On 2/11/2015 10:40 AM, Weiny, Ira wrote:
>> On 2/4/2015 6:29 PM, ira.weiny@xxxxxxxxx wrote:
>>> From: Ira Weiny <ira.weiny@xxxxxxxxx>
>>>
>>> OPA MADs share a common header with IBTA MADs but with a different
>>> base version and an extended length. These "jumbo" MADs increase the
>>> performance of management traffic.
>>>
>>> Sharing a common header with IBTA MADs allows us to share most of the
>>> MAD processing code when dealing with OPA MADs in addition to
>>> supporting some IBTA MADs on OPA devices.
>>>
>>> Add a device capability flag to indicate OPA MAD support on the device.
>>>
>>> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
>>>
>>> ---
>>> include/rdma/ib_verbs.h | 5 +++++
>>> 1 file changed, 5 insertions(+)
>>>
>>> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h index
>>> 3ab4033..2614233 100644
>>> --- a/include/rdma/ib_verbs.h
>>> +++ b/include/rdma/ib_verbs.h
>>> @@ -128,6 +128,10 @@ enum ib_device_cap_flags {
>>> IB_DEVICE_ON_DEMAND_PAGING = (1<<31),
>>> };
>>>
>>> +enum ib_device_cap_flags2 {
>>> + IB_DEVICE_OPA_MAD_SUPPORT = 1
>>> +};
>>> +
>>> enum ib_signature_prot_cap {
>>> IB_PROT_T10DIF_TYPE_1 = 1,
>>> IB_PROT_T10DIF_TYPE_2 = 1 << 1,
>>> @@ -210,6 +214,7 @@ struct ib_device_attr {
>>> int sig_prot_cap;
>>> int sig_guard_cap;
>>> struct ib_odp_caps odp_caps;
>>> + u64 device_cap_flags2;
>>> u32 max_mad_size;
>>> };
>>>
>>
>> Why is OPA support determined via a device capability flag ? What are the
>> tradeoffs for doing it this way versus the other choices that have been used in
>> the past for other RDMA technologies like RoCE, iWARP, usNIC, ... ?
>
> None of those technologies use the MAD stack for Subnet Management. Other MAD support is very limited (ie IB compatible PMA queries on the local port only).
>
> Do you have a suggestion for alternatives?
The desire to leverage the IB MAD infrastructure for OPA is understood
but the current approach represents OPA as a device capability which
does not seem appropriate because OPA is clearly a different type of
RDMA technology than IB.
-- Hal
> Ira
>
>
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