On Tue, Aug 17, 2021 at 8:54 AM yangx.jy@xxxxxxxxxxx
<yangx.jy@xxxxxxxxxxx> wrote:
>
> On 2021/8/16 15:47, Zhu Yanjun wrote:
> > On Wed, Aug 11, 2021 at 12:33 AM yangx.jy@xxxxxxxxxxx
> > <yangx.jy@xxxxxxxxxxx> wrote:
> >> On 2021/8/10 11:40, Zhu Yanjun wrote:
> >>> On Mon, Aug 9, 2021 at 10:43 PM Xiao Yang<yangx.jy@xxxxxxxxxxx> wrote:
> >>>> Resid indicates the residual length of transmitted bytes but current
> >>>> rxe sets it to zero for inline data at the beginning. In this case,
> >>>> request will transmit zero byte to responder wrongly.
> >>> What are the symptoms if resid is set to zero?
> >> Hi Yanjun,
> >>
> >> You can construct code by the attached patch and then run
> >> rdma_client/server to reproduce the issue.
> >>
> >> If resid is set to zero, running rdma_client/server:
> >> --------------------------------
> >> # ./rdma_client -s 10.167.220.99 -p 8765
> >> rdma_client: start
> >> rdma_client: end 0
> >>
> >> # ./rdma_server -s 10.167.220.99 -p 8765
> >> rdma_server: start
> >> wc.byte_len 0 recv_msg bbbbbbbbbbbbbbbb
> >> rdma_server: end 0
> >> --------------------------------
> >>
> >> rdma_client sends zero byte instead of 16 btyes to rdma_server.
> >> rdma_server receives zero byte instead of 16 btyes from rdma_client.
> >>
> >> Please also see the logic about resid in kernel, for example:
> >> --------------------------------
> >> int rxe_requester(void *arg)
> >> {
> >> ...
> >> payload = (mask& RXE_WRITE_OR_SEND) ? wqe->dma.resid : 0;
> >> ...
> >> skb = init_req_packet(qp, wqe, opcode, payload,&pkt);
> >> ...
> >> }
> >> --------------------------------
> >>
> >> Best Regards,
> >> Xiao Yang
> > Follow your steps on the latest rdma-core and linux upstream,
> > make tests with the followings:
> > "
> > diff --git a/librdmacm/examples/rdma_client.c b/librdmacm/examples/rdma_client.c
> > index c27047c5..6734757b 100644
> > --- a/librdmacm/examples/rdma_client.c
> > +++ b/librdmacm/examples/rdma_client.c
> > @@ -52,6 +52,7 @@ static int run(void)
> > struct ibv_wc wc;
> > int ret;
> >
> > + memset(send_msg, 'a', 16);
> > memset(&hints, 0, sizeof hints);
> > hints.ai_port_space = RDMA_PS_TCP;
> > ret = rdma_getaddrinfo(server, port,&hints,&res);
> > diff --git a/librdmacm/examples/rdma_server.c b/librdmacm/examples/rdma_server.c
> > index f9c766b2..afa20996 100644
> > --- a/librdmacm/examples/rdma_server.c
> > +++ b/librdmacm/examples/rdma_server.c
> > @@ -132,6 +132,7 @@ static int run(void)
> > goto out_disconnect;
> > }
> >
> > + printf("wc.byte_len %u recv_msg %s\n", wc.byte_len, recv_msg);
> > ret = rdma_post_send(id, NULL, send_msg, 16, send_mr, send_flags);
> > if (ret) {
> > perror("rdma_post_send");
> > "
> > The followings are results:
> >
> > # ./build/bin/rdma_server -s 10.238.154.61 -p 5486&
> > [1] 10812
> > # rdma_server: start
> >
> > # ./build/bin/rdma_client -s 10.238.154.61 -p 5486&
> > [2] 10815
> > # rdma_client: start
> > wc.byte_len 16 recv_msg aaaaaaaaaaaaaaaa<--------------it seems
> > that inline is 16?
> > rdma_server: end 0
> > rdma_client: end 0
> > [1]- Done ./build/bin/rdma_server -s 10.238.154.61 -p 5486
> > [2]+ Done ./build/bin/rdma_client -s 10.238.154.61 -p 5486
> >
> > What does your commit fix?
> Hi Yanjun,
>
> You missed the change that sets resid to zero on purpose:
> -------------------------------------------------------------
>
> diff --git a/providers/rxe/rxe.c b/providers/rxe/rxe.c
> index 3c3ea8bb..ed5479fe 100644
> --- a/providers/rxe/rxe.c
> +++ b/providers/rxe/rxe.c
> @@ -1492,7 +1492,7 @@ static int init_send_wqe(struct rxe_qp *qp, struct rxe_wq *sq,
> wqe->iova = ibwr->wr.rdma.remote_addr;
>
> wqe->dma.length = length;
> - wqe->dma.resid = length;
> + wqe->dma.resid = 0;
> wqe->dma.num_sge = num_sge;
> wqe->dma.cur_sge = 0;
> wqe->dma.sge_offset = 0;
>
> -------------------------------------------------------------
> Note:
> It is also ok to remove "wqe->dma.resid = length" here because resid has
> been set to zero before.
>
> With the change, running rdma_client/server will show the impact.
With the original source code, the rdma_server/rdma_client can work well.
Why "wqe->dma.resid = length;" is replaced by "wqe->dma.resid
= 0;", then this problem appears?
Thanks
Zhu Yanjun
>
> I didn't use new API(e.g. ibv_wr_set_inline_data, ibv_wr_send) to create
> a new test
> but it is enough to show the impact of resid == 0 by doing some changes
> on rxe and
> rdma_client/server.
>
> Best Regards,
> Xiao Yang
> > Zhu Yanjun
> >
> >>> Thanks
> >>> Zhu Yanjun
> >>>
> >>>> Resid should be set to the total length of transmitted bytes at the
> >>>> beginning.
> >>>>
> >>>> Note:
> >>>> Just remove the useless setting of resid in init_send_wqe().
> >>>>
> >>>> Fixes: 1a894ca10105 ("Providers/rxe: Implement ibv_create_qp_ex verb")
> >>>> Fixes: 8337db5df125 ("Providers/rxe: Implement memory windows")
> >>>> Signed-off-by: Xiao Yang<yangx.jy@xxxxxxxxxxx>
> >>>> ---
> >>>> providers/rxe/rxe.c | 5 ++---
> >>>> 1 file changed, 2 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/providers/rxe/rxe.c b/providers/rxe/rxe.c
> >>>> index 3c3ea8bb..3533a325 100644
> >>>> --- a/providers/rxe/rxe.c
> >>>> +++ b/providers/rxe/rxe.c
> >>>> @@ -1004,7 +1004,7 @@ static void wr_set_inline_data(struct ibv_qp_ex *ibqp, void *addr,
> >>>>
> >>>> memcpy(wqe->dma.inline_data, addr, length);
> >>>> wqe->dma.length = length;
> >>>> - wqe->dma.resid = 0;
> >>>> + wqe->dma.resid = length;
> >>>> }
> >>>>
> >>>> static void wr_set_inline_data_list(struct ibv_qp_ex *ibqp, size_t num_buf,
> >>>> @@ -1035,6 +1035,7 @@ static void wr_set_inline_data_list(struct ibv_qp_ex *ibqp, size_t num_buf,
> >>>> }
> >>>>
> >>>> wqe->dma.length = tot_length;
> >>>> + wqe->dma.resid = tot_length;
> >>>> }
> >>>>
> >>>> static void wr_set_sge(struct ibv_qp_ex *ibqp, uint32_t lkey, uint64_t addr,
> >>>> @@ -1473,8 +1474,6 @@ static int init_send_wqe(struct rxe_qp *qp, struct rxe_wq *sq,
> >>>> if (ibwr->send_flags& IBV_SEND_INLINE) {
> >>>> uint8_t *inline_data = wqe->dma.inline_data;
> >>>>
> >>>> - wqe->dma.resid = 0;
> >>>> -
> >>>> for (i = 0; i< num_sge; i++) {
> >>>> memcpy(inline_data,
> >>>> (uint8_t *)(long)ibwr->sg_list[i].addr,
> >>>> --
> >>>> 2.25.1
> >>>>
> >>>>
> >>>>
