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

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Message-ID: <Y3+sb3RZkEO3ISpW@nvidia.com>
Date:   Thu, 24 Nov 2022 13:39:59 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "lizhijian@...itsu.com" <lizhijian@...itsu.com>
Cc:     "zyjzyj2000@...il.com" <zyjzyj2000@...il.com>,
        "leon@...nel.org" <leon@...nel.org>,
        Bob Pearson <rpearsonhpe@...il.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Mark Bloch <mbloch@...dia.com>, Tom Talpey <tom@...pey.com>,
        "tomasz.gromadzki@...el.com" <tomasz.gromadzki@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "yangx.jy@...itsu.com" <yangx.jy@...itsu.com>,
        "Yasunori Gotou (Fujitsu)" <y-goto@...itsu.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [for-next PATCH v6 09/10] RDMA/cm: Make QP FLUSHABLE

On Wed, Nov 23, 2022 at 06:07:37AM +0000, lizhijian@...itsu.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@...il.com>
> >> Signed-off-by: Li Zhijian <lizhijian@...itsu.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?

Jason