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Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function |
Date: |
Wed, 08 Aug 2018 09:27:31 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Peter Maydell <address@hidden> wrote:
D> On 7 August 2018 at 16:05, Juan Quintela <address@hidden> wrote:
>> Peter Maydell <address@hidden> wrote:
>>> So it's better to use a needed-always subsection, which will give
>>> the desired behaviour:
>>> * new QEMU -> new QEMU: state is always migrated
>>> * old QEMU -> new QEMU: migration doesn't fail, and guest
>>> will work assuming it didn't care about this corner of the
>>> device's functionality (the device will end up with state
>>> as it was at reset, or possibly special-cased via
>>> pre_load/post_load hooks for the "section not present" case)
>>
>> we break by definiton new QEMU -M <old machine type> into old QEMU.
>
> Is that supposed to work? I always thought that we never
> supported migration back to an older QEMU version like that.
It is a "best effort" case. As David told, downstream we try very
hard. For upstream we do when I found that, but not anywhere else.
> In any case, for all the devices here the machine types are
> not versioned.
This is part of the problem. For some architectures, we don't even care
about migraiton. For others, we care about migration but not
cross-version. And yet in others we care very much (downstream
specially).
And it is not clear what devices support each of them.
Later, Juan.
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, (continued)
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Juan Quintela, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Peter Maydell, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Peter Maydell, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Juan Quintela, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Peter Maydell, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Juan Quintela, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Peter Maydell, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Juan Quintela, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Peter Maydell, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Dr. David Alan Gilbert, 2018/08/07
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function,
Juan Quintela <=
- Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Peter Maydell, 2018/08/08
Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Dr. David Alan Gilbert, 2018/08/07
Re: [Qemu-devel] [PATCH] migration: Correctly handle subsections with no 'needed' function, Dr. David Alan Gilbert, 2018/08/07