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Re: [Qemu-devel] [RFC 0/2] Disable hotplug during migration
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [RFC 0/2] Disable hotplug during migration |
Date: |
Wed, 29 Mar 2017 12:41:19 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) |
"Dr. David Alan Gilbert" <address@hidden> wrote:
> * Juan Quintela (address@hidden) wrote:
>> Hi
>>
>> This series disable hotplug/unplug during migration. Thank to Markus
>> for explaining where I had to put the checks. Why? Because during
>> migration we will fail if there are changes. For instance, in
>> postcopy, if we add a memory region, we would failing. Same for other
>> devices if they are not setup exactly the same on destination.
>>
>> Iidea would be to disable it, andthen enable for the thing that we know that
>> work.
>>
>> This series are on top of my previous RAMState v2 serie.
>>
>> Commets, please?
>
> So I think this is probably a good idea, but we should ask Li Zhijian who
> added
> migration_bitmap_extend if the reason for adding it was because they
> needed the hot add to work.
> cc'd.
I guess that the problem for them is that the bitmap size was wrong
after memory resizing. But I don't know if this has ever worked.
> IMHO we really need a 'configuration change mutex' that you can take
> to stop any changes in the VM hardware, and that would probably reduce
> a lot of the places that hold the BQL for just stopping changes.
That was the previous patch. With that one, you can't add/remove
hardware during migration.
Later, Juan.