From patchwork Thu Jun 23 16:53:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Dr. David Alan Gilbert" X-Patchwork-Id: 12892970 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 39A3FC43334 for ; Thu, 23 Jun 2022 16:59:50 +0000 (UTC) Received: from localhost ([::1]:60206 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o4QBJ-0007ok-BM for qemu-devel@archiver.kernel.org; Thu, 23 Jun 2022 12:59:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60258) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o4Q5t-0005uR-39 for qemu-devel@nongnu.org; Thu, 23 Jun 2022 12:54:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:28043) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o4Q5r-0005wf-5i for qemu-devel@nongnu.org; Thu, 23 Jun 2022 12:54:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656003250; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+jPmpDSwRTFoYmOjQmvGMUYdM/c1OD/+RnzJ9cp02DA=; b=QVHdC9ZmSCzJU86eNMQCkxHvgamafL1wLGVFPKTfbv347eom3ZAkNR2cKiL/+zYaapsnI+ SkrOz8fA8buHccvHGcyYddk0eOVxWwzGY+gvG8C4grOT8cqCh4Dzw5P0stSADzctk2eDBS s4ZJSx9c3whEvGfQDaDtwwmYujWFJf8= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-99-l2XG4xNgP7SegALCbw_2LA-1; Thu, 23 Jun 2022 12:54:09 -0400 X-MC-Unique: l2XG4xNgP7SegALCbw_2LA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BFC283C0D191; Thu, 23 Jun 2022 16:54:08 +0000 (UTC) Received: from dgilbert-t580.localhost (unknown [10.33.36.159]) by smtp.corp.redhat.com (Postfix) with ESMTP id C351C2026D64; Thu, 23 Jun 2022 16:54:07 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, berrange@redhat.com, huangy81@chinatelecom.cn, quintela@redhat.com, leobras@redhat.com, peterx@redhat.com Cc: jdenemar@redhat.com Subject: [PULL 07/25] migration: remove unreachble RDMA code in save_hook impl Date: Thu, 23 Jun 2022 17:53:36 +0100 Message-Id: <20220623165354.197792-8-dgilbert@redhat.com> In-Reply-To: <20220623165354.197792-1-dgilbert@redhat.com> References: <20220623165354.197792-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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" From: Daniel P. Berrangé The QEMUFile 'save_hook' callback has a 'size_t size' parameter. The RDMA impl of this has logic that takes different actions depending on whether the value is zero or non-zero. It has commented out logic that would have taken further actions if the value was negative. The only place where the 'save_hook' callback is invoked is the ram_control_save_page() method, which passes 'size' through from its caller. The only caller of this method is in turn control_save_page(). This method unconditionally passes the 'TARGET_PAGE_SIZE' constant for the 'size' parameter. IOW, the only scenario for 'size' that can execute in the qemu_rdma_save_page method is 'size > 0'. The remaining code has been unreachable since RDMA support was first introduced 9 years ago. Reviewed-by: Eric Blake Reviewed-by: Dr. David Alan Gilbert Signed-off-by: Daniel P. Berrangé Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela Signed-off-by: Dr. David Alan Gilbert --- migration/rdma.c | 120 +++++++++-------------------------------------- 1 file changed, 21 insertions(+), 99 deletions(-) diff --git a/migration/rdma.c b/migration/rdma.c index 8504152f39..c5fa4a408a 100644 --- a/migration/rdma.c +++ b/migration/rdma.c @@ -1462,34 +1462,6 @@ static uint64_t qemu_rdma_make_wrid(uint64_t wr_id, uint64_t index, return result; } -/* - * Set bit for unregistration in the next iteration. - * We cannot transmit right here, but will unpin later. - */ -static void qemu_rdma_signal_unregister(RDMAContext *rdma, uint64_t index, - uint64_t chunk, uint64_t wr_id) -{ - if (rdma->unregistrations[rdma->unregister_next] != 0) { - error_report("rdma migration: queue is full"); - } else { - RDMALocalBlock *block = &(rdma->local_ram_blocks.block[index]); - - if (!test_and_set_bit(chunk, block->unregister_bitmap)) { - trace_qemu_rdma_signal_unregister_append(chunk, - rdma->unregister_next); - - rdma->unregistrations[rdma->unregister_next++] = - qemu_rdma_make_wrid(wr_id, index, chunk); - - if (rdma->unregister_next == RDMA_SIGNALED_SEND_MAX) { - rdma->unregister_next = 0; - } - } else { - trace_qemu_rdma_signal_unregister_already(chunk); - } - } -} - /* * Consult the connection manager to see a work request * (of any kind) has completed. @@ -3237,23 +3209,7 @@ qio_channel_rdma_shutdown(QIOChannel *ioc, * Offset is an offset to be added to block_offset and used * to also lookup the corresponding RAMBlock. * - * @size > 0 : - * Initiate an transfer this size. - * - * @size == 0 : - * A 'hint' or 'advice' that means that we wish to speculatively - * and asynchronously unregister this memory. In this case, there is no - * guarantee that the unregister will actually happen, for example, - * if the memory is being actively transmitted. Additionally, the memory - * may be re-registered at any future time if a write within the same - * chunk was requested again, even if you attempted to unregister it - * here. - * - * @size < 0 : TODO, not yet supported - * Unregister the memory NOW. This means that the caller does not - * expect there to be any future RDMA transfers and we just want to clean - * things up. This is used in case the upper layer owns the memory and - * cannot wait for qemu_fclose() to occur. + * @size : Number of bytes to transfer * * @bytes_sent : User-specificed pointer to indicate how many bytes were * sent. Usually, this will not be more than a few bytes of @@ -3282,61 +3238,27 @@ static size_t qemu_rdma_save_page(QEMUFile *f, void *opaque, qemu_fflush(f); - if (size > 0) { - /* - * Add this page to the current 'chunk'. If the chunk - * is full, or the page doesn't belong to the current chunk, - * an actual RDMA write will occur and a new chunk will be formed. - */ - ret = qemu_rdma_write(f, rdma, block_offset, offset, size); - if (ret < 0) { - error_report("rdma migration: write error! %d", ret); - goto err; - } - - /* - * We always return 1 bytes because the RDMA - * protocol is completely asynchronous. We do not yet know - * whether an identified chunk is zero or not because we're - * waiting for other pages to potentially be merged with - * the current chunk. So, we have to call qemu_update_position() - * later on when the actual write occurs. - */ - if (bytes_sent) { - *bytes_sent = 1; - } - } else { - uint64_t index, chunk; - - /* TODO: Change QEMUFileOps prototype to be signed: size_t => long - if (size < 0) { - ret = qemu_rdma_drain_cq(f, rdma); - if (ret < 0) { - fprintf(stderr, "rdma: failed to synchronously drain" - " completion queue before unregistration.\n"); - goto err; - } - } - */ - - ret = qemu_rdma_search_ram_block(rdma, block_offset, - offset, size, &index, &chunk); - - if (ret) { - error_report("ram block search failed"); - goto err; - } - - qemu_rdma_signal_unregister(rdma, index, chunk, 0); + /* + * Add this page to the current 'chunk'. If the chunk + * is full, or the page doesn't belong to the current chunk, + * an actual RDMA write will occur and a new chunk will be formed. + */ + ret = qemu_rdma_write(f, rdma, block_offset, offset, size); + if (ret < 0) { + error_report("rdma migration: write error! %d", ret); + goto err; + } - /* - * TODO: Synchronous, guaranteed unregistration (should not occur during - * fast-path). Otherwise, unregisters will process on the next call to - * qemu_rdma_drain_cq() - if (size < 0) { - qemu_rdma_unregister_waiting(rdma); - } - */ + /* + * We always return 1 bytes because the RDMA + * protocol is completely asynchronous. We do not yet know + * whether an identified chunk is zero or not because we're + * waiting for other pages to potentially be merged with + * the current chunk. So, we have to call qemu_update_position() + * later on when the actual write occurs. + */ + if (bytes_sent) { + *bytes_sent = 1; } /*