From patchwork Tue Mar 18 12:38:46 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Prasad Pandit X-Patchwork-Id: 14020897 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 B74B1C28B2F for ; Tue, 18 Mar 2025 12:40:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tuWEZ-0003Cz-HJ; Tue, 18 Mar 2025 08:39:51 -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 1tuWEN-0002gG-Hu for qemu-devel@nongnu.org; Tue, 18 Mar 2025 08:39:40 -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 1tuWEJ-0007gm-LF for qemu-devel@nongnu.org; Tue, 18 Mar 2025 08:39:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742301574; 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=06iM+9P55Mj7StAkwOGZYdkiRCeTKmpFEP5kkBTrn2A=; b=Z5vwlpNeeVa7xxnFPsmR/gvU3huLAjjK3eTBxpTJtqZvNMS1tc4UnFlpofSZcumgzNyqF0 WYqrSRNMIVGrzY5XO0ZBzsSYjf3//6oKx4+34uPi+XNakShhVxxk6S/DSKM2UjvamP3nSk gmqMOgInk/PiIGn7Iyyy0m/e/1zSwrM= Received: from mx-prod-mc-08.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-39-LcobzCDHNPClf9YLS81t8A-1; Tue, 18 Mar 2025 08:39:31 -0400 X-MC-Unique: LcobzCDHNPClf9YLS81t8A-1 X-Mimecast-MFC-AGG-ID: LcobzCDHNPClf9YLS81t8A_1742301570 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 82F621801A07; Tue, 18 Mar 2025 12:39:30 +0000 (UTC) Received: from kaapi.redhat.com (unknown [10.74.16.234]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 82A481800946; Tue, 18 Mar 2025 12:39:27 +0000 (UTC) From: Prasad Pandit To: qemu-devel@nongnu.org Cc: peterx@redhat.com, farosas@suse.de, berrange@redhat.com Subject: [PATCH v8 7/7] migration/ram: Implement save_postcopy_prepare() Date: Tue, 18 Mar 2025 18:08:46 +0530 Message-ID: <20250318123846.1370312-8-ppandit@redhat.com> In-Reply-To: <20250318123846.1370312-1-ppandit@redhat.com> References: <20250318123846.1370312-1-ppandit@redhat.com> MIME-Version: 1.0 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: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.332, 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: Peter Xu Implement save_postcopy_prepare(), preparing for the enablement of both multifd and postcopy. Please see the rich comment for the rationals. Signed-off-by: Peter Xu Signed-off-by: Prasad Pandit --- migration/ram.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) v8: - New patch v7: - https://lore.kernel.org/qemu-devel/20250228121749.553184-1-ppandit@redhat.com/T/#t diff --git a/migration/ram.c b/migration/ram.c index 6fd88cbf2a..04fde7ba6b 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -4419,6 +4419,42 @@ static int ram_resume_prepare(MigrationState *s, void *opaque) return 0; } +static bool ram_save_postcopy_prepare(QEMUFile *f, void *opaque, Error **errp) +{ + int ret; + + if (migrate_multifd()) { + /* + * When multifd is enabled, source QEMU needs to make sure all the + * pages queued before postcopy starts to be flushed. + * + * Meanwhile, the load of these pages must happen before switching + * to postcopy. It's because loading of guest pages (so far) in + * multifd recv threads is still non-atomic, so the load cannot + * happen with vCPUs running on destination side. + * + * This flush and sync will guarantee those pages loaded _before_ + * postcopy starts on destination. The rational is, this happens + * before VM stops (and before source QEMU sends all the rest of + * the postcopy messages). So when the destination QEMU received + * the postcopy messages, it must have received the sync message on + * the main channel (either RAM_SAVE_FLAG_MULTIFD_FLUSH, or + * RAM_SAVE_FLAG_EOS), and such message should have guaranteed all + * previous guest pages queued in the multifd channels to be + * completely loaded. + */ + ret = multifd_ram_flush_and_sync(f); + if (ret < 0) { + error_setg(errp, "%s: multifd flush and sync failed", __func__); + return false; + } + } + + qemu_put_be64(f, RAM_SAVE_FLAG_EOS); + + return true; +} + void postcopy_preempt_shutdown_file(MigrationState *s) { qemu_put_be64(s->postcopy_qemufile_src, RAM_SAVE_FLAG_EOS); @@ -4438,6 +4474,7 @@ static SaveVMHandlers savevm_ram_handlers = { .load_setup = ram_load_setup, .load_cleanup = ram_load_cleanup, .resume_prepare = ram_resume_prepare, + .save_postcopy_prepare = ram_save_postcopy_prepare, }; static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host,