From patchwork Fri Jun 30 05:22:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?C=C3=A9dric_Le_Goater?= X-Patchwork-Id: 13297599 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 DEFD5EB64D7 for ; Fri, 30 Jun 2023 05:25:07 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qF6bG-0008E0-PR; Fri, 30 Jun 2023 01:23:18 -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 1qF6b1-0008Ah-QU for qemu-devel@nongnu.org; Fri, 30 Jun 2023 01:23:04 -0400 Received: from mail.ozlabs.org ([2404:9400:2221:ea00::3] helo=gandalf.ozlabs.org) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qF6at-0003Ha-FY for qemu-devel@nongnu.org; Fri, 30 Jun 2023 01:22:58 -0400 Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4QskGt6NQRz4wgk; Fri, 30 Jun 2023 15:22:46 +1000 (AEST) Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4QskGr0T6Nz4wZy; Fri, 30 Jun 2023 15:22:43 +1000 (AEST) From: =?utf-8?q?C=C3=A9dric_Le_Goater?= To: qemu-devel@nongnu.org Cc: Richard Henderson , Alex Williamson , Avihai Horon , Peter Xu , Markus Armbruster , YangHang Liu , =?utf-8?q?C=C3=A9dric_Le_Goater?= Subject: [PULL 01/16] migration: Add switchover ack capability Date: Fri, 30 Jun 2023 07:22:20 +0200 Message-ID: <20230630052235.1934154-2-clg@redhat.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230630052235.1934154-1-clg@redhat.com> References: <20230630052235.1934154-1-clg@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2404:9400:2221:ea00::3; envelope-from=SRS0=mf8A=CS=redhat.com=clg@ozlabs.org; helo=gandalf.ozlabs.org X-Spam_score_int: -39 X-Spam_score: -4.0 X-Spam_bar: ---- X-Spam_report: (-4.0 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_PASS=-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-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Avihai Horon Migration downtime estimation is calculated based on bandwidth and remaining migration data. This assumes that loading of migration data in the destination takes a negligible amount of time and that downtime depends only on network speed. While this may be true for RAM, it's not necessarily true for other migrated devices. For example, loading the data of a VFIO device in the destination might require from the device to allocate resources, prepare internal data structures and so on. These operations can take a significant amount of time which can increase migration downtime. This patch adds a new capability "switchover ack" that prevents the source from stopping the VM and completing the migration until an ACK is received from the destination that it's OK to do so. This can be used by migrated devices in various ways to reduce downtime. For example, a device can send initial precopy metadata to pre-allocate resources in the destination and use this capability to make sure that the pre-allocation is completed before the source VM is stopped, so it will have full effect. This new capability relies on the return path capability to communicate from the destination back to the source. The actual implementation of the capability will be added in the following patches. Signed-off-by: Avihai Horon Reviewed-by: Peter Xu Acked-by: Markus Armbruster Tested-by: YangHang Liu Acked-by: Alex Williamson Signed-off-by: Cédric Le Goater --- qapi/migration.json | 12 +++++++++++- migration/options.h | 1 + migration/options.c | 21 +++++++++++++++++++++ 3 files changed, 33 insertions(+), 1 deletion(-) diff --git a/qapi/migration.json b/qapi/migration.json index 5bb5ab82a0cf..47dfef02780f 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -487,6 +487,16 @@ # and should not affect the correctness of postcopy migration. # (since 7.1) # +# @switchover-ack: If enabled, migration will not stop the source VM +# and complete the migration until an ACK is received from the +# destination that it's OK to do so. Exactly when this ACK is +# sent depends on the migrated devices that use this feature. +# For example, a device can use it to make sure some of its data +# is sent and loaded in the destination before doing switchover. +# This can reduce downtime if devices that support this capability +# are present. 'return-path' capability must be enabled to use +# it. (since 8.1) +# # Features: # # @unstable: Members @x-colo and @x-ignore-shared are experimental. @@ -502,7 +512,7 @@ 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate', { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, 'validate-uuid', 'background-snapshot', - 'zero-copy-send', 'postcopy-preempt'] } + 'zero-copy-send', 'postcopy-preempt', 'switchover-ack'] } ## # @MigrationCapabilityStatus: diff --git a/migration/options.h b/migration/options.h index 45991af3c208..9aaf363322b4 100644 --- a/migration/options.h +++ b/migration/options.h @@ -40,6 +40,7 @@ bool migrate_postcopy_ram(void); bool migrate_rdma_pin_all(void); bool migrate_release_ram(void); bool migrate_return_path(void); +bool migrate_switchover_ack(void); bool migrate_validate_uuid(void); bool migrate_xbzrle(void); bool migrate_zero_blocks(void); diff --git a/migration/options.c b/migration/options.c index b62ab30cd585..16007afca662 100644 --- a/migration/options.c +++ b/migration/options.c @@ -185,6 +185,8 @@ Property migration_properties[] = { DEFINE_PROP_MIG_CAP("x-zero-copy-send", MIGRATION_CAPABILITY_ZERO_COPY_SEND), #endif + DEFINE_PROP_MIG_CAP("x-switchover-ack", + MIGRATION_CAPABILITY_SWITCHOVER_ACK), DEFINE_PROP_END_OF_LIST(), }; @@ -308,6 +310,13 @@ bool migrate_return_path(void) return s->capabilities[MIGRATION_CAPABILITY_RETURN_PATH]; } +bool migrate_switchover_ack(void) +{ + MigrationState *s = migrate_get_current(); + + return s->capabilities[MIGRATION_CAPABILITY_SWITCHOVER_ACK]; +} + bool migrate_validate_uuid(void) { MigrationState *s = migrate_get_current(); @@ -547,6 +556,18 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp) } } + if (new_caps[MIGRATION_CAPABILITY_SWITCHOVER_ACK]) { + if (!new_caps[MIGRATION_CAPABILITY_RETURN_PATH]) { + error_setg(errp, "Capability 'switchover-ack' requires capability " + "'return-path'"); + return false; + } + + /* Disable this capability until it's implemented */ + error_setg(errp, "'switchover-ack' is not implemented yet"); + return false; + } + return true; }