- 07 5月, 2007 1 次提交
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由 Roland Dreier 提交于
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: NRoland Dreier <rolandd@cisco.com>
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- 05 2月, 2007 1 次提交
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由 Michael S. Tsirkin 提交于
struct ib_wc currently only includes the local QP number: this matches the IB spec, but seems mostly useless. The following patch replaces this with the pointer to qp itself, and updates all low level drivers and all users. This has the following advantages: - Ability to get a per-qp context through wc->qp->qp_context - Existing drivers already have the qp pointer ready in poll cq, so this change actually saves a tiny bit (extra memory read) on data path (for ehca it would actually be expensive to find the QP pointer when polling a CQ, but ehca does not support SRQ so we can leave wc->qp as NULL for ehca) - Users that need the QP number can still get it through wc->qp->qp_num Use case: In IPoIB connected mode code, I have a common CQ shared by multiple QPs. To track connection usage, I need a way to get at some per-QP context upon the completion, and I would like to avoid allocating context object per work request just to stick a QP pointer into it. With this code, I can just use wc->qp->qp_context. Signed-off-by: NMichael S. Tsirkin <mst@mellanox.co.il> Signed-off-by: NRoland Dreier <rolandd@cisco.com>
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- 31 10月, 2006 1 次提交
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由 Steve Wise 提交于
The Ammasso driver needs to use dma_alloc_coherent() for allocating memory that will be used by the HW for dma. Signed-off-by: NSteve Wise <swise@opengridcomputing.com> Signed-off-by: NRoland Dreier <rolandd@cisco.com>
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- 23 9月, 2006 1 次提交
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由 Tom Tucker 提交于
Add a driver for the Ammasso 1100 gigabit ethernet RNIC. Signed-off-by: NTom Tucker <tom@opengridcomputing.com> Signed-off-by: NSteve Wise <swise@opengridcomputing.com> Signed-off-by: NRoland Dreier <rolandd@cisco.com>
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