From: David Hildenbrand <david@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>,
Juan Quintela <quintela@redhat.com>,
Pankaj Gupta <pankaj.gupta@cloud.ionos.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
teawater <teawaterz@linux.alibaba.com>,
qemu-devel@nongnu.org,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Alex Williamson <alex.williamson@redhat.com>,
Marek Kedzierski <mkedzier@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>,
Wei Yang <richard.weiyang@linux.alibaba.com>
Subject: Re: [PATCH v2 5/6] migration/postcopy: Handle RAMBlocks with a RamDiscardManager on the destination
Date: Thu, 29 Jul 2021 14:14:41 +0200 [thread overview]
Message-ID: <de4bd533-efaa-a6e5-c73c-01016d0f229c@redhat.com> (raw)
In-Reply-To: <YPs+cO7u1eXMomE0@t490s>
On 24.07.21 00:10, Peter Xu wrote:
> On Fri, Jul 23, 2021 at 09:01:42PM +0200, David Hildenbrand wrote:
>> It can happen in corner cases and is valid: with the current virtio-mem
>> spec, guests are allowed to read unplugged memory. This will, for example,
>> happen on older Linux guests when reading /proc/kcore or (with even older
>> guests) when dumping guest memory via kdump. These corner cases were the
>> main reason why the spec allows for it -- until we have guests properly
>> adjusted such that it won't happen even in corner cases.
>>
>> A future feature bit will disallow it for the guest: required for supporting
>> shmem/hugetlb cleanly. With that in place, I agree that we would want to
>> warn in this case!
>
> OK that makes sense; with the page_size change, feel free to add:
I just realized that relying on the page_size would be wrong.
We migrate TARGET_PAGE_SIZE chunks and the offset might not be page_size
aligned. So if we were to replace TARGET_PAGE_SIZE by rb->page_size, we
might accidentally cover a "too big" range.
Makes sense?
>
> Reviewed-by: Peter Xu <peterx@redhat.com>
>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-07-29 12:15 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 9:27 [PATCH v2 0/6] migration/ram: Optimize for virtio-mem via RamDiscardManager David Hildenbrand
2021-07-21 9:27 ` [PATCH v2 1/6] memory: Introduce replay_discarded callback for RamDiscardManager David Hildenbrand
2021-07-23 16:34 ` Peter Xu
2021-07-21 9:27 ` [PATCH v2 2/6] virtio-mem: Implement replay_discarded RamDiscardManager callback David Hildenbrand
2021-07-23 16:34 ` Peter Xu
2021-07-21 9:27 ` [PATCH v2 3/6] migration/ram: Handle RAMBlocks with a RamDiscardManager on the migration source David Hildenbrand
2021-07-21 9:27 ` [PATCH v2 4/6] virtio-mem: Drop precopy notifier David Hildenbrand
2021-07-23 16:34 ` Peter Xu
2021-07-21 9:27 ` [PATCH v2 5/6] migration/postcopy: Handle RAMBlocks with a RamDiscardManager on the destination David Hildenbrand
2021-07-23 16:34 ` Peter Xu
2021-07-23 18:36 ` David Hildenbrand
2021-07-23 18:52 ` Peter Xu
2021-07-23 19:01 ` David Hildenbrand
2021-07-23 22:10 ` Peter Xu
2021-07-29 12:14 ` David Hildenbrand [this message]
2021-07-29 15:52 ` Peter Xu
2021-07-29 16:15 ` David Hildenbrand
2021-07-29 19:20 ` Peter Xu
2021-07-29 19:22 ` David Hildenbrand
2021-07-21 9:27 ` [PATCH v2 6/6] migration/ram: Handle RAMBlocks with a RamDiscardManager on background snapshots David Hildenbrand
2021-07-23 16:37 ` Peter Xu
2021-07-22 11:29 ` [PATCH v2 0/6] migration/ram: Optimize for virtio-mem via RamDiscardManager Dr. David Alan Gilbert
2021-07-22 11:43 ` David Hildenbrand
2021-07-23 16:12 ` Peter Xu
2021-07-23 18:41 ` David Hildenbrand
2021-07-23 22:19 ` Peter Xu
2021-07-27 9:25 ` David Hildenbrand
2021-07-27 17:10 ` Peter Xu
2021-07-28 17:39 ` David Hildenbrand
2021-07-28 19:42 ` Peter Xu
2021-07-28 19:46 ` David Hildenbrand
2021-07-28 20:19 ` Peter Xu
2021-07-29 8:14 ` David Hildenbrand
2021-07-29 16:12 ` Peter Xu
2021-07-29 16:19 ` David Hildenbrand
2021-07-29 19:32 ` Peter Xu
2021-07-29 19:39 ` David Hildenbrand
2021-07-29 20:00 ` Peter Xu
2021-07-29 20:06 ` David Hildenbrand
2021-07-29 20:28 ` Peter Xu
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