From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2C331E810D5 for ; Wed, 27 Sep 2023 11:47:13 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qlT0P-0001nV-9f; Wed, 27 Sep 2023 07:47:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qlT0G-0001iE-UK for qemu-devel@nongnu.org; Wed, 27 Sep 2023 07:46:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qlT0C-0001St-V9 for qemu-devel@nongnu.org; Wed, 27 Sep 2023 07:46:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695815204; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=0GhUIXt6qAnvJmw9oyTeq3BVbXnYznVDmDu5poktc3Q=; b=hSquYBu2uTkqbpRSie1E/ufY1DhD6s9grWEaKdXCgJux/NVODR+QwHx1PqlcXWBXxdkUcq DcsAItMMbHF1cuYYqml7eKvv49B7OVDrw0E+t98PR5Pu7VXkU9H7P+x5eYiqUQVcYDQC+N msGy5OO4HKKWXVKsyoBS1b403eOB2GY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-601-sMjhnHSuOuSjpaV1w0MbAA-1; Wed, 27 Sep 2023 07:46:42 -0400 X-MC-Unique: sMjhnHSuOuSjpaV1w0MbAA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2155B80349C; Wed, 27 Sep 2023 11:46:42 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F0D9F176C3; Wed, 27 Sep 2023 11:46:41 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id DE09921E6900; Wed, 27 Sep 2023 13:46:40 +0200 (CEST) From: Markus Armbruster To: "Zhijian Li (Fujitsu)" Cc: "qemu-devel@nongnu.org" , "quintela@redhat.com" , "peterx@redhat.com" , "leobras@redhat.com" Subject: Re: [PATCH 39/52] migration/rdma: Convert qemu_rdma_write_one() to Error References: <20230918144206.560120-1-armbru@redhat.com> <20230918144206.560120-40-armbru@redhat.com> <9e117d0c-cf2b-dd01-7fef-55d1c41d254c@fujitsu.com> <87ttrhgu9e.fsf@pond.sub.org> Date: Wed, 27 Sep 2023 13:46:40 +0200 In-Reply-To: <87ttrhgu9e.fsf@pond.sub.org> (Markus Armbruster's message of "Tue, 26 Sep 2023 11:26:37 +0200") Message-ID: <87zg17dejj.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=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: 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 migration/rdma.c uses errno directly or via perror() after the following functions: * poll() POSIX specifies errno is set on error. Good. * rdma_get_cm_event(), rdma_connect(), rdma_get_cm_event() Manual page promises "if an error occurs, errno will be set". Good. * ibv_open_device() Manual page does not mention errno. Using it seems ill-advised. qemu_rdma_broken_ipv6_kernel() recovers from EPERM by trying the next device. Wrong if ibv_open_device() doesn't actually set errno. What is to be done here? * ibv_reg_mr() Manual page does not mention errno. Using it seems ill-advised. qemu_rdma_reg_whole_ram_blocks() and qemu_rdma_register_and_get_keys() recover from errno = ENOTSUP by retrying with modified @access argument. Wrong if ibv_reg_mr() doesn't actually set errno. What is to be done here? * ibv_get_cq_event() Manual page does not mention errno. Using it seems ill-advised. qemu_rdma_block_for_wrid() calls perror(). Removed in PATCH 48. Good enough. * ibv_post_send() Manual page has the function return "the value of errno on failure". Sounds like it sets errno to the value it returns. However, the rdma-core repository defines it as static inline int ibv_post_send(struct ibv_qp *qp, struct ibv_send_wr *wr, struct ibv_send_wr **bad_wr) { return qp->context->ops.post_send(qp, wr, bad_wr); } and at least one of the methods fails without setting errno: static int mana_post_send(struct ibv_qp *ibqp, struct ibv_send_wr *wr, struct ibv_send_wr **bad) { /* This version of driver supports RAW QP only. * Posting WR is done directly in the application. */ return EOPNOTSUPP; } qemu_rdma_write_one() calls perror(). PATCH 39 (this one) replaces it by error_setg(), not error_setg_errno(). Seems prudent, but should be called out in the commit message. * ibv_advise_mr() Manual page has the function return "the value of errno on failure". Sounds like it sets errno to the value it returns, but my findings for ibv_post_send() make me doubt it. qemu_rdma_advise_prefetch_mr() traces strerror(errno). Could be misleading. Drop that part? * ibv_dereg_mr() Manual page has the function return "the value of errno on failure". Sounds like it sets errno to the value it returns, but my findings for ibv_post_send() make me doubt it. qemu_rdma_unregister_waiting() calls perror(). Removed in PATCH 51. Good enough. * qemu_get_cm_event_timeout() Can fail without setting errno. qemu_rdma_connect() calls perror(). Removed in PATCH 45. Good enough. Thoughts? [...] [*] https://github.com/linux-rdma/rdma-core.git commit 55fa316b4b18f258d8ac1ceb4aa5a7a35b094dcf