From: Peter Xu <peterx@redhat.com>
To: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
Cc: Juan Quintela <quintela@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
qemu-devel@nongnu.org,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, Den Lunev <den@openvz.org>
Subject: Re: [PATCH v3 5/7] implementation of vm_start() BH
Date: Thu, 19 Nov 2020 13:46:24 -0500 [thread overview]
Message-ID: <20201119184624.GD6538@xz-x1> (raw)
In-Reply-To: <20201119125940.20017-6-andrey.gruzdev@virtuozzo.com>
On Thu, Nov 19, 2020 at 03:59:38PM +0300, Andrey Gruzdev wrote:
> 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.
There's a nice comment in previous patch about this before the bottom half
created, thanks, that's helpful. Though IMHO this patch can directly be
squashed into previous one, since it's confusing with the comment there but
without doing anything about it.
--
Peter Xu
next prev parent reply other threads:[~2020-11-19 18:48 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 12:59 [PATCH v3 0/7] UFFD write-tracking migration/snapshots Andrey Gruzdev via
2020-11-19 12:59 ` [PATCH v3 1/7] introduce 'track-writes-ram' migration capability Andrey Gruzdev via
2020-11-19 18:51 ` Peter Xu
2020-11-19 19:07 ` Peter Xu
2020-11-20 11:35 ` Andrey Gruzdev
2020-11-24 16:55 ` Dr. David Alan Gilbert
2020-11-24 17:25 ` Andrey Gruzdev
2020-11-20 11:32 ` Andrey Gruzdev
2020-11-19 12:59 ` [PATCH v3 2/7] introduce UFFD-WP low-level interface helpers Andrey Gruzdev via
2020-11-19 18:39 ` Peter Xu
2020-11-20 11:04 ` Andrey Gruzdev
2020-11-20 15:01 ` Peter Xu
2020-11-20 15:43 ` Andrey Gruzdev
2020-11-24 17:57 ` Dr. David Alan Gilbert
2020-11-25 8:11 ` Andrey Gruzdev
2020-11-25 18:43 ` Dr. David Alan Gilbert
2020-11-25 19:17 ` Andrey Gruzdev
2020-11-19 12:59 ` [PATCH v3 3/7] support UFFD write fault processing in ram_save_iterate() Andrey Gruzdev via
2020-11-19 18:25 ` Peter Xu
2020-11-20 10:44 ` Andrey Gruzdev
2020-11-20 15:07 ` Peter Xu
2020-11-20 16:15 ` Andrey Gruzdev
2020-11-20 16:43 ` Peter Xu
2020-11-20 16:53 ` Andrey Gruzdev
2020-11-23 21:34 ` Peter Xu
2020-11-24 8:02 ` Andrey Gruzdev
2020-11-24 15:17 ` Peter Xu
2020-11-24 17:40 ` Andrey Gruzdev
2020-11-25 13:08 ` Dr. David Alan Gilbert
2020-11-25 14:40 ` Andrey Gruzdev
2020-11-25 18:41 ` Dr. David Alan Gilbert
2020-11-25 19:12 ` Andrey Gruzdev
2020-11-19 12:59 ` [PATCH v3 4/7] implementation of write-tracking migration thread Andrey Gruzdev via
2020-11-19 18:47 ` Peter Xu
2020-11-20 11:41 ` Andrey Gruzdev
2020-11-19 12:59 ` [PATCH v3 5/7] implementation of vm_start() BH Andrey Gruzdev via
2020-11-19 18:46 ` Peter Xu [this message]
2020-11-20 11:13 ` Andrey Gruzdev
2020-11-19 12:59 ` [PATCH v3 6/7] the rest of write tracking migration code Andrey Gruzdev via
2020-11-19 12:59 ` [PATCH v3 7/7] introduce simple linear scan rate limiting mechanism Andrey Gruzdev via
2020-11-19 20:02 ` Peter Xu
2020-11-20 12:06 ` Andrey Gruzdev
2020-11-20 15:23 ` Peter Xu
2020-11-24 16:41 ` [PATCH v3 0/7] UFFD write-tracking migration/snapshots Dr. David Alan Gilbert
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