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From: Peter Xu <peterx@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>,
	qemu-devel@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>,
	Markus Armbruster <armbru@redhat.com>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Den Lunev <den@openvz.org>, Paolo Bonzini <pbonzini@redhat.com>,
	Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
Subject: Re: [PATCH v13 0/5] UFFD write-tracking migration/snapshots
Date: Thu, 11 Feb 2021 22:06:21 -0500	[thread overview]
Message-ID: <20210212030621.GF157159@xz-x1> (raw)
In-Reply-To: <4E588B57-AAC8-40DD-9260-541836074DB3@redhat.com>

On Thu, Feb 11, 2021 at 10:09:58PM +0100, David Hildenbrand wrote:
> The issue is when the discard happened before starting the snapshot. Write-protection won‘t work and the zeroed content won‘t be retained in the snapshot.

I see what you mean now, and iiuc it will only be a problem if init_on_free=1.
I think CONFIG_INIT_ON_FREE_DEFAULT_ON should be off for most distros, so the
impact should be small, I think.  I thought about it, but indeed I didn't see a
good way to fix this if without fixing the zero page copy for live snapshot.

-- 
Peter Xu



  reply	other threads:[~2021-02-12  3:07 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-21 15:24 [PATCH v13 0/5] UFFD write-tracking migration/snapshots andrey.gruzdev--- via
2021-01-21 15:24 ` [PATCH v13 1/5] migration: introduce 'background-snapshot' migration capability andrey.gruzdev--- via
2021-01-21 15:24 ` [PATCH v13 2/5] migration: introduce UFFD-WP low-level interface helpers andrey.gruzdev--- via
2021-01-21 15:24 ` [PATCH v13 3/5] migration: support UFFD write fault processing in ram_save_iterate() andrey.gruzdev--- via
2021-01-21 15:24 ` [PATCH v13 4/5] migration: implementation of background snapshot thread andrey.gruzdev--- via
2021-01-28 18:29   ` Dr. David Alan Gilbert
2021-01-29  8:17     ` Andrey Gruzdev
2021-01-21 15:24 ` [PATCH v13 5/5] migration: introduce 'userfaultfd-wrlat.py' script andrey.gruzdev--- via
2021-02-09 12:37 ` [PATCH v13 0/5] UFFD write-tracking migration/snapshots David Hildenbrand
2021-02-09 18:38   ` Andrey Gruzdev
2021-02-09 19:06     ` David Hildenbrand
2021-02-09 20:09       ` Peter Xu
2021-02-09 20:31         ` Peter Xu
2021-02-11  9:21           ` Andrey Gruzdev
2021-02-11 17:18             ` Peter Xu
2021-02-11 18:15               ` Andrey Gruzdev
2021-02-11 16:19       ` Andrey Gruzdev
2021-02-11 17:32         ` Peter Xu
2021-02-11 18:28           ` Andrey Gruzdev
2021-02-11 19:01             ` David Hildenbrand
2021-02-11 20:31               ` Peter Xu
2021-02-11 20:44                 ` David Hildenbrand
2021-02-11 21:05                   ` Peter Xu
2021-02-11 21:09                     ` David Hildenbrand
2021-02-12  3:06                       ` Peter Xu [this message]
2021-02-12  8:52                         ` David Hildenbrand
2021-02-12 16:11                           ` Peter Xu
2021-02-13  9:34                             ` Andrey Gruzdev
2021-02-13 10:30                               ` David Hildenbrand
2021-02-16 23:35                               ` Peter Xu
2021-02-17 10:31                                 ` David Hildenbrand
2021-02-19  6:57                                 ` Andrey Gruzdev
2021-02-19  7:45                                   ` David Hildenbrand
2021-02-19 20:50                                   ` Peter Xu
2021-02-19 21:10                                     ` Peter Xu
2021-02-19 21:14                                       ` David Hildenbrand
2021-02-19 21:20                                         ` David Hildenbrand
2021-02-19 22:47                                           ` Peter Xu
2021-02-20  7:59                                             ` David Hildenbrand
2021-02-22 17:29                                               ` Peter Xu
2021-02-22 17:33                                                 ` David Hildenbrand
2021-02-22 17:54                                                   ` Peter Xu
2021-02-22 18:11                                                     ` David Hildenbrand
2021-02-24 16:56                                                       ` Andrey Gruzdev
2021-02-24 17:01                                                         ` David Hildenbrand
2021-02-24 17:52                                                           ` Andrey Gruzdev
2021-02-24 16:43                                     ` Andrey Gruzdev
2021-02-24 16:54                                       ` David Hildenbrand
2021-02-24 17:00                                         ` Andrey Gruzdev
2021-02-11 19:21     ` David Hildenbrand

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