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[PATCH v2 5/7] Implementation of vm_start() BH.
From: |
Andrey Gruzdev |
Subject: |
[PATCH v2 5/7] Implementation of vm_start() BH. |
Date: |
Wed, 18 Nov 2020 16:20:46 +0300 |
To avoid saving updated versions of memory pages we need
to start tracking RAM writes before we resume operation of
vCPUs. This sequence is especially critical for virtio device
backends whos VQs are mapped to main memory and accessed
directly not using MMIO callbacks.
One problem is that vm_start() routine makes calls state
change notifier callbacks directly from itself. Virtio drivers
do some stuff with syncing/flusing VQs in its notifier routines.
Since we poll UFFD and process faults on the same thread, that
leads to the situation when the thread locks in vm_start()
if we try to call it from the migration thread.
The solution is to call ram_write_tracking_start() directly
from migration thread and then schedule BH for vm_start.
Signed-off-by: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
---
migration/migration.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/migration/migration.c b/migration/migration.c
index 158e5441ec..dba388f8bd 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3716,7 +3716,13 @@ static void *migration_thread(void *opaque)
static void wt_migration_vm_start_bh(void *opaque)
{
- /* TODO: implement */
+ MigrationState *s = opaque;
+
+ qemu_bh_delete(s->wt_vm_start_bh);
+ s->wt_vm_start_bh = NULL;
+
+ vm_start();
+ s->downtime = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - s->downtime_start;
}
/*
--
2.25.1
- [PATCH v2 0/7] UFFD write-tracking migration/snapshots, Andrey Gruzdev, 2020/11/18
- [PATCH v2 2/7] Introduced UFFD-WP low-level interface helpers. Implemented support for the whole RAM block memory protection/un-protection. Higher level ram_write_tracking_start() and ram_write_tracking_stop() to start/stop tracking memory writes on the whole VM memory., Andrey Gruzdev, 2020/11/18
- [PATCH v2 3/7] Support UFFD write fault processing in ram_save_iterate()., Andrey Gruzdev, 2020/11/18
- [PATCH v2 7/7] Introduced simple linear scan rate limiting mechanism for write tracking migration., Andrey Gruzdev, 2020/11/18
- [PATCH v2 1/7] Introduce 'track-writes-ram' migration capability., Andrey Gruzdev, 2020/11/18
- [PATCH v2 5/7] Implementation of vm_start() BH.,
Andrey Gruzdev <=
- [PATCH v2 4/7] Implementation of write-tracking migration thread., Andrey Gruzdev, 2020/11/18
- [PATCH v2 6/7] The rest of write tracking migration code., Andrey Gruzdev, 2020/11/18
- Re: [PATCH v2 0/7] UFFD write-tracking migration/snapshots, Eric Blake, 2020/11/18
- Re: [PATCH v2 0/7] UFFD write-tracking migration/snapshots, Andrey Gruzdev, 2020/11/19