Re: [for-next PATCH v6 09/10] RDMA/cm: Make QP FLUSHABLE

lizhijian
2022-11-25T02:22:39Z

On 25/11/2022 01:39, Jason Gunthorpe wrote:
> On Wed, Nov 23, 2022 at 06:07:37AM +0000, lizhijian@fujitsu.com wrote:
>>
>>
>> On 22/11/2022 22:52, Jason Gunthorpe wrote:
>>> On Wed, Nov 16, 2022 at 04:19:50PM +0800, Li Zhijian wrote:
>>>> It enables flushable access flag for qp
>>>>
>>>> Reviewed-by: Zhu Yanjun <zyjzyj2000@gmail.com>
>>>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
>>>> ---
>>>> V5: new patch, inspired by Bob
>>>> ---
>>>> drivers/infiniband/core/cm.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
>>>> index 1f9938a2c475..58837aac980b 100644
>>>> --- a/drivers/infiniband/core/cm.c
>>>> +++ b/drivers/infiniband/core/cm.c
>>>> @@ -4096,7 +4096,8 @@ static int cm_init_qp_init_attr(struct cm_id_private *cm_id_priv,
>>>> qp_attr->qp_access_flags = IB_ACCESS_REMOTE_WRITE;
>>>> if (cm_id_priv->responder_resources)
>>>> qp_attr->qp_access_flags |= IB_ACCESS_REMOTE_READ |
>>>> - IB_ACCESS_REMOTE_ATOMIC;
>>>> + IB_ACCESS_REMOTE_ATOMIC |
>>>> + IB_ACCESS_FLUSHABLE;
>>>
>>> What is the point of this? Nothing checks IB_ACCESS_FLUSHABLE ?
>>
>> Previous, responder of RXE will check qp_access_flags in check_op_valid():
>> 256 static enum resp_states check_op_valid(struct rxe_qp *qp,
>>
>> 257 struct rxe_pkt_info *pkt)
>>
>> 258 {
>>
>> 259 switch (qp_type(qp)) {
>>
>> 260 case IB_QPT_RC:
>>
>> 261 if (((pkt->mask & RXE_READ_MASK) &&
>>
>> 262 !(qp->attr.qp_access_flags &
>> IB_ACCESS_REMOTE_READ)) ||
>>
>>
>> 263 ((pkt->mask & RXE_WRITE_MASK) &&
>>
>> 264 !(qp->attr.qp_access_flags &
>> IB_ACCESS_REMOTE_WRITE)) ||
>> 265 ((pkt->mask & RXE_ATOMIC_MASK) &&
>>
>> 266 !(qp->attr.qp_access_flags &
>> IB_ACCESS_REMOTE_ATOMIC))) {
>> 267 return RESPST_ERR_UNSUPPORTED_OPCODE;
>>
>> 268 }
>>
>> based on this, additional IB_FLUSH_PERSISTENT and IB_ACCESS_FLUSH_GLOBAL
>> were added in patch7 since V5 suggested by Bob.
>> Because of this change, QP should become FLUSHABLE correspondingly.
>
> But nothing ever reads IB_ACCESS_FLUSHABLE, so why is it added?

include/rdma/ib_verbs.h:
+ IB_ACCESS_FLUSH_GLOBAL = IB_UVERBS_ACCESS_FLUSH_GLOBAL,
+ IB_ACCESS_FLUSH_PERSISTENT = IB_UVERBS_ACCESS_FLUSH_PERSISTENT,
+ IB_ACCESS_FLUSHABLE = IB_ACCESS_FLUSH_GLOBAL |
+ IB_ACCESS_FLUSH_PERSISTENT,

IB_ACCESS_FLUSHABLE is a wrapper of IB_ACCESS_FLUSH_GLOBAL |
IB_ACCESS_FLUSH_PERSISTENT. With this wrapper, i will write one less
line of code :)

I'm fine to expand it in next version.

>
> Jason