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 0C32BC3ABD7 for ; Mon, 12 May 2025 12:52:33 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uESdR-0008WA-A5; Mon, 12 May 2025 08:51:57 -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 1uESdO-0008VD-Tu for qemu-devel@nongnu.org; Mon, 12 May 2025 08:51:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uESdL-0005cE-Ph for qemu-devel@nongnu.org; Mon, 12 May 2025 08:51:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747054305; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NqO6v2f8ptpnS0y81ZBzuNwN7yATriyketYADzQ9aB8=; b=P30EsmX/PeCvUqMuDARfoFVDaa7f1YGktvlnfUztScy7loZU4VNi/J/b2zJc3hGWCx7g04 T1UFGP43TxrlcFs1Mq/7N3r98PVHlz+xi+cB8ukQcPp77y3N8RrdkrCgAg+dIQNRwoQ4h5 iSyDfjDjo0R1FOtSTqGYUhowyIQpq4c= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-630-S0ui_tnmPEehuukHWdJGXg-1; Mon, 12 May 2025 08:51:43 -0400 X-MC-Unique: S0ui_tnmPEehuukHWdJGXg-1 X-Mimecast-MFC-AGG-ID: S0ui_tnmPEehuukHWdJGXg_1747054301 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 00BAE1800446; Mon, 12 May 2025 12:51:41 +0000 (UTC) Received: from kaapi.redhat.com (unknown [10.74.80.184]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6A71219560A3; Mon, 12 May 2025 12:51:36 +0000 (UTC) From: Prasad Pandit To: qemu-devel@nongnu.org Cc: peterx@redhat.com, farosas@suse.de, berrange@redhat.com, Prasad Pandit Subject: [PATCH v11 1/3] migration: write zero pages when postcopy enabled Date: Mon, 12 May 2025 18:21:22 +0530 Message-ID: <20250512125124.147064-2-ppandit@redhat.com> In-Reply-To: <20250512125124.147064-1-ppandit@redhat.com> References: <20250512125124.147064-1-ppandit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass client-ip=170.10.133.124; envelope-from=ppandit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.551, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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 From: Prasad Pandit During multifd migration, zero pages are written if they are migrated more than once. This may result in a migration thread hang issue when multifd and postcopy are enabled together. When postcopy is enabled, always write zero pages as and when they are migrated. Signed-off-by: Prasad Pandit --- migration/multifd-zero-page.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) v11: - s/ones/once, remove capitalisations and call _test_byte_offset() once v10: - https://lore.kernel.org/qemu-devel/20250508122849.207213-2-ppandit@redhat.com/T/#t diff --git a/migration/multifd-zero-page.c b/migration/multifd-zero-page.c index dbc1184921..4cde868159 100644 --- a/migration/multifd-zero-page.c +++ b/migration/multifd-zero-page.c @@ -85,9 +85,27 @@ void multifd_recv_zero_page_process(MultiFDRecvParams *p) { for (int i = 0; i < p->zero_num; i++) { void *page = p->host + p->zero[i]; - if (ramblock_recv_bitmap_test_byte_offset(p->block, p->zero[i])) { + bool received = + ramblock_recv_bitmap_test_byte_offset(p->block, p->zero[i]); + + /* + * During multifd migration zero page is written to the memory + * only if it is migrated more than once. + * + * It becomes a problem when both multifd & postcopy options are + * enabled. If the zero page which was skipped during multifd phase, + * is accessed during the postcopy phase of the migration, a page + * fault occurs. But this page fault is not served because the + * 'receivedmap' says the zero page is already received. Thus the + * thread accessing that page may hang. + * + * When postcopy is enabled, always write the zero page as and when + * it is migrated. + */ + if (migrate_postcopy_ram() || received) { memset(page, 0, multifd_ram_page_size()); - } else { + } + if (!received) { ramblock_recv_bitmap_set_offset(p->block, p->zero[i]); } } -- 2.49.0