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163 lines
6.1 KiB
163 lines
6.1 KiB
From 8f89d3bc8f226cd038bf88b9fb3ef43b0fb33034 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@redhat.com>
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Date: Wed, 12 Jul 2023 17:46:57 +0200
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Subject: [PATCH 10/37] migration: Add switchover ack capability
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Cédric Le Goater <clg@redhat.com>
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RH-MergeRequest: 179: vfio: live migration support
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RH-Bugzilla: 2192818
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RH-Acked-by: Eric Auger <eric.auger@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [8/28] 2f4ca020783bd617eca13b18289fce764279833b (clegoate/qemu-kvm-c9s)
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Bugzilla: https://bugzilla.redhat.com/2192818
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commit 6574232fff6a
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Author: Avihai Horon <avihaih@nvidia.com>
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Date: Wed Jun 21 14:11:54 2023 +0300
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migration: Add switchover ack capability
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Migration downtime estimation is calculated based on bandwidth and
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remaining migration data. This assumes that loading of migration data in
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the destination takes a negligible amount of time and that downtime
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depends only on network speed.
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While this may be true for RAM, it's not necessarily true for other
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migrated devices. For example, loading the data of a VFIO device in the
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destination might require from the device to allocate resources, prepare
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internal data structures and so on. These operations can take a
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significant amount of time which can increase migration downtime.
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This patch adds a new capability "switchover ack" that prevents the
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source from stopping the VM and completing the migration until an ACK
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is received from the destination that it's OK to do so.
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This can be used by migrated devices in various ways to reduce downtime.
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For example, a device can send initial precopy metadata to pre-allocate
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resources in the destination and use this capability to make sure that
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the pre-allocation is completed before the source VM is stopped, so it
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will have full effect.
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This new capability relies on the return path capability to communicate
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from the destination back to the source.
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The actual implementation of the capability will be added in the
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following patches.
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Signed-off-by: Avihai Horon <avihaih@nvidia.com>
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Reviewed-by: Peter Xu <peterx@redhat.com>
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Acked-by: Markus Armbruster <armbru@redhat.com>
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Tested-by: YangHang Liu <yanghliu@redhat.com>
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Acked-by: Alex Williamson <alex.williamson@redhat.com>
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Signed-off-by: Cédric Le Goater <clg@redhat.com>
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Conflicts:
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- qapi/migration.json
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re-indent of @switchover-ack to avoid ../qapi/migration.json:482:1:
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unexpected de-indent (expected at least 17 spaces)
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Signed-off-by: Cédric Le Goater <clg@redhat.com>
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---
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migration/options.c | 21 +++++++++++++++++++++
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migration/options.h | 1 +
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qapi/migration.json | 14 +++++++++++++-
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3 files changed, 35 insertions(+), 1 deletion(-)
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diff --git a/migration/options.c b/migration/options.c
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index a76984276d..c3df6c6dde 100644
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--- a/migration/options.c
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+++ b/migration/options.c
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@@ -182,6 +182,8 @@ Property migration_properties[] = {
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DEFINE_PROP_MIG_CAP("x-zero-copy-send",
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MIGRATION_CAPABILITY_ZERO_COPY_SEND),
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#endif
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+ DEFINE_PROP_MIG_CAP("x-switchover-ack",
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+ MIGRATION_CAPABILITY_SWITCHOVER_ACK),
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DEFINE_PROP_END_OF_LIST(),
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};
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@@ -305,6 +307,13 @@ bool migrate_return_path(void)
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return s->capabilities[MIGRATION_CAPABILITY_RETURN_PATH];
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}
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+bool migrate_switchover_ack(void)
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+{
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+ MigrationState *s = migrate_get_current();
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+
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+ return s->capabilities[MIGRATION_CAPABILITY_SWITCHOVER_ACK];
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+}
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+
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bool migrate_validate_uuid(void)
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{
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MigrationState *s = migrate_get_current();
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@@ -532,6 +541,18 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
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}
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}
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+ if (new_caps[MIGRATION_CAPABILITY_SWITCHOVER_ACK]) {
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+ if (!new_caps[MIGRATION_CAPABILITY_RETURN_PATH]) {
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+ error_setg(errp, "Capability 'switchover-ack' requires capability "
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+ "'return-path'");
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+ return false;
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+ }
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+
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+ /* Disable this capability until it's implemented */
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+ error_setg(errp, "'switchover-ack' is not implemented yet");
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+ return false;
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+ }
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+
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return true;
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}
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diff --git a/migration/options.h b/migration/options.h
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index 7b0f7245ad..0fc7be6869 100644
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--- a/migration/options.h
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+++ b/migration/options.h
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@@ -47,6 +47,7 @@ bool migrate_postcopy_ram(void);
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bool migrate_rdma_pin_all(void);
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bool migrate_release_ram(void);
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bool migrate_return_path(void);
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+bool migrate_switchover_ack(void);
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bool migrate_validate_uuid(void);
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bool migrate_xbzrle(void);
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bool migrate_zero_blocks(void);
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diff --git a/qapi/migration.json b/qapi/migration.json
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index 2c35b7b9cf..b6a58347cc 100644
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--- a/qapi/migration.json
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+++ b/qapi/migration.json
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@@ -478,6 +478,18 @@
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# should not affect the correctness of postcopy migration.
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# (since 7.1)
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#
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+# @switchover-ack: If enabled, migration will not stop the source VM
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+# and complete the migration until an ACK is received
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+# from the destination that it's OK to do so.
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+# Exactly when this ACK is sent depends on the
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+# migrated devices that use this feature. For
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+# example, a device can use it to make sure some of
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+# its data is sent and loaded in the destination
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+# before doing switchover. This can reduce downtime
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+# if devices that support this capability are
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+# present. 'return-path' capability must be enabled
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+# to use it. (since 8.1)
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+#
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# Features:
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# @unstable: Members @x-colo and @x-ignore-shared are experimental.
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#
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@@ -492,7 +504,7 @@
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'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
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{ 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
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'validate-uuid', 'background-snapshot',
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- 'zero-copy-send', 'postcopy-preempt'] }
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+ 'zero-copy-send', 'postcopy-preempt', 'switchover-ack'] }
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##
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# @MigrationCapabilityStatus:
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--
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2.39.3
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