qp *qp,
u32mq_index);
> extern int c2_poll_cq(struct ib_cq *ibcq, int num_entries, struct
> ib_wc *entry);
> -extern int c2_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify notify);
> +extern int c2_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags flags);
>
> /* CM */
> extern int c2_llp_connect(struct iw_cm_id *cm_id,
> diff --git a/drivers/infiniband/hw/amso1100/c2_cq.c
> b/drivers/infiniband/hw/amso1100/c2_cq.c
> index 5175c99..d2b3366 100644
> --- a/drivers/infiniband/hw/amso1100/c2_cq.c
> +++ b/drivers/infiniband/hw/amso1100/c2_cq.c
> @@ -217,17 +217,19 @@ int c2_poll_cq(struct ib_cq *ibcq, int
> num_entries, struct ib_wc *entry)
> return npolled;
> }
>
> -int c2_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify notify)
> +int c2_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags notify_flags)
> {
> struct c2_mq_shared __iomem *shared;
> struct c2_cq *cq;
> + unsigned long flags;
> + int ret = 0;
>
> cq = to_c2cq(ibcq);
> shared = cq->mq.peer;
>
> - if (notify == IB_CQ_NEXT_COMP)
> + if ((notify_flags & IB_CQ_SOLICITED_MASK) == IB_CQ_NEXT_COMP)
> writeb(C2_CQ_NOTIFICATION_TYPE_NEXT, &shared->notification_type);
> - else if (notify == IB_CQ_SOLICITED)
> + else if ((notify_flags & IB_CQ_SOLICITED_MASK) == IB_CQ_SOLICITED)
> writeb(C2_CQ_NOTIFICATION_TYPE_NEXT_SE,
&shared->notification_type);
> else
> return -EINVAL;
> @@ -241,7 +243,13 @@ int c2_arm_cq(struct ib_cq *ibcq, enum
> ib_cq_notify notify)
> */
> readb(&shared->armed);
>
> - return 0;
> + if (notify_flags & IB_CQ_REPORT_MISSED_EVENTS) {
> + spin_lock_irqsave(&cq->lock, flags);
> + ret = !c2_mq_empty(&cq->mq);
> + spin_unlock_irqrestore(&cq->lock, flags);
> + }
> +
> + return ret;
> }
>
> static void c2_free_cq_buf(struct c2_dev *c2dev, struct c2_mq *mq)
> diff --git a/drivers/infiniband/hw/cxgb3/cxio_hal.c
> b/drivers/infiniband/hw/cxgb3/cxio_hal.c
> index f5e9aee..76049af 100644
> --- a/drivers/infiniband/hw/cxgb3/cxio_hal.c
> +++ b/drivers/infiniband/hw/cxgb3/cxio_hal.c
> @@ -114,7 +114,10 @@ int cxio_hal_cq_op(struct cxio_rdev *rdev_p,
> struct t3_cq *cq,
> return -EIO;
> }
> }
> +
> + return 1;
> }
> +
> return 0;
> }
>
> diff --git a/drivers/infiniband/hw/cxgb3/iwch_provider.c
> b/drivers/infiniband/hw/cxgb3/iwch_provider.c
> index 24e0df0..e89957f 100644
> --- a/drivers/infiniband/hw/cxgb3/iwch_provider.c
> +++ b/drivers/infiniband/hw/cxgb3/iwch_provider.c
> @@ -292,7 +292,7 @@ static int iwch_resize_cq(struct ib_cq *cq, int
> cqe, struct ib_udata *udata)
> #endif
> }
>
> -static int iwch_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify notify)
> +static int iwch_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags
flags)
> {
> struct iwch_dev *rhp;
> struct iwch_cq *chp;
> @@ -303,7 +303,7 @@ static int iwch_arm_cq(struct ib_cq *ibcq, enum
> ib_cq_notify notify)
>
> chp = to_iwch_cq(ibcq);
> rhp = chp->rhp;
> - if (notify == IB_CQ_SOLICITED)
> + if ((flags & IB_CQ_SOLICITED_MASK) == IB_CQ_SOLICITED)
> cq_op = CQ_ARM_SE;
> else
> cq_op = CQ_ARM_AN;
> @@ -317,9 +317,11 @@ static int iwch_arm_cq(struct ib_cq *ibcq, enum
> ib_cq_notify notify)
> PDBG("%s rptr 0x%x\n", __FUNCTION__, chp->cq.rptr);
> err = cxio_hal_cq_op(&rhp->rdev, &chp->cq, cq_op, 0);
> spin_unlock_irqrestore(&chp->lock, flag);
> - if (err)
> + if (err < 0)
> printk(KERN_ERR MOD "Error %d rearming CQID 0x%x\n", err,
> chp->cq.cqid);
> + if (err > 0 && !(flags & IB_CQ_REPORT_MISSED_EVENTS))
> + err = 0;
> return err;
> }
>
> diff --git a/drivers/infiniband/hw/ehca/ehca_iverbs.h
> b/drivers/infiniband/hw/ehca/ehca_iverbs.h
> index 95fd59f..9e5460d 100644
> --- a/drivers/infiniband/hw/ehca/ehca_iverbs.h
> +++ b/drivers/infiniband/hw/ehca/ehca_iverbs.h
> @@ -135,7 +135,7 @@ int ehca_poll_cq(struct ib_cq *cq, int
> num_entries, struct ib_wc *wc);
>
> int ehca_peek_cq(struct ib_cq *cq, int wc_cnt);
>
> -int ehca_req_notify_cq(struct ib_cq *cq, enum ib_cq_notify cq_notify);
> +int ehca_req_notify_cq(struct ib_cq *cq, enum ib_cq_notify_flags
> notify_flags);
>
> struct ib_qp *ehca_create_qp(struct ib_pd *pd,
> struct ib_qp_init_attr *init_attr,
> diff --git a/drivers/infiniband/hw/ehca/ehca_reqs.c
> b/drivers/infiniband/hw/ehca/ehca_reqs.c
> index 08d3f89..caec9de 100644
> --- a/drivers/infiniband/hw/ehca/ehca_reqs.c
> +++ b/drivers/infiniband/hw/ehca/ehca_reqs.c
> @@ -634,11 +634,13 @@ poll_cq_exit0:
> return ret;
> }
>
> -int ehca_req_notify_cq(struct ib_cq *cq, enum ib_cq_notify cq_notify)
> +int ehca_req_notify_cq(struct ib_cq *cq, enum ib_cq_notify_flags
> notify_flags)
> {
> struct ehca_cq *my_cq = container_of(cq, struct ehca_cq, ib_cq);
> + unsigned long spl_flags;
> + int ret = 0;
>
> - switch (cq_notify) {
> + switch (notify_flags & IB_CQ_SOLICITED_MASK) {
> case IB_CQ_SOLICITED:
> hipz_set_cqx_n0(my_cq, 1);
> break;
> @@ -649,5 +651,11 @@ int ehca_req_notify_cq(struct ib_cq *cq, enum
> ib_cq_notify cq_notify)
> return -EINVAL;
> }
>
> - return 0;
> + if (notify_flags & IB_CQ_REPORT_MISSED_EVENTS) {
> + spin_lock_irqsave(&my_cq->spinlock, spl_flags);
> + ret = ipz_qeit_is_valid(&my_cq->ipz_queue);
> + spin_unlock_irqrestore(&my_cq->spinlock, spl_flags);
> + }
> +
> + return ret;
> }
> diff --git a/drivers/infiniband/hw/ehca/ipz_pt_fn.h
> b/drivers/infiniband/hw/ehca/ipz_pt_fn.h
> index 8199c45..57f141a 100644
> --- a/drivers/infiniband/hw/ehca/ipz_pt_fn.h
> +++ b/drivers/infiniband/hw/ehca/ipz_pt_fn.h
> @@ -140,6 +140,14 @@ static inline void
> *ipz_qeit_get_inc_valid(struct ipz_queue *queue)
> return cqe;
> }
>
> +static inline int ipz_qeit_is_valid(struct ipz_queue *queue)
> +{
> + struct ehca_cqe *cqe = ipz_qeit_get(queue);
> + u32 cqe_flags = cqe->cqe_flags;
> +
> + return cqe_flags >> 7 == (queue->toggle_state & 1);
> +}
> +
> /*
> * returns and resets Queue Entry iterator
> * returns address (kv) of first Queue Entry
> diff --git a/drivers/infiniband/hw/ipath/ipath_cq.c
> b/drivers/infiniband/hw/ipath/ipath_cq.c
> index 87462e0..9582145 100644
> --- a/drivers/infiniband/hw/ipath/ipath_cq.c
> +++ b/drivers/infiniband/hw/ipath/ipath_cq.c
> @@ -306,17 +306,18 @@ int ipath_destroy_cq(struct ib_cq *ibcq)
> /**
> * ipath_req_notify_cq - change the notification type for a completion
queue
> * @ibcq: the completion queue
> - * @notify: the type of notification to request
> + * @notify_flags: the type of notification to request
> *
> * Returns 0 for success.
> *
> * This may be called from interrupt context. Also called by
> * ib_req_notify_cq() in the generic verbs code.
> */
> -int ipath_req_notify_cq(struct ib_cq *ibcq, enum ib_cq_notify notify)
> +int ipath_req_notify_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags
> notify_flags)
> {
> struct ipath_cq *cq = to_icq(ibcq);
> unsigned long flags;
> + int ret = 0;
>
> spin_lock_irqsave(&cq->lock, flags);
> /*
> @@ -324,9 +325,15 @@ int ipath_req_notify_cq(struct ib_cq *ibcq,
> enum ib_cq_notify notify)
> * any other transitions (see C11-31 and C11-32 in ch. 11.4.2.2).
> */
> if (cq->notify != IB_CQ_NEXT_COMP)
> - cq->notify = notify;
> + cq->notify = notify_flags & IB_CQ_SOLICITED_MASK;
> +
> + if ((notify_flags & IB_CQ_REPORT_MISSED_EVENTS) &&
> + cq->queue->head != cq->queue->tail)
> + ret = 1;
> +
> spin_unlock_irqrestore(&cq->lock, flags);
> - return 0;
> +
> + return ret;
> }
>
> /**
> diff --git a/drivers/infiniband/hw/ipath/ipath_verbs.h
> b/drivers/infiniband/hw/ipath/ipath_verbs.h
> index c0c8d5b..6b3b770 100644
> --- a/drivers/infiniband/hw/ipath/ipath_verbs.h
> +++ b/drivers/infiniband/hw/ipath/ipath_verbs.h
> @@ -716,7 +716,7 @@ struct ib_cq *ipath_create_cq(struct ib_device
> *ibdev, int entries,
>
> int ipath_destroy_cq(struct ib_cq *ibcq);
>
> -int ipath_req_notify_cq(struct ib_cq *ibcq, enum ib_cq_notify notify);
> +int ipath_req_notify_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags
> notify_flags);
>
> int ipath_resize_cq(struct ib_cq *ibcq, int cqe, struct ib_udata
*udata);
>
> diff --git a/drivers/infiniband/hw/mthca/mthca_cq.c
> b/drivers/infiniband/hw/mthca/mthca_cq.c
> index efd79ef..cf0868f 100644
> --- a/drivers/infiniband/hw/mthca/mthca_cq.c
> +++ b/drivers/infiniband/hw/mthca/mthca_cq.c
> @@ -726,11 +726,12 @@ repoll:
> return err == 0 || err == -EAGAIN ? npolled : err;
> }
>
> -int mthca_tavor_arm_cq(struct ib_cq *cq, enum ib_cq_notify notify)
> +int mthca_tavor_arm_cq(struct ib_cq *cq, enum ib_cq_notify_flags flags)
> {
> __be32 doorbell[2];
>
> - doorbell[0] = cpu_to_be32((notify == IB_CQ_SOLICITED ?
> + doorbell[0] = cpu_to_be32(((flags & IB_CQ_SOLICITED_MASK) ==
> + IB_CQ_SOLICITED ?
> MTHCA_TAVOR_CQ_DB_REQ_NOT_SOL :
> MTHCA_TAVOR_CQ_DB_REQ_NOT) |
> to_mcq(cq)->cqn);
> @@ -743,7 +744,7 @@ int mthca_tavor_arm_cq(struct ib_cq *cq, enum
> ib_cq_notify notify)
> return 0;
> }
>
> -int mthca_arbel_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify notify)
> +int mthca_arbel_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags
flags)
> {
> struct mthca_cq *cq = to_mcq(ibcq);
> __be32 doorbell[2];
> @@ -755,7 +756,8 @@ int mthca_arbel_arm_cq(struct ib_cq *ibcq, enum
> ib_cq_notify notify)
>
> doorbell[0] = ci;
> doorbell[1] = cpu_to_be32((cq->cqn << 8) | (2 << 5) | (sn << 3) |
> - (notify == IB_CQ_SOLICITED ? 1 : 2));
> + ((flags & IB_CQ_SOLICITED_MASK) ==
> + IB_CQ_SOLICITED ? 1 : 2));
>
> mthca_write_db_rec(doorbell, cq->arm_db);
>
> @@ -766,7 +768,7 @@ int mthca_arbel_arm_cq(struct ib_cq *ibcq, enum
> ib_cq_notify notify)
> wmb();
>
> doorbell[0] = cpu_to_be32((sn << 28) |
> - (notify == IB_CQ_SOLICITED ?
> + ((flags & IB_CQ_SOLICITED_MASK) == IB_CQ_SOLICITED ?
> MTHCA_ARBEL_CQ_DB_REQ_NOT_SOL :
> MTHCA_ARBEL_CQ_DB_REQ_NOT) |
> cq->cqn);
> diff --git a/drivers/infiniband/hw/mthca/mthca_dev.h
> b/drivers/infiniband/hw/mthca/mthca_dev.h
> index b7e42ef..9bae3cc 100644
> --- a/drivers/infiniband/hw/mthca/mthca_dev.h
> +++ b/drivers/infiniband/hw/mthca/mthca_dev.h
> @@ -495,8 +495,8 @@ void mthca_unmap_eq_icm(struct mthca_dev *dev);
>
> int mthca_poll_cq(struct ib_cq *ibcq, int num_entries,
> struct ib_wc *entry);
> -int mthca_tavor_arm_cq(struct ib_cq *cq, enum ib_cq_notify notify);
> -int mthca_arbel_arm_cq(struct ib_cq *cq, enum ib_cq_notify notify);
> +int mthca_tavor_arm_cq(struct ib_cq *cq, enum ib_cq_notify_flags flags);
> +int mthca_arbel_arm_cq(struct ib_cq *cq, enum ib_cq_notify_flags flags);
> int mthca_init_cq(struct mthca_dev *dev, int nent,
> struct mthca_ucontext *ctx, u32 pdn,
> struct mthca_cq *cq);
> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> index 765589f..529a69d 100644
> --- a/include/rdma/ib_verbs.h
> +++ b/include/rdma/ib_verbs.h
> @@ -431,9 +431,11 @@ struct ib_wc {
> u8 port_num; /* valid only for DR SMPs on switches */
> };
>
> -enum ib_cq_notify {
> - IB_CQ_SOLICITED,
> - IB_CQ_NEXT_COMP
> +enum ib_cq_notify_flags {
> + IB_CQ_SOLICITED = 1 << 0,
> + IB_CQ_NEXT_COMP = 1 << 1,
> + IB_CQ_SOLICITED_MASK = IB_CQ_SOLICITED | IB_CQ_NEXT_COMP,
> + IB_CQ_REPORT_MISSED_EVENTS = 1 << 2,
> };
>
> enum ib_srq_attr_mask {
> @@ -987,7 +989,7 @@ struct ib_device {
> struct ib_wc *wc);
> int (*peek_cq)(struct ib_cq *cq, int wc_cnt);
> int (*req_notify_cq)(struct ib_cq *cq,
> - enum ib_cq_notify cq_notify);
> + enum ib_cq_notify_flags flags);
> int (*req_ncomp_notif)(struct ib_cq *cq,
> int wc_cnt);
> struct ib_mr * (*get_dma_mr)(struct ib_pd *pd,
> @@ -1414,14 +1416,34 @@ int ib_peek_cq(struct ib_cq *cq, int wc_cnt);
> /**
> * ib_req_notify_cq - Request completion notification on a CQ.
> * @cq: The CQ to generate an event for.
> - * @cq_notify: If set to %IB_CQ_SOLICITED, completion notification will
> - * occur on the next solicited event. If set to %IB_CQ_NEXT_COMP,
> - * notification will occur on the next completion.
> + * @flags:
> + * Must contain exactly one of %IB_CQ_SOLICITED or %IB_CQ_NEXT_COMP
> + * to request an event on the next solicited event or next work
> + * completion at any type, respectively. %IB_CQ_REPORT_MISSED_EVENTS
> + * may also be |ed in to request a hint about missed events, as
> + * described below.
> + *
> + * Return Value:
> + * < 0 means an error occurred while requesting notification
> + * == 0 means notification was requested successfully, and if
> + * IB_CQ_REPORT_MISSED_EVENTS was passed in, then no events
> + * were missed and it is safe to wait for another event. In
> + * this case is it guaranteed that any work completions added
> + * to the CQ since the last CQ poll will trigger a completion
> + * notification event.
> + * > 0 is only returned if IB_CQ_REPORT_MISSED_EVENTS was passed
> + * in. It means that the consumer must poll the CQ again to
> + * make sure it is empty to avoid missing an event because of a
> + * race between requesting notification and an entry being
> + * added to the CQ. This return value means it is possible
> + * (but not guaranteed) that a work completion has been added
> + * to the CQ since the last poll without triggering a
> + * completion notification event.
> */
> static inline int ib_req_notify_cq(struct ib_cq *cq,
> - enum ib_cq_notify cq_notify)
> + enum ib_cq_notify_flags flags)
> {
> - return cq->device->req_notify_cq(cq, cq_notify);
> + return cq->device->req_notify_cq(cq, flags);
> }
>
> /**
> --
> 1.5.1.2
> _______________________________________________
> general mailing list
> general@...ts.openfabrics.org
> http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general
>
> To unsubscribe, please visit
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