From: mdroth <mdroth@linux.vnet.ibm.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Nicholas Thomas <nick@bytemark.co.uk>,
qemu-devel@nongnu.org, Juan Quintela <quintela@redhat.com>
Subject: Re: [Qemu-devel] (Another) 1.4.1 -> 1.5.0 migration failure
Date: Tue, 21 May 2013 17:07:33 -0500 [thread overview]
Message-ID: <20130521220733.GH2441@vm> (raw)
In-Reply-To: <CAFEAcA8_y_MbswkamHOge8b3nhM_S_6wo5CpOfi3pwZPGdEJzw@mail.gmail.com>
On Tue, May 21, 2013 at 10:16:48PM +0100, Peter Maydell wrote:
> On 21 May 2013 21:43, mdroth <mdroth@linux.vnet.ibm.com> wrote:
> > Makes sense, but apparently version IDs for incoming device state are
> > not allowed to exceed the destination's version, so we can't bump it
> > beyond the value in 1.5 without breaking migration from 1.5+ -> 1.5
>
> We care about backwards migration? That sounds like a pain.
As a best effort at least, hence subsections and whatnot, but not
always. This case for instance...
>
> > So I think our only option for version ID is to lock in the 1.5 value,
> > which seems to be 1936 (hopefully that's consistent across builds...).
>
> Yeah, I'm not convinced that's going to be consistent across builds,
> compilers, 64 vs 32 bit, etc etc etc. That's why I suggested a really
> high number.
Yah, it's more important to ensure old->new. Playing guessing games
about struct sizes to try to maintain new->old is likely to conflict
with that, so I guess we don't have much choice here. I'll send a patch
out shortly.
>
> thanks
> -- PMM
>
prev parent reply other threads:[~2013-05-21 22:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-21 11:33 [Qemu-devel] (Another) 1.4.1 -> 1.5.0 migration failure Nicholas Thomas
2013-05-21 11:55 ` Andreas Färber
2013-05-21 12:20 ` Nicholas Thomas
2013-05-21 16:55 ` mdroth
2013-05-21 17:26 ` mdroth
2013-05-21 17:50 ` Peter Maydell
2013-05-21 20:43 ` mdroth
2013-05-21 21:16 ` Peter Maydell
2013-05-21 22:07 ` mdroth [this message]
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