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 7196FC3ABBE for ; Thu, 8 May 2025 12:30:22 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uD0NT-00007m-6B; Thu, 08 May 2025 08:29:27 -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 1uD0NO-00005b-5G for qemu-devel@nongnu.org; Thu, 08 May 2025 08:29:22 -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 1uD0NL-00030L-S6 for qemu-devel@nongnu.org; Thu, 08 May 2025 08:29:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1746707357; 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=pIfmDn0L2hS+a4AbQgxeNyVM1msdtAX5PQyGCvgqQeE=; b=bFWNkHGoeUOj0sxCfLbaglhSItaANahxUz6oNfIVnKXQny/HOzQZUtCWeNooSEW6CAdbpy QVBdEfewuNJCFFEa55SZNAY/N7bjIBYQM0L4X83/76yJNCvyivxNOczGgLcC2ah+BFYpgv 7YDkRq+5lS4aLxPF1Ur8xpJZkaRi6po= 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-183-ajbJshNyOsOtIVH9yqYTKQ-1; Thu, 08 May 2025 08:29:15 -0400 X-MC-Unique: ajbJshNyOsOtIVH9yqYTKQ-1 X-Mimecast-MFC-AGG-ID: ajbJshNyOsOtIVH9yqYTKQ_1746707354 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 90DA11800261; Thu, 8 May 2025 12:29:14 +0000 (UTC) Received: from kaapi.redhat.com (unknown [10.74.64.196]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F0E5418003FD; Thu, 8 May 2025 12:29:10 +0000 (UTC) From: Prasad Pandit To: qemu-devel@nongnu.org Cc: peterx@redhat.com, farosas@suse.de, berrange@redhat.com, Prasad Pandit Subject: [PATCH v10 3/3] migration: write zero pages when postcopy enabled Date: Thu, 8 May 2025 17:58:49 +0530 Message-ID: <20250508122849.207213-4-ppandit@redhat.com> In-Reply-To: <20250508122849.207213-1-ppandit@redhat.com> References: <20250508122849.207213-1-ppandit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=ppandit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.416, 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_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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 are written if they are migrated more than ones. This may result in a migration 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(-) v10: new patch, not present in v9 or earlier versions. diff --git a/migration/multifd-zero-page.c b/migration/multifd-zero-page.c index dbc1184921..9bfb3ef803 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])) { + + /* + * During multifd migration zero page is written to the memory + * only if it is migrated more than ones. + * + * 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 + * migration hangs. + * + * When Postcopy is enabled, always write the zero page as and when + * it is migrated. + * + */ + if (migrate_postcopy_ram() || + ramblock_recv_bitmap_test_byte_offset(p->block, p->zero[i])) { memset(page, 0, multifd_ram_page_size()); - } else { + } + if (!ramblock_recv_bitmap_test_byte_offset(p->block, p->zero[i])) { ramblock_recv_bitmap_set_offset(p->block, p->zero[i]); } } -- 2.49.0