[libvirt] [PATCH 3/4] qemu: Filter CPU features when using host CPU

[Pavel Hrdina]

On Tue, Oct 17, 2017 at 01:15:43PM +0200, Jiri Denemark wrote:
> On Tue, Oct 17, 2017 at 12:57:10 +0200, Pavel Hrdina wrote:
> > On Wed, Oct 11, 2017 at 12:11:16PM +0200, Jiri Denemark wrote:
> > > The host CPU definition from host capabilities may contain features
> > > unknown to QEMU. Thus whenever we want to use this CPU definition, we
> > > have to filter the unknown features.
> > 
> > Might be nice to explicitly mention in the commit message that this
> > fixes the issue while reconnecting to QEMU process started by old
> > libvirt that keeps "host-model" in the status XML.  Took me some time
> > to figure that out :).
> 
> Yeah, sorry about it. What about the following commit message?
> 
> When reconnecting to a domain started with a host-model CPU which was
> started by old libvirt that did not replace host-model with the real CPU
> definition, libvirt replaces the host-model CPU with the CPU from
> capabilities (because this is what the old libvirt did when it started
> the domain). Without this patch libvirt could use features unknown to
> QEMU in the CPU definition which replaced the original host-model CPU.
> Such domain would keep running just fine, but any attempt to migrate it
> will fail and once the domain is saved or snapshotted, restoring it
> would fail too.
> 
> In other words whenever we want to use this CPU definition, we have to
> filter the unknown features.

Reviewed-by: Pavel Hrdina <phrdina at redhat.com>
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