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[PATCH 5/7] Implementation of vm_start() BH.
From: |
Andrey Gruzdev |
Subject: |
[PATCH 5/7] Implementation of vm_start() BH. |
Date: |
Wed, 18 Nov 2020 14:22:31 +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 1ffbb4ce4a..381da4a4d3 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 0/7] UFFD write-tracking migration/snapshots, Andrey Gruzdev, 2020/11/18
- [PATCH 7/7] Introduced simple linear scan rate limiting mechanism for write tracking migration., Andrey Gruzdev, 2020/11/18
- [PATCH 6/7] The rest of write tracking migration code., Andrey Gruzdev, 2020/11/18
- [PATCH 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 4/7] Implementation of write-tracking migration thread., Andrey Gruzdev, 2020/11/18
- [PATCH 3/7] Support UFFD write fault processing in ram_save_iterate()., Andrey Gruzdev, 2020/11/18
- [PATCH 1/7] Introduce 'track-writes-ram' migration capability., Andrey Gruzdev, 2020/11/18
- [PATCH 5/7] Implementation of vm_start() BH.,
Andrey Gruzdev <=
- Re: [PATCH 0/7] UFFD write-tracking migration/snapshots, no-reply, 2020/11/18