Re: [PATCH] target/i386: always create kvmclock device

[Antoine Damhet <antoine.damhet@blade-group.com>]

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On Thu, Sep 17, 2020 at 03:42:37PM +0100, Dr. David Alan Gilbert wrote:

[...]

> > >
> > > Shouldn't the old check used when machine type <= 5.1 in order to avoid
> > > migration incompatibility ?
> > 
> > Hm, when the check fails we just don't create the device and no error is
> > reported, so even if we have kvmclock data in the migration stream but
> > fail to create it migration will still succeed, right? (not a migration
> > expert here :-)
> 
> When the migration stream is parsed, it'll try and find a "kvmclock"
> device to pass the data it's reading to; if one doesn't exist it'll
> fail.
> 
> The other question is in the incoming direction from an older VM;
> you'll have a kvm clock created here, but you won't load the kvm clock
> state from the migration stream - what is this clock going to do?

I guess that if the migration succeed (and the VMState keeps it's
initial value) the timestamp will be restored to 0 which is the current
behavior.

> 
> Dave


[...]

-- 
Antoine 'xdbob' Damhet

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