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[Qemu-devel] Re: new->old version migration
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: new->old version migration |
Date: |
Mon, 7 Feb 2011 23:52:03 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Feb 07, 2011 at 02:56:50PM -0600, Anthony Liguori wrote:
> On 02/07/2011 01:53 PM, Michael S. Tsirkin wrote:
> >On Mon, Feb 07, 2011 at 01:33:57PM -0600, Anthony Liguori wrote:
> >>On 02/07/2011 10:07 AM, Michael S. Tsirkin wrote:
> >>>New thread stated intentionally, the original patch is Message-ID:
> >>><address@hidden>
> >>>
> >>>On Thu, Feb 03, 2011 at 11:47:08AM +0530, Amit Shah wrote:
> >>>>Add a compat property for older machine types. When this is used (via
> >>>>-M pc-0.13, for example), the new flow control mechanisms will not be
> >>>>used. This is done to keep migration from a machine started with older
> >>>>type on a pc-0.14+ qemu to an older machine working.
> >>>>
> >>>>The property is named 'flow_control' and defaults to on.
> >>>>
> >>>>Reported-by: Alex Williamson<address@hidden>
> >>>>Signed-off-by: Amit Shah<address@hidden>
> >>>So, I think there are two things that need to be agreed on:
> >>>
> >>>- Can we commit to support migration from new qemu version to an old one?
> >>> We haven't in the past but downstreams do want this,
> >>> so it makes sense to have the infrastructure upstream.
> >>Only within a stable release series and only when it's possible
> >>without sacrificing integrity. I know some downstreams disagree
> >>with this but I don't think this is a business we want to get into.
> >>
> >>Regards,
> >>
> >>Anthony Liguori
> >>>- The infrastructure/command line option for such support.
> >>> We have the -M flags to describe the machine that
> >>> we are running, but that abstracts away guest-visible machine,
> >>> which the migration format is not.
> >>> Also, same qemu could migrate to any older version.
> >>> So I think we would have to add a flag (call it -V for now)
> >>> to savevm/migrate commands to specify the format to be used.
> >>> Naturally some machines would be incompatible with
> >>> specific -V values, that's nothing new.
> >>>
> >>>Pls comment.
> >OK, assuming we want this, let's talk about implementation.
> >I think that spreading custom flags all over the code like
> >this patch does would be pretty bad.
> >
> >What I'd like to see is a way to
> >- map stable versions (e.g. machine type if we are going
> > to tie to that) to savevm format using
> > some kind of table
> >- for save callbacks to be able to figure out what
> > version to use
>
> Why doesn't subsections already solve this problem?
>
> Regards,
>
> Anthony Liguori
How does it? We need to know we are saving in 0.13
format and skip the new subsection, otherwise
0.13 will see a subsection it does not recognize
and exit.
We also need API to add subsections without vmstate,
because virtio serial wasn't yet converted.
--
MST
- [Qemu-devel] new->old version migration, Michael S. Tsirkin, 2011/02/07
- [Qemu-devel] Re: new->old version migration, Alex Williamson, 2011/02/07
- [Qemu-devel] Re: new->old version migration, Anthony Liguori, 2011/02/07
- [Qemu-devel] Re: new->old version migration, Michael S. Tsirkin, 2011/02/07
- [Qemu-devel] Re: new->old version migration, Anthony Liguori, 2011/02/07
- [Qemu-devel] Re: new->old version migration,
Michael S. Tsirkin <=
- [Qemu-devel] Re: new->old version migration, Anthony Liguori, 2011/02/07
- [Qemu-devel] Re: new->old version migration, Michael S. Tsirkin, 2011/02/08
- [Qemu-devel] Re: new->old version migration, Amit Shah, 2011/02/08
- Re: [Qemu-devel] Re: new->old version migration, Anthony Liguori, 2011/02/08
- Re: [Qemu-devel] Re: new->old version migration, Amit Shah, 2011/02/08
- Re: [Qemu-devel] Re: new->old version migration, Anthony Liguori, 2011/02/08
- Re: [Qemu-devel] Re: new->old version migration, Michael S. Tsirkin, 2011/02/08