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Wed, 19 Aug 2026 12:16:59 -0700 (PDT) X-Received: by 2002:a05:620a:2616:b0:912:1206:ddd1 with SMTP id af79cd13be357-9371e31e4fcmr761451785a.1.1787167018456; Wed, 19 Aug 2026 12:16:58 -0700 (PDT) Received: from x1.local ([174.91.117.74]) by smtp.gmail.com with ESMTPSA id af79cd13be357-9372405c33bsm124607085a.29.2026.08.19.12.16.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Aug 2026 12:16:57 -0700 (PDT) Date: Wed, 19 Aug 2026 15:16:49 -0400 From: Peter Xu To: Yanfei Xu Cc: qemu-devel@nongnu.org, farosas@suse.de, lizhijian@fujitsu.com, Jinpu Wang Subject: Re: [PATCH 2/3] migration/rdma: Post initial receive before accepting Message-ID: References: <20260817105117.3072040-1-yanfei.xu@bytedance.com> <20260817105117.3072040-3-yanfei.xu@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260817105117.3072040-3-yanfei.xu@bytedance.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.341, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Aug 17, 2026 at 06:51:16PM +0800, Yanfei Xu wrote: > The source return-path thread can send READY before the destination has > posted its initial receive. Since RNR retries default to zero, the send > can fail and abort migration. > > Post the initial receive before rdma_accept() to close this window. > > Fixes: 55cc1b5937a8 ("migration: create a dedicated connection for rdma return path") > Signed-off-by: Yanfei Xu This one looks correct to me, Reviewed-by: Peter Xu Do you have way to reproduce it, or is this theory (or can be reproduced by adding delays)? > --- > migration/rdma.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/migration/rdma.c b/migration/rdma.c > index e17ace62b0..6e8436ccc1 100644 > --- a/migration/rdma.c > +++ b/migration/rdma.c > @@ -3263,6 +3263,12 @@ static int qemu_rdma_accept(RDMAContext *rdma) > } > } > > + ret = qemu_rdma_post_recv_control(rdma, RDMA_WRID_READY, &err); > + if (ret < 0) { > + error_report_err(err); > + goto err_rdma_dest_wait; > + } > + > /* Accept the second connection request for return path */ > if ((migrate_postcopy() || migrate_return_path()) > && !rdma->is_return_path) { > @@ -3295,12 +3301,6 @@ static int qemu_rdma_accept(RDMAContext *rdma) > rdma_ack_cm_event(cm_event); > rdma->connected = true; > > - ret = qemu_rdma_post_recv_control(rdma, RDMA_WRID_READY, &err); > - if (ret < 0) { > - error_report_err(err); > - goto err_rdma_dest_wait; > - } > - > qemu_rdma_dump_gid("dest_connect", rdma->cm_id); > > return 0; > -- > 2.20.1 > -- Peter Xu