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From: Leon Romanovsky <leon@kernel.org>
To: liweihang <liweihang@huawei.com>
Cc: "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	Linuxarm <linuxarm@huawei.com>
Subject: Re: Question about IB_QP_CUR_STATE
Date: Wed, 8 Jul 2020 15:20:13 +0300	[thread overview]
Message-ID: <20200708122013.GX207186@unreal> (raw)
In-Reply-To: <876ca1eb8667461a9d2e0effb8ee3934@huawei.com>

On Wed, Jul 08, 2020 at 09:41:26AM +0000, liweihang wrote:
> Hi all,
>
> I'm a little confused about the role of IB_QP_CUR_STATE in the enumeration
> ib_qp_attr_mask.
>
> In manual page of ibv_modify_qp(), comments of cur_qp_state is "Assume this
> is the current QP state". Why we need to get current qp state from users
> instead of drivers?
>
> For example, why the users are allowed to modify qp from RTR to RTS again
> even if the qp's state in driver and hardware has already been RTS.
>
> I would be appretiate it if someone can help with this.

See, IBTA section "11.2.5.2 MODIFY QUEUE PAIR", table 96. "Current QP
state" is valid optional attribute in modify_qp() while transition to RTS.

I guess that the reason is to sync QP states seen by SW with HW.

Thanks

>
> Weihang

  reply	other threads:[~2020-07-08 12:20 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-08  9:41 Question about IB_QP_CUR_STATE liweihang
2020-07-08 12:20 ` Leon Romanovsky [this message]
2020-07-08 12:42 ` Gal Pressman
2020-07-08 15:44   ` Leon Romanovsky
2020-07-09  6:13     ` Gal Pressman
2020-07-10 10:11       ` liweihang
2020-07-12 10:44       ` Leon Romanovsky
2020-07-12 10:53         ` Gal Pressman
2020-07-12 11:01           ` Leon Romanovsky

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